So, I’ve decided to try a slightly different approach for the next while—one that has these sorts of folks in mind. From time to time, you can still expect those more in-depth, technical articles, or perhaps a discussion of some new research that makes the popular press, or even an analysis of some new argument from the IDM or RTB. These will be breaks from the new routine, however. For the most part, we’re going to stick to the basics, much like you would if you took an introductory evolution course at a university. Don’t worry, though: this course doesn’t have any prerequisites! All that’s needed is a willingness to learn.

What you can expect

The goal of this course is straightforward: to provide evangelical Christians with a step-by-step introduction to the science of evolutionary biology.  This will provide benefits beyond just the joy of learning more about God’s wonderful creation. An understanding of the basic science of evolution is of great benefit for reflecting on its theological implications, since this reflection can then be done from a scientifically-informed perspective. From time to time we might comment briefly on some issues of theological interest (and suggest resources for those looking to explore those issues further), but for the most part, we’re going to focus on the science. For folks interested in the interaction between science and Christianity, I heartily recommend Ted Davis’ recent series as a fabulous introduction to the topic.

You can also expect a slow, patient pace. Since this course is intended for folks with little or no background in biology, we’re going to take our time to make sure no one gets left behind. This might be frustrating to folks who already know a fair bit about evolution. Hopefully even more knowledgeable readers will learn some new and interesting details along the way—but the goal will primarily be to help folks who are less well versed in evolution increase their understanding.

You can also expect a survey of many different areas that have some bearing on evolution. We’ll examine geology, paleontology, biogeography, genetics, and a host of other topics in order to provide a “big picture” overview. This broad-brush approach means that any given individual post will not necessarily be “convincing” to folks who have doubts about evolution. Think about assembling a large jigsaw puzzle: placing any individual piece, on its own, doesn’t convincingly demonstrate what the overall picture will show. This course will be like that. Each topic we cover will put a few pieces in place here and there, slowly building towards the final overall picture.

Since evolution is an active science, this process will also highlight where there are “missing pieces” that are still being sought by scientists. All of this is well and good, since the purpose of this course is not so much to convince anyone of the validity of evolutionary theory, but rather to inform readers about the nature and scope of evolution as a scientific theory in the present day. My goal is to provide readers with a basic understanding of what evolution is and how it works. Given that as the primary goal, if one finds the scope of the evidence ultimately convincing (or not) is somewhat beside the point. The intent here is to provide readers with information they can use to make their own, informed decision.

How you can help

First and foremost, you can help by spreading the word about this series to folks you think would be interested in learning more about evolution in a non-threatening environment. Secondly, you can help me by asking questions in the comments. One of the challenges of being a specialist is having the ability to put oneself in the shoes of someone just starting out. What might seem obvious to me may not seem obvious to you, and I hope you’ll feel that no question is too basic or too simplistic. If you’re wondering about something, it’s almost guaranteed that other folks are, too! So, please don’t be shy. I’ll do my best to answer questions in the comments, though I hope that some of our more skilled commenters will (respectfully!) help out here, as well. Finally, you can help by letting me know what broader areas of evolution you find confusing. I have my own ideas about what areas of evolution are commonly misunderstood, but I’d love to hear from readers about what areas they find difficult to understand. I’ll use this input to shape the topics I will cover as we go forward.

Getting started

In the next post in this course, we’ll dive into the course content by introducing two key areas: how scientific theories work in general, and how evolution in particular works as the current organizing theory of modern biology. 

Good science has an addiction to theories,¹ and for science to be good science, it must deal with good scientific theories.  What constitutes a good scientific theory?  That is a very involved question, but a user’s view of good scientific theories looks something like this:

1.  A scientific theory is not a guess or suspicion.  For example, “I have a theory about who shot President Kennedy,” reflects the colloquial meaning of the word “theory,” and not the meaning conveyed by scientists when they use the word “theory.”  
2. Scientific theories are convincing explanatory frameworks that efficiently integrate a large body of evidence about the world.  Good scientific theories have the capacity to make sense of a wide range of data that made less sense before the introduction of the theory. 
3. In order to be called a scientific theory, it must have been successfully tested and re-tested many times.²
4. A scientific theory must be falsifiable in order to be truly scientific.  The theory has to live constantly at risk from new data.³ 
5. A theory must have predictive power.⁴  Good theories allow scientists to make predictions based on the theory that, when tested, turn out to be at least roughly correct. 

These are not the only characteristics of a scientific theory, but they probably represent the most important features for practitioners of science. 

If we hold contemporary evolutionary theory to these standards, how well does it do?  Since the inception of evolutionary theory by Charles Darwin in 1859 with the publication of On the Origin of Species, there are four characteristics of evolutionary theory that have endured 150 years of further research:

1. Living species are descendants of other species that lived in the past.
2. These past species lived in populations that underwent gradual transformation so that the individuals in these populations changed their appearance, behaviors, metabolisms, and life histories over long spans of time.⁵
3. New forms of life arose by means of a process called speciation in which one lineage splits into two distinct lineages.  This continual splitting of organismal lineages leads to a nested genealogy of species.  This nested genealogy forms a veritable tree of life, whose root represents the first species to arise and whose twigs represent the millions of species living today.  If you trace back any pair of twigs from the modern species you will find that their histories merge at some node on the tree where the two species share a common ancestor.⁶ 
4. This process of biological change that takes place throughout the advance of geologic time, or evolution, occurs by means of variation in organisms (which we know today is due to genetic mutations) that is acted on by either random genetic drift or natural selection. Those individuals with variations better suited to the current environment leave more offspring, thus changing the average appearance of the population over time and making it a better fit to the environment. This improving fit between organisms and their environment gives the appearance of organisms having been well designed for their milieu.⁷ 

What is the evidence for these aspects of evolutionary theory?  The evidence is actually immense, but I will restrict this discussion to just a few items. 

First there is the fossil record. If life results from a natural process such as biological evolution, then we should observe a progression of fossil organisms that proceed from relatively simple, single-celled organisms in the oldest rocks to more complex, multicellular organisms in younger rocks. When paleontologists examine the geologic column, they perceive that some of the oldest and deepest layers of the geologic column contain fossils of microorganisms, and then marine invertebrates in younger layers above those,⁸ and then much later and higher up in the geologic column fish appear, followed later and higher still by amphibians, and then by reptiles, mammals, and birds.⁹  Thus, the general presentation of the fossil record in the rock record comports exactly with what the theory of evolution predicts. 

However, the fossil story gets even better, because scientists can trace evolutionary trends throughout the fossil record.  For example, horses get bigger, fuse their leg bones and toes into a single bone with a thick hoof and grow the thickness of their tooth enamel;¹⁰ Cenozoic brachiopod shells get narrower, decrease their rib numbers and beak angle;¹¹ diatoms get bigger;¹² and primate fossils reduce the size of their teeth and expand the size of their brains.¹³ 

Additionally, Darwin predicted that there should be organisms preserved in the fossil record that possess features found in two different types of creatures. Such organisms are “transitional forms” that bridge the gap between different types of organisms.¹⁴ However, the fossil record of Darwin’s time provided little evidence of such transitional forms.¹⁵ Therefore, Darwin gambled that future paleontological research would provide sufficient evidence to corroborate his theory. How did this gamble turn out? Since Darwin’s time, paleontologists have discovered transitional fossils that are part fish and tetrapod,¹⁶ part amphibian and part reptile,¹⁷ part dinosaur and part bird,¹⁸ and part reptile and part mammal.¹⁹ Once again, we would predict such paleontological trends and the existence of such transitional fossils if life came about through a process of organic evolution. Clearly paleontological research since Darwin’s time has powerfully vindicated his theory. 

Please join us for part two of this post tomorrow, where we will discuss how signs of evolution can be detected in organisms living today, and how evidence from multifarious scientific fields—not just biology and paleontology—have bolstered the theory of evolution and added to our understanding of how natural selection works.

Notes

1. Ratzsch, Del. The Battle of Beginnings: Why Neither Side Is Winning the Creation-Evolution Debate. Downer’s Grove, WI: Intervarsity Press, 1996. pp. 104–119. 
2. Kitcher, Philip. Abusing Science: The Case Against Creationism. Cambridge, MA: MIT Press, 1983. pp. 45–54.
3. Ibid, 42–48.  .
4. Ratzsch, Del. Science and Its Limits: The Natural Sciences in Christian Perspective. Downer’s Grove, WI: Intervarsity Press, 2000. pp. 21–24. 
5. Hall, Brian K., and Benedikt Hallgrimsson. Strickberger’s Evolution. 5th ed. Burlington, MA: Jones and Bartlett, 2013. pp. 19–68. 
6. Kitcher, Philip. Living With Darwin: Evolution, Design, and the Future of Faith. New York: Oxford University Press, 2009. pp. 43–71. 
7. Futuyma, Douglas J. Evolution. 3rd ed. Sundbury, MA: Sinauer Associates, 2013. pp. 281–343. 
8. Valentine, James W. On the Origin of Phyla. Chicago: University of Chicago Press, 2006. pp. 429–464. 
9. Carroll, Robert L. Vertebrate Paleontology and Evolution. New York: W. H. Freeman and Company, 1990. 
10. MacFadden, “Horses, the Fossil Record, and Evolution,” 131–158; McFadden, Bruce J. “Fossil Horses from "Eohippus" (Hyracotherium) to Equus: Scaling, Cope's Law, and the Evolution of Body Size.” Paleobiology 12, no. 4 (1986): 355–69.; Prothero, Donald R., and R.M. Schoch, eds. The Evolution of Perissodactyls. New York: Clarendon Press, 1989. ; McFadden, Bruce J. Fossil Horses. Systematics, Paleobiology, and Evolution of the Family Equidae. Cambridge, Cambridge University Press, 1993. 
11. McNamara, Kenneth J. “Evolutionary Trends.” In Encyclopedia of Life Sciences (New York: Macmillan Publishers Ltd, 2001), pp. 1–7. 
12. Litchman, E., C. A. Klausmeier, and K. Yoshiyama. “Contrasting Size Evolution in Marine and Freshwater Diatoms.” Proceedings of the National Academy of Sciences USA 106, no. 8 (2009): 2665–2670.
13. Tattersall, Ian. The Fossil Trail: How We Know What We Think We Know About Human Evolution. New York: Oxford University Press, 2008. pp. 89–198. 
14. Darwin, Charles. On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life. London: Penguin Books, 1985. p. 292.
15. Hunt, Gene. “Evolution in Fossil Lineages: Paleontology and The Origin of Species.” Supplement American Naturalist 176 (2010): S61–S76. 
16. Clack, Jennifer A. Gaining Ground: The Origin and Evolution of Tetrapods. Bloomington, IN: Indiana University Press, 2002; Daeschler, Edward B., Neil H. Shubin, and Farish A. Jenkins, Jr. “A Devonian Tetrapod-Like Fish and the Evolution of the Tetrapod Body Plan,” Nature 440, no. 7085 (2006): 757–63; Shubin, Neil H., Edward B. Daeschler, and Farish A. Jenkins, Jr. “The Pectoral Fin of Tiktaalik roasae and the Origin of the Tetrapod Limb.” Nature 440, no. 7085 (2006).): 764–71; Downs, Jason P., Edward B. Daeschler, Farish A. Jenkins, and Neil H. Shubin. "The Cranial Endoskeleton of Tiktaalik roseae." Nature 455, no. 7215 (2008): 925–9. 
17. Carroll, Robert L. Vertebrate Paleontology and Evolution. New York: W. H. Freeman and Company, 1990. pp. 156–216. 
18. Shipman, Pat. Taking Wing: Archaeopteryx and the Evolution of Bird Flight. New York: Touchstone, 1998. pp. 169–244.  
19. Prothero, Donald R. Evolution: What the Fossils Say and Why It Matters. New York: Columbia University Press, 2007. pp. 271–297. 

Genesis 8:1: But God remembered Noah and all the wild animals and all the domestic animals that were with him in the ark. And God made a wind blow over the earth, and the waters subsided; 2 the fountains of the deep and the windows of the heavens were closed, the rain from the heavens was restrained, 3 and the waters gradually receded from the earth.

The Flood narrative of Genesis 7-9 has played a prominent role in science and religion debates for over three hundred years and gave rise in earlier centuries to geological theories such as old earth catastrophism. While literary studies have uncovered the chiastic structure of the Flood story (see Gordon Wenham, “The Coherence of the Flood Narrative” Vetus Testamentum 28 (1978):336-48) and with it the theological pivot point of the entire narrative (Gen. 8:1 – “And God remembered Noah…), much of the popular attention remains on the questions regarding details (Is there THAT much water in the world to cover ALL the mountains to a depth of 15 cubits? Could you really fit two or seven of every animal species in an ark that size?)

Looking at a smaller matter, we find at the beginning and the middle of the narrative indications of an ancient Near Eastern worldview. As the story is told, the flood was not merely the result of excessive rain, but actually the convergence of the waters above the earth with the waters below the earth. It is, as one translation puts it, as if the sluice gates at the deep and of the heavens were thrown open and water poured in from above and below. This is a consistent picture from the Old Testament of a three-tiered universe—a dome above the earth holding back the heavenly waters, a flat earth with water on its surface, and water under an earth which is held up by pillars.

That the story is told using the cosmology of its time should not be unduly unsettling, nor that the story is reinterpreted as new understandings of the universe come into favor. By way of example, consider John Calvin and his understanding of the structure of the universe. Although committed to the principle of sola Scriptura, Calvin recognized that the Bible would have been written in terms its original recipients would have understood.

Calvin inherited the medieval cosmology of his time, a way of viewing the world heavily influenced by Greek thought and one which was about to receive shocks from astronomers such as Copernicus and Galileo. But not just yet. Calvin still subscribed to the common conception of his day in which the four elements—earth, air, fire, and water—comprised the earthly sphere and possessed unique characteristics. The nature of air and fire was to rise, while the nature of earth and water is to sink. Earth, being heavier than water, should sink to the center of the cosmos and water should compose the next layer. Both earth and water are spherical, i.e., naturally form spherically around the cosmic center. Thus the heavier spherical element of earth should be encased entirely within the lighter spherical element of water.

Notice what this does to the flood story. For Calvin, the amazing thing is that the world isn’t constantly under water and subject to flooding. In the cosmology of Calvin’s day, it does not take an act of God to cause a universal flood, but rather an actively present and restraining hand of God to keep the waters back in everyday circumstances and make inundation by water something other than universal.

Obviously, Calvin was wrong. Or perhaps we should say that medieval cosmology was flawed and justifiably gave way to new conceptions of the universe. The answer is not to return to an ancient Near Eastern cosmology, but to reinterpret cautiously within new and better cosmologies and to pay closest attention to the text and the theology of scripture.

The geological and planetary sciences bring their own unique contributions and are of more interest than the latest expedition to discover the ark on Mt. Ararat. Is the flood story a universalization of a catastrophic regional event that burned itself into the psyche of ancient cultures in the Mediterranean basin? Various theories regarding a Black Sea venue for a catastrophic flood event are still in process of being sorted out. It’s intriguing. Or the question where the water on Planet Earth comes from? Was it always here as an emanation of vapors from the earth’s crust in its early formation, or has it accumulated over eons through the steady bombardment of earth by small, icy comets? It’s an intriguing scientific question that is in the midst of determination through testing.

Preaching Suggestions

When preaching on the story of the Flood, it is easy to get lost in the debates over particulars. As mentioned elsewhere, to tackle all the peripheral issues threatens to turn a sermon into a geology lecture. Other settings are better suited to addressing those questions, and those are best addressed open-endedly.

A brief explanation of ancient Near Eastern cosmology can be helpful to contextualize the story. If there are those who are tempted to think that a cosmology embedded in the Bible must be inspired and definitive, one can note that cosmology has changed by the New Testament. The Bible itself isn’t wed to a particular structure of the universe.

What is important is to keep the theology of the text front and center, and in that theology there are at least three non-negotiables from the flood narrative. First, human sin and violence threatens to undo a good creation (the flood is a de-creation event, a return of the waters mentioned in Genesis 1:2). Second, God remembers Noah, and never forgets his promises. Third, the end of the flood is a covenant with the whole earth regarding the stability and endurance of the natural order.

A common argument leveled against the theory of evolution is that scientists have not been able to produce the expected transitional fossils that show the change of one species into another. If evolution were true, wouldn’t there be instances of clear intermediary species, like, for example, a species that was half whale and half hippo to show the transition between those two? In this BioLogos podcast, Kelsey Luoma addresses this misconception about what a transitional fossil actually is. Rather than a mix between two related species, transitional fossils point back to the common ancestors that modern species share. The fact is that the number of transitional species is massive and it grows with each passing year. Given the rarity with which organisms are actually fossilized, the amazing thing is actually the completeness of the fossil record, not its incompleteness. The transitional species story strongly supports, and certainly does not disprove, evolutionary theory. ¹

1. To hear the full audio clips which have been referenced go to:

• Rational Response Debate with Kirk Cameron (from Way of the Masters)
• Behind the Scenes with Dr. Neil Shubin (from Cincinnati Museum Center)
• Mark Norell Publishes New Archaeopteryx Findings (from American Museum of Natural Sciences)
• Texas A&M Professor Discusses Findings of Autralopithecus Sediba and its Relationship to Humans (from Texas A&M University)
• Intro/outro music composed by Martin Minor (Minor2Go).

An audio only version of the podcast can be downloaded here.

The story in Genesis is a story (full of the deepest suggestion) about a magic apple of knowledge; but in the developed doctrine [of the Fall] the inherent magic apple has quite dropped out of sight, and the story is simply one of disobedience. I have the deepest respect even for Pagan myths, still more for myths in Holy Scripture. I therefore do not doubt that the version which emphasises the magic apple, and brings together the trees of life and knowledge, contains a deeper and subtler truth than the version which makes the apple simply and solely a pledge of obedience. But I assume that the Holy Spirit would not have allowed the latter to grow up in the Church and win the assent of great doctors unless it also was true and useful so far as it went. It is this version which I am going to discuss, because, though I suspect the primitive version to be far more profound, I know that I, at any rate, cannot penetrate its profundities.¹

Whatever its theological profundities, though, Lewis is clear that Genesis 2-3 is probably not a straightforward narrative of historical events. “What exactly happened when Man fell, we do not know,” he later writes. “We have no idea in what particular act, or series of acts, the self-contradictory, impossible wish [to be our own masters] found expression. For all I can see, it might have concerned the literal eating of a fruit, but the question is of no consequence.”²

What, then, is of consequence for Lewis, we might ask? The real story of the Fall, says Lewis, is not the surface narrative about “the magic apple,” but rather what he refers to as “the developed doctrine” of the Fall, namely the doctrine of humankind’s depraved condition:

According to [the doctrine of the Fall], man is now a horror to God and to himself and a creature ill-adapted to the universe not because God made him so but because he has made himself so by the abuse of his free will. To my mind this is the sole function of the doctrine.³

The “sole function of the doctrine” for Lewis is to name the human condition for what it is, namely, shot through with corruption. Or, as Lewis put it in A Preface to “Paradise Lost,” “The Fall is simply and solely Disobedience—doing what you have been told not to do: and it results from Pride—from being too big for your boots, forgetting your place, thinking that you are God.” You might call this the “Mere Depravity” view of the Fall.

Throughout The Problem of Pain Lewis displays a remarkable degree of comfort with evolutionary theory, not least evolutionary accounts of human origins. A corollary of Lewis’s acceptance of evolutionary theory, of course, is that death pre-existed humanity. Lewis grasps this nettle in chapter IX of the book when he writes,

The origin of animal suffering could be traced, by earlier generations, to the Fall of man—the whole world was infected by the uncreated rebellion of Adam. This is now impossible, for we have good reason to believe that animals existed long before men. Carnivorousness, with all that it entails, is older than humanity.⁵

Here is not the place to go into Lewis’s postulation that Satan was responsible for animal predation. We need only note that he makes this suggestion precisely in order to show how a broadly Darwinian picture of natural history may be compatible with a broadly Christian view of the world. For some, severing the link between the Fall of man and death’s entry into the world, is anathema. But given Lewis’ mere depravity view of the Fall, this evolutionary understanding of natural history creates no real problem for Christian faith.

Moreover, for Lewis the evolutionary picture of the ascent of humankind presents no real objection to the Christian doctrine of the Fall, either:

Many people think that this proposition [that we are fallen creatures] has been proved false by modern science. “We now know,” it is said, “that so far from having fallen out of a primeval state of virtue and happiness, men have slowly risen from brutality and savagery.” There seems to me to be a complete confusion here…. If by saying that man rose from brutality you mean simply that man is physically descended from animals, I have no objection. But it does not follow that the further back you go the more brutal–in the sense of wicked or wretched–you will find man to be.⁶

Lewis goes on to note that the categories of virtue and vice simply do not apply to the animal kingdom–and therefore not to our pre-human ancestors either–because animals as such are not moral agents. Moreover, Prehistoric man is not to be presumed to be altogether reprobate simply on account of using only rudimentary tools, hunting and gathering, and the like. Primitivity ought not to be confused with sinfulness he argues. Thus, for Lewis, the discoveries of modern paleontology and archaeology can tell us nothing about when or whether our ancestors fell from a state of innocence, and so we are free to accept, as Lewis seems to have, man’s physical descent from animals without giving up the Christian doctrine of the Fall.

While Lewis may not have publically argued for the historicity of Adam and Eve, his private opinions might have been another matter. In his recent essay “Darwin in the Dock,” John G. West has argued that, regardless of what he said in print, Lewis privately “embraced the literal existence of Adam and Eve.”⁷ West chiefly bases his argument for Lewis’s private belief in a literal Adam and Eve on an anecdote involving one of Lewis’ Oxford colleagues, Helen Gardner, recounted in A.N. Wilson’s C.S. Lewis: A Biography.⁸ Upon being asked at a dinner party whom he would most like to meet after death, Lewis replied, “Oh, I have no difficulty in deciding…. I want to meet Adam.” Gardner, it is reported, replied by saying that “if there really were, historically, someone whom we could name as ‘the first man’, he would be a Neanderthal ape-like figure, whose conversation she could not conceive of finding interesting.”⁹ Lewis, we are told, gruffly responded, “I see we have a Darwinian in our midst” and never invited Gardner to dinner again.¹⁰

West takes this tense little interaction between Lewis and Gardner to indicate that Lewis’ belief in a literal historical Adam and Eve. However, it should be noted that such a conclusion seems somewhat overhasty in light of what Lewis says in The Problem of Pain, where he articulates a view rather similar to what Gardner said that evening:

I do not doubt that if the Paradisal man could now appear among us, we should regard him as an utter savage, a creature to be exploited or, at best, patronised. Only one or two, and those the holiest among us, would glance a second time at the naked, shaggy-bearded, slow spoken creature: but they, after a few minutes, would fall at his feet.¹¹

Given that Lewis actually believed what he wrote here, the difference between Lewis and Gardner seems not to have been either the question of “whether man is physically descended from animals” (which, as we have seen, Lewis was willing to grant) or the question of whether Paradisal man would be a “naked, shaggy-bearded, slow spoken creature,” a “Neanderthal ape-like figure.” Rather they differed over whether “Paradisal man,” as Lewis puts it, would have been someone, however primitive, to be revered, or whether, as Gardner seemed to believe, a mere brute. Taking Lewis’ written statements at face-value, it would appear that his irritation with Gardner owed less to her acceptance of evolution than it did to her dismissive presumption that our forebears were but dull savages.

Finally, it should be noted that Lewis was not even committed to the most basic element of a belief in a literal Adam and Eve, namely, that it was precisely two humans who fell and from whence our species came. He writes, “We do not know how many of these creatures God made, nor how long they continued in the Paradisal state. But sooner or later they fell.”¹² Lewis’s mere depravity view of the Fall and his belief in the mythical character of the Eden story gave him some latitude on the question of whether the Fall consisted of a historic first human pair going wrong at an easily identifiable moment. For Lewis, it was apparently quite possible that whole tribes of “Paradisal” Prehistoric humans could have gone about their business for generations—hunting, gathering, singing around the campfire, rearing children, painting in caves—before the spiritual and scientifically undetectable catastrophe of “the Fall” occurred. In other words, if Lewis were presented with the recent genomic evidence which suggests that our species arose from an initial population of several thousand rather than only two, it is doubtful that it would have flustered him. It simply makes no difference to Lewis’s argument how or how many humans initially “fell.” All that matters for Lewis is that God made humans (perhaps via evolution, perhaps not) and that we humans have gone quite wrong–so wrong, in fact, that it is beyond our powers to repair ourselves. Mere Christianity, for Lewis, does not logically depend on the historicity of the Adam and Eve story, but on the doctrine of our mere depravity.

In tomorrow's concluding post, we turn to C.S. Lewis' views on the compatibility of evolution and Christian faith.

Notes

1. Lewis, The Problem of Pain, (New York: Simon & Schuster, 1996), 63-64, my italics
2. Ibid.
3. Ibid, my italics
4. Lewis, A Preface to Paradise Lost, (New York: Oxford University Press, 1961), 70-71
5. Lewis, The Problem of Pain, 119
6. Ibid, 64
7. West, “Darwin in the Dock,” in The Magician’s Twin: C.S. Lewis on Science, Scientism, and Society, (Seattle: Discovery Institute Press, 2012), 121. West’s volume takes a markedly different view of Lewis and Lewis’s legacy regarding debates about Christianity and evolution. I intend to write a thorough critical review of West’s book in the near future.
8. Ibid
9. A.N. Wilson, C.S. Lewis: A Biography, (New York: W.W. Norton, 1990), 210
10. Ibid
11. Ibid
12. Ibid.

This week we feature the third clip from the upcoming documentary “From the Dust”, directed by filmmaker Ryan Pettey. It is our sincere hope that, above all else, the film can become a focal point for some of the big questions that inevitably arise at the intersection of science and faith. We believe Ryan's work will inform faith and enrich discussion, and we feel that this week’s topic, the Fall, is of particular importance for Christians as we think through the ramifications of creation by evolutionary mechanisms.

To help foster such dialogue, we are once again including several discussion questions with this week’s clip. In the transcript below, you’ll find several prompts that are meant to help viewers dig deeper into the material being presented. Mouse over each highlighted region and a question will appear on the side. We encourage you to watch this video with your friends, your churches, your small groups and Sunday School classes, your pastors -- or anyone else for that matter – and take some time to discuss what is being said (and maybe even what isn’t). You may not all agree, but you will find yourselves engaged in fruitful and spirited conversation. And it is this kind of conversation that will help move the science and faith discussion forward.

The provided questions are just a few of the discussion questions that go with this transcript, and we'd be happy to send them to you to foster further conversation within your church or small group setting. If you’d like to see the questions, or if you have stories from your own small group discussions about the clip, we would love to hear from you at info@biologos.org.

Editor's Note: The full documentary is now available on DVD and Blu-ray. You can order the film here, and learn more about the project here.

“The Fall” Transcript

Dr. Jeff Schloss: “My friends and colleagues, who have concerns about evolutionary theory for theological reasons, are onto something, and one of them involves the Fall, the nature of the Fall, what it is. Even if it is a metaphor, it is a metaphor for something, and what is that something? And how would we make sense of that something in light of evolutionary theory? The other issue on this has been probably the most serious issue that not only Christians, but all theists who believe in a good and providential God have wrestled with, it is the problem of natural evil.”

Reverend Dr. Michael Lloyd: “The problem of evil is a real problem to religious faith. It was certainly the thing for Darwin himself. That is what made him question his faith, and I think rightly so. It does not look like the sort of system that a good and loving and benevolent God would have set up. Now, obviously that raises huge questions because we don’t see any evidence of a world that was harmonious. We only see evidence of a world that was at war with itself, and that obviously is the problem that Christian theologians face. For a long time I used to believe that the Genesis narratives paint a picture of a world completely at peace, completely harmonious until the human fall, and then something goes wrong. When I began to look at it more closely, I began to think that there is more to it than that. There is evidence from the text that things are already dislocated, already out of joint. For one thing, there is the serpent, and however you interpret the serpent, here is a bit of the created order that is actively talking against God, working against God—so there is already something that has gone wrong. Secondly, there is the command to fill the earth and subdue it. There is the suggestion that something needs to be subdued, something is not quite right that needs to be put right and humans beings are called to do that—to put it right. And thirdly, it is a garden. It is almost as if God has said, ‘Here is a little bit I have done for you, here is a little bit of order and harmony that I have done for you. Now you go and spread that order and that harmony throughout the rest of creation.’ The tragedy is, of course, that human beings don’t do that. Rather than put that right, they make it worse.”

Dr. Alister McGrath: “Clearly Scripture distinguishes humanity from the rest of creation by this idea of the image of God. And that is understood in a number of ways—one of which is relational. Human beings have this God-given capacity to be able to relate to God, which is simply not there for the rest of creation. How do we understand that phrase: the image of God? If we accept the narrative of biological evolution, we have to say that at some point humanity became sufficiently distinguished from the rest of the natural world to be able to have this relationship with God.”

Reverend Dr. Michael Lloyd: “If you have a very finely graded gas tap and you begin to turn it on, initially, there is not enough gas in the air for the gas to ignite. So, you turn it up some more, still nothing, a bit more, still nothing, and a bit more, still nothing. At a particular point, there will be enough gas to air ratio for the thing to ignite. So, you can have a completely smooth, upward development, and yet, you can have something decisive happening at a particular moment. You get an increase in that moral capacity and moral awareness; you get an increase in their relational ability, in their social ability. You get an increase in their tool-making ability. You get an increase in their language. At a particular point there is enough of all that. There is enough relational capacity; there is enough social capacity and moral awareness and spiritual awareness for God to deal with us in a new way: ‘They have enough creativity to reflect the fact that I am the creator. They have enough relational capacity to reflect the fact that I am love. This in some way reflects who I am, and I will stamp my image upon them.’”

Reverend Dr. John Polkinghorne: “As hominids evolved and became more complex, then self-consciousness, in the sense of projecting our minds into the remote future or past began to dawn in them. And that didn’t bring biological death into the world, because obviously it had been there for millions of years beforehand, but it brought into the world what you might call mortality. Because our ancestors were self-conscious, they knew they were going to die. Because they had turned away from God, they had alienated themselves to the only one who was the ground for the hope of a destiny beyond death. And so, mortality, meaning the sadness, the human sadness at transiency and decay dawned in human life. Another very subtle feature of the Genesis 3 story is that it is a fall upwards as people would sometimes say. It is the gaining of some knowledge, the knowledge of good and evil, the story says. And so, the dawning of self-consciousness is also the gaining of something that wasn’t there before. What the serpent whispers in Eve’s ear is, ‘eat this fruit, and you will be like God. You won’t need God anymore. You can do it yourself.’ That is the fundamental sin, the fundamental mistake in human life is believing that we can do it on our own, doing it my way, and spiritual death is to deliberately and persistently cut yourself off from that. It doesn’t occur as an angry God giving you a punishment for not falling into line. It is simply that you have punished yourself. You know, preachers sometimes say that the gates of hell are locked from the inside not to keep the creatures in, but to keep God out. And that, I think in the end, is what spiritual death is if you persist in it. But God is always, I am sure, at work, seeking to draw people back into the divine love. I think that is the work that is necessary to understand what Paul is getting at in Romans 5 when he says that death came into the world through one man. The cost of development is a degree of precariousness. The people need the grace of God if we truly are to live fulfilling lives.”

In 1774, the French chemist Antoine Lavoisier replicated the relevant experiments in more controlled ways to demonstrate that mass was conserved during combustion. He also renamed the part of the air that burned 'oxygène.' English scientists resisted the French scientist's new name, not least because the English Priestly had already published his discovery of the gas. 'Oxygen' nonetheless entered the common English vocabulary in part due to one of the first popular science books, The Botanic Garden (1791), which included a poem praising the gas using the preferred French name. By coincidence, this book also promoted some early ideas about biological evolution (specifically, it suggested that sexual reproduction might be important to evolution, which might help to explain the popularity of a book of poems about science). It was written by Erasmus Darwin, the grandfather of Charles Darwin, who first proposed the modern form of the theory of biological evolution in his 1859 book, On the Origin of Species.

150 years later, we are discovering that the lines connecting evolution and oxygen run deeper than the Darwin family tree. We now know, for instance, that for roughly half of the Earth's 4.6-billion-years of history, there was little to no oxygen in the atmosphere. Instead, oxygen entered the atmosphere in two major pulses, with one between 2.4 and 2.2 billion years ago, and another between 0.8 and 0.54 billion years ago. Recent evidence suggests that the first pulse may have actually been the largest event in a series of fits and starts beginning at around 2.7 billion years ago that finally produced a stable low oxygen atmosphere by around 1.8 billion years ago.

Remarkably, both episodes of atmospheric oxygenation happened just before explosions in biological diversity. We have spotty evidence of unicellular eukaryotes (cells with nuclei) before 2.4 billion years ago, but the first fossil evidence for large, diverse eukaryotic communities comes at 1.5 billion years ago. If you are a human, this is part of your history; humans are multicellular eukaryotes descended from one of these early unicellular pioneers. Multicellular animal life is an innovation that seems to have required more oxygen: animals don't appear in the fossil record until about 0.61 billion years ago, toward the end of the second pulse of oxygen.

It is, perhaps, not surprising that major evolutionary events in the eukaryotic family tree, including the origin and diversification of the animals, would be tied to or even driven by major changes in atmospheric oxygen abundance. Eukaryotes generally, and animals specifically, are oxygen lovers. As the subjects of Mayow and Priestly died to prove, we require oxygen for respiration. In general, the larger and more organizationally complex we are (for instance, a human versus a slime mold), the more oxygen we require.

But where did all the oxygen come from? Ultimately, it was produced by the bacterial equivalents of the plants in Joseph Priestley's experiment, a group of photosynthetic microbes called the cyanobacteria. These bacteria are the first and only organisms to have evolved the ability to produce oxygen by photosynthesis. In fact, plants are able to photosynthesize only because their cells harbor descendants of one of the early cyanobacteria. We call them chloroplasts and think of them as little cellular organs, but they are actually the great-great-great... granddaughters of a cyanobacterium that long ago gave up its independence in exchange for the stable environment inside a eukaryotic cell. In any case, photosynthesis is the only known geological process capable of producing oxygen at the rates required for the two pulses of atmospheric oxygenation. The first pulse was probably largely accomplished by cyanobacteria, while the second pulse was probably mostly associated with the cyanobacterial denizens of eukaryotic algae.

What is remarkable about all of this is the extent to which modern life and the atmosphere are products of each other's evolution. The tiniest of photosynthetic organisms played one of the most important roles in shaping the sky, and the sky helped to usher in the age of animals! As a Christian and a geobiologist, I do not believe that this relationship is anticipated or predicted by the Biblical creation accounts.

But then again, why should it have been? The original audience for these accounts would have found concepts like bacteria or even oxygen incomprehensible. The people for whom the Bible was originally addressed thought about origins primarily in terms of ongoing national conflicts and the current human condition. Faced with a variety of violent creation myths that reinforced national conflicts, Genesis said that the universe was created to be good, peaceful, and orderly by one god. It specifically listed things worshipped by other nations as creatures of that god, and in the climax of the creation account, Abraham was called by the same god to be a blessing to all the nations through Israel.

I am not claiming that the Bible cannot be read in a way that can shape us in real and meaningful ways today. In fact, for those who believe that the Bible is inspired, part of the meaning of inspiration has to be that the Bible is God's powerful word to both those with no concept of modern science (most of the world's population, both today and in the past) and to those deeply engaged in its practice. But, and this is a big but, we contemporary Americans read the Bible best when we are sensitive to the assumptions of the original audience, carefully observe how the Bible transformed those assumptions, and look for opportunities to do the same thing with our thinking.

I think that it is important for Christians to reflect on the view of origins that science has given us in light of the thinking evident in the Biblical creation accounts. We have to do this because science gives us a story that is inherently without philosophical or theological meaning; it is up to us to give it meaning by understanding it in relationship with our beliefs. For instance, some see the evolutionary history of life and the Earth and give that history meaning by elevating chance and necessity to the level of prime actors in their own modern creation account. This meaning is not inherent to the theory of evolution; it is supplied by an atheistic belief system external to the theory. I suggest that this view mistakes created things (chance and necessity) for the Creator.

Others have preferred to see the regularity of the universe as the action of an orderly God. This is an old approach to natural theology that was popular among many early scientists, and saw God as responsible for doing such things as maintaining the planets in consistent paths around the sun. Still others look for God in the unexplained. This is a newer approach that sees God as acting primarily in short bursts not explainable by the regular, orderly function of the universe. Looking for God in these ways is a little like trying to capture him in a bell jar, an approach that worked perfectly well with oxygen for Mayow, Priestley, and Lavoisier, but one that is unlikely to impress the Creator described in the Bible.

I prefer to see the same history in the light of a God who desires to share aspects of his nature with his creation, notably including his creativity. Just as he has made humans to be creators (with a little 'c'), he has given the rest of our world the gift of being instrumental in its own creation through the process of evolution. This surely must have been part of what God saw when he described his creation as good! It is my hope that the modern American church can learn to see the goodness of creation in things like the evolutionary history of life and the atmosphere, as well.

This post first appeared in October 2009

Dr. Thompson responded that while the essence of Sin is ultimately mysterious, he suggests that there are some ways to think about Sin in the language of interpersonal neurobiology.

On the other hand, Dr. Smith found the wisdom of St. Augustine in The Confessions quite helpful—The essence of Sin is loving the wrong things in the wrong ways. It’s a disordered love.

We need to have an account of Sin in terms of habit. A lot of Christians today think of “sins” and discreet choices, but historically Christians have thought of Sin as a habitual tendency and disordering. It is formed over time—that’s what a vice is. Virtue and sanctification require ongoing re-habituation, a counter-formation of our inclinations.

Dr. Thompson followed up with a reference to Malcolm Gladwell’s Outliers and noted that people who are really good at what they do generally acquire it through lots of practice. Thompson then asked the audience, “How are we, in an embodied way, going to practice Christianity for 10,000 hours?”

We hope you have enjoyed this video series. If you'd like to learn more, we encourage you to read Curt Thompson's The Anatomy of the Soul and James K.A. Smith's Desiring the Kingdom: Worship, Worldview, and Cultural Formation. Dr. Smith also has a new book coming out this winter entitled Imagining the Kingdom: How Worship Works. ]]> Fri, 05 Oct 12 04:00:00 -0700 Curt Thompson, Smith, James K.A. http://biologos.org/blog/science-and-the-bible-theistic-evolution-part-4?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/science-and-the-bible-theistic-evolution-part-4?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication Scientist-theologians who write about TE also think about creation and theodicy in terms of divine “kenosis” and eschatology. So today we’ll conclude our “implications” section by returning to creational theology, and then turn to the ways TEs re-think Adam and Eve in light of human evolution. Some implications and conclusions of Theistic Evolution—continued again

Last time I introduced the idea that a Christocentric theology of creation is one of the hallmarks of Theistic Evolution, and I focused on the idea of the “Crucified God.” But the scientist-theologians who write about TE also think about creation and theodicy in terms of divine “kenosis” and eschatology. So today we’ll conclude our “implications” section by returning to creational theology, and then turn to the ways TEs re-think Adam and Eve in light of human evolution.

Kenosis, theodicy and eschatology

John Polkinghorne and others, citing Philippians 2:7, like to speak about divine “kenosis”, God’s choice to “empty himself” in taking on human form; they apply this also to the act of creating the world in a great work of self-sacrificial love. Although Wikipedia gives much information about the roots of this doctrine in Orthodox and Catholic circles, my knowledge is minimal and I cannot confirm what I find there (though it might all be correct). According to a theologian I once consulted, kenosis in soteriology was discussed by Lutherans in the 17th century (if not perhaps even earlier, by others), but was only extended to theology of creation in recent decades. The most I can say with confidence is this: one of the most striking features of Protestant thought about nature, during and since the Scientific Revolution, is the degree to which it is not Christocentric in the sense we are now discussing. In much Protestant and Evangelical literature devoted to the topic of creation, one often looks in vain even for references to Jesus, let alone to Jesus as the suffering servant through whom the world was made,. Only in the latter part of the 20th century do I find a clear emphasis on the idea that nature is the creation of the God who put aside power and was crucified. If this understanding is correct, then I would say that it’s high time, and let’s get on with it!

TEs (especially Polkinghorne) are also in the forefront of those Christian writers who are linking theodicy inextricably with eschatology. Yet another scientist-theologian, Robert Russell, offers this powerful eschatological vision in Cosmology From Alpha to Omega, drawing on all of the main ideas I’ve presented in this section:

[I]n order to move us beyond mere kenosis to genuine eschatology, I believe that both kenotic theology and eschatology must be structured on a trinitarian doctrine of God. The reason here is simple: it is the trinitarian God who will act to bring about the redemption of all of nature since it is this God who is revealed as God in and through the cross and resurrection of Jesus. A kenotic theodicy (that God suffers voluntarily with the world) in and of itself is not redemptive. Eschatology is required, in which the Father who suffers the death of the Son acts anew at Easter to raise Jesus from the dead. In turn, the involuntary suffering of all of nature--each species and each individual creature--must be taken up into the voluntary suffering of Christ on the cross (theopassionism) and through it the voluntary suffering of the Father (patripassionism).(p. 266)

George MacDonald (source)

Because this series is primarily focused on the history of approaches to understanding Science and the Bible, I will not delve more deeply into these important theological issues, but only direct readers to resources such as these. Still, I close this section with a quotation from George MacDonald’s Unspoken Sermons, the same passage that C. S. Lewis used in abbreviated form as an epigram for The Problem of Pain:

“the Son of God, who, instead of accepting the sacrifice of one of his creatures to satisfy his justice or support his dignity, gave himself utterly unto them, and therein to the Father by doing his lovely will; who suffered unto the death, not that men might not suffer, but that their suffering might be like his, and lead them up to his perfection...”

Adam, the fall, and sin

(5) TEs have to confront questions about human origins that are much easier for OECs or YECs to answer: Did Adam and Eve really exist as historical persons? Was the “fall” an actual historical event? If not, what is the origin of sin?

Michelangelo Buonarroti, “The Fall and Expulsion from the Garden of Eden,” Cappella Sistina, Vatican (1509-10)

My comments here are much briefer, but I don’t mean to imply that the questions are any less important than the one I’ve just dealt with. Polkinghorne does not hold a traditional view of the fall, but he likes Reinhold Niebuhr’s view “that original sin is the only empirically verifiable Christian doctrine!” (Belief in God in an Age of Science, p. 88) This reminds me of G. K. Chesterton, who famously remarked, “Certain new theologians dispute original sin, which is the only part of Christian theology which can really be proved” (Orthodoxy, chap. 2). In other words, anyone who doubts the idea that we are “fallen” creatures simply needs to look around—that is all the evidence of our strong bent to wickedness that you’ll ever need.

There are ways to finesse the fall and evolution in a quasi-concordistic manner, such as the “headship” model advocated by Denis Alexander. Others reject any appeal to Concordism, stressing the principle of divine accommodation. For example, Denis Lamoureux argues that in the revelatory process the Holy Spirit came down to the level of understanding of the ancient Hebrews and used their ancient conception of de novo creation, in which humans were created quickly and completely. Thus, in Genesis chapters 2 and 3, Adam and Eve are ancient vessels that deliver the inerrant spiritual truths that God created us and that we are sinners.

The views that have received the most attention among evangelicals, however, are probably those of biblical scholar Peter Enns, particularly his new book, The Evolution of Adam. Instead of trying to summarize them myself, I’ll link his discussion of “Mistakes in the Adam/Evolution Discussion”, since it parallels some of the content in the book. Also see his replies to some evangelical scholars who have been critical of the book.

One of the most original and thoughtful proposals I have seen comes from philosopher Robin Collins (for bibliographical information on this and the other works cited in the rest of this column, see below). Collins calls his model the “Historical/Ideal” view, because “the original state described in the Garden story represents an ideal state that was never realized,” showing “what an ideal relation with God would be like.” Adam and Eve represent every person who has ever lived, but they also represent “the first hominids, or group of hominids, who had the capacity for free choice and self-consciousness.” Just as the first hominids made sinful choices, so do we now, and original sin involves “the resulting bondage to sin and spiritual darkness that is inherited from our ancestors and generated by our own choices.” I can’t convey the subtlety and thoroughness of this account in a short space, so those who want to know more will have to read for themselves. Conveniently, Collins provides a link to a “near final version” of his paper on his web site. If someone wants to summarize his arguments in a few paragraphs below, it would be a real service to our “course.”

Problems with historicity

(6) Questions about the historicity of Adam & Eve are underscored by evolution, but they would still come up even if Darwin had never existed and no one had ever proposed that humans and other animals have common ancestors. The Bible places Adam & Eve in a Neolithic world, with cities and agriculture, whereas non-biological scientific evidence shows that humans existed for a very long time before cities or agriculture came into existence.

Read that again. It’s a crucial point. Far too many people believe—erroneously—that evolution is responsible for undermining the historicity of Adam, Eve, and the Garden of Eden. In fact, the relevant science here is almost entirely from anthropology, not biology, and it involves human antiquity, not common ancestry. Since the mid-nineteenth century, evidence has been building that creatures anatomically and behaviorally identical to us have been on this planet for a very long time, far longer than the biblical 6,000 years. We could leave Darwin and evolution entirely out of the picture, and we would still be having a conversation about the historicity of Genesis 2 and 3. The same issues pertain to any OEC scenario. Most proponents of ID can’t duck this, either, even though they get to say “officially” that ID isn’t about the Bible. Because most ID proponents are not YECs, they accept the general validity of the methods used to date rocks and fossils, and so (by implication) this is their problem, too, whether or not it’s acknowledged.

To illustrate my point historically, let me introduce readers to George Frederick Wright (read more here and here). Ronald Numbers, the leading historian of American religion and science, wrote a clear, detailed article about this (see the reference below) that I strongly recommend to anyone who’s interest has been piqued. An influential Congregationalist clergyman and theologian, Wright was mentored by Harvard botanist Asa Gray, served briefly under Thomas C. Chamberlin on the U. S. Geological Survey, and even contributed articles on early humans and the ice age—his specialty—to scientific journals. During the 1870s, he worked closely with Gray to promote what is usually seen as a type of Theistic Evolution. By the early twentieth century, however, he appeared in some of his writings to have almost completely reversed his views on evolution. He even contributed an essay on “The Passing of Evolution” to the famous pamphlets, The Fundamentals, that later gave its name to that movement.

In other writings, however, Wright seemed to remain convinced of evolution, at one point saying that, “it is difficult to resist the conclusion that, so far as his physical organism is concerned, man is genetically connected with the highest order of the Mammalia.” Whatever he really thought about common ancestry—whether he was really a TE, an OEC, or an ID (one could make a good case for each)—the question of human antiquity dogged Wright for decades, as he sought ways to reconcile the genealogies in Genesis with accumulating evidence that humans have existed much longer than 6,000 years. Fortunately for Wright’s Christian faith, which probably hung in the balance, the famous Princeton theologian Benjamin Breckenridge Warfield, together with the conservative biblical scholar William Henry Green, managed to persuade Wright that the Genesis genealogies had plenty of wiggle room. Anyone wanting to see the crucial details should read Green’s paper on “Primeval Chronology” at this point. Note Warfield’s own conclusion (same URL): “There is no reason inherent in the nature of the Scriptural genealogies why a genealogy of ten recorded links, as each of those in Genesis v. and xi. is, may not represent an actual descent of a hundred or a thousand or ten thousand links.”

Can this really be true, without straining the whole idea of historicity? Davis Young’s skepticism seems appropriate here. How far back can we place Adam and Eve and still have contact with the biblical period? In my opinion, a clear and convincing picture of an historical Adam and Eve, reconciling the biblical picture with human antiquity, has not yet been produced, and I am doubtful that we will ever have one. Those who want more information about the possibilities and the difficulties are invited to consult the articles (cited below) by anthropologist James Hurd, evolutionary biologist David Wilcox, and anthropologist Dean Arnold. To the best of my knowledge, Hurd and Wilcox are TEs, while Arnold is an OEC. It’s up to you, my “students,” to consult these sources and place summaries and comments below. I’ve done enough already.

Looking Ahead

In about two weeks, I’ll conclude with a short history of Theistic Evolution. There’s plenty to think about in the interval. Please follow some of these links, borrow some of these books, and add your views to mine.

Citations

Dean Arnold, “How Do Scientific Views on Human Origins Relate to the Bible?” in Not Just Science, edited by Dorothy F. Chappell & E. David Cook (Zondervan, 2005), 129-40.

Robin Collins, “Evolution and Original Sin,” in Perspectives on an Evolving Creation, edited by Keith B. Miller (Eerdmans, 2003), 469-501.

James P. Hurd, “Hominids in the Garden?” in Perspectives on an Evolving Creation, 208-33.

Ronald L. Numbers, “George Frederick Wright: From Christian Darwinist to Fundamentalist,” Isis 79 (1988): 624–45.

David Wilcox, “Finding Adam: The Genetics of Human Origins,” in Perspectives on an Evolving Creation, 234-53.

In his essay for that series, Jeff Schloss addressed the question of whether animal death is a natural evil, but also noted that such theological considerations aside, death does not actually “drive evolution” in the way most people imagine—especially when they think of violence in the natural world. This more complicated sense of death’s role is partially the result of modern evolutionary science recognizing the importance of cooperation and inter-relation among species, rather than just direct competition. But just as important is the knowledge that evolution is significantly shaped not by the deaths of individual creatures, but by extinction, the loss of species over time. In this post, we explore some aspects of how extinction acts as both a destructive and creative force in evolutionary history, including the evolutionary history of mammals.

Sporadic extinction

Extinction is actually a common feature of life on earth when viewed over long (e.g. geological) timescales. By some estimates, over 99% of the species that have ever lived have gone extinct. One factor that promotes extinction is the fact that evolution does not produce species that are optimally adapted to their environment, but only better adapted than their local competitors. Invasive species testify to this fact: local (endemic) species are not always the best-adapted species for their own environment. Examples abound where species from other environments are actually better-suited to out-compete endemic species. Here in my own province, the invasive Himilayan blackberry (Rubis discolor) easily outcompetes many endemic species. If endemic species were optimally adapted to their environment, this would not be possible, as they would outcompete all exotic species. Instead, exotic species, by chance, might be better adapted to an ecosystem they did not evolve in. These exotics may be capable of eliminating endemic species altogether.

Such an extinction event (of a single species, or perhaps a handful of species) alters the environment of other remaining species in an ecosystem. This, in turn, may influence the ability of some of these remaining species to reproduce compared to other species. For example, the extinction of a competitor might allow a species to increase in population size. Conversely, the extinction of a species that provides a benefit (such as a pollinator) may reduce a species in number. As the ecosystem landscape shifts due to loss of species, new biological opportunities, or niches, might arise. These new niches are then available to support new species to fill them.

Extinction, en masse

One way to appreciate how extinction opens up new niches is to examine mass extinction events – geologically brief periods where large numbers of species go extinct at the same time. Over the history of life on our planet there have been several mass extinction events. The largest such event, at the end of the Permian (~250 million years ago) appears to have been caused, at least in part, by intense volcanic activity over several hundred thousand years. This activity likely shifted CO2 levels and eventually led to a “runaway” greenhouse effect that dramatically raised global temperatures and led to anoxic (i.e. oxygen-depleted) oceans, though the exact contributions of these varied factors remains an area of scientific debate. What appears certain is that during this period environmental changes were too rapid for most species to keep evolutionary pace with, and as a result over 90% of the world’s species alive at that time went extinct. Obviously this represents destruction of biodiversity on an unimaginable scale, and the destructive effects of this event are with us to this day.

Speciation, en masse

This destruction, however, is not the whole story. Following on from the Permian mass extinction, we observe a steady increase in new species. These are species previously unknown in the fossil record. In fact, this pattern (a “radiation” of new species following an extinction event) is the rule, not an exception – we see the same effect after every mass extinction in the fossil record. Extinction is a driving force for novelty.

Perhaps the most famous mass extinction event is the Cretaceous – Paleogene (KPg) extinction, and it too follows this standard pattern. This mass extinction took place 65 million years ago when an asteroid ~10 kilometers in diameter struck the Yucatan peninsula. (Note: this event was formerly known as the Cretaceous – Tertiary (K-T) extinction, but that terminology is in decline within the scientific community). This extinction event is famous since it is the one that eliminated the dinosaurs (with the exception of the ancestors of modern birds). As with the Permian extinction, the elimination of so many species shifted the evolutionary landscape for the remaining species, and the result was a burst of speciation that appears rapid when viewed in geological time. Significantly for our own species, following the KPg extinction event is a burst in mammalian speciation, as small mammals that survived the event diverge and fill niches left empty by the dinosaurs. Without this event, the trajectory of mammalian evolution would certainly look very different.

Clearing the deck, and re-filling the niches

One interesting fact to note is that biological features that make a species resistant to usual, sporadic extinction are not necessarily the same features that will be useful during a mass extinction event. While species are continually under selection at the local level, there is no mechanism for (pre) selection to survive a mass extinction. As such, only species that happen to have the right combination of traits will survive, and often spread widely after a mass extinction. These so-called “disaster species” are usually generalists, and will later be displaced by more specialized species as they arise. As such, where sporadic extinction allows for more gradual turnover in species, mass extinction events are major “resets” of evolution that can radically shift what constitutes “well adapted” in a geological eyeblink. For mammals at the KPg boundary, small body size and an omnivorous diet (including the ability to scavenge detritus) were the “winning” combination of traits that allowed them to survive where larger, more specialized animals (think Tyrannosaurus rex) could not. From this rather humble station, mammals would come to dominate the world’s ecosystems over the coming eons – including a lineage that would someday lead to our own species. Far from only a destructive force, extinction is a powerful mechanism to allow evolutionary innovation, and one that was of significant importance to us.

For further reading:

Meredith, R.W. et al (2011). Impacts of the Cretaceous Terrestrial Revolution and KPg Extinction on Mammal Diversification. Science 334; 521-524.

Fastovsky, D.E. (2005). The Extinction of the Dinosaurs in North America. GSA Today (15); 1052-5173.

Benton, M.J. and Twitchett, R.J. (2003). How to kill (almost) all life: the end-Permian extinction event. TRENDS in Ecology and Evolution (18); 358-365.

There are two opposite errors which need to be countered about the fossil record: 1) that it is so incomplete as to be of no value in interpreting patterns and trends in the history of life, and 2) that it is so good that we should expect a relatively complete record of the details of evolutionary transitions within all or most lineages.

What then is the quality of the fossil record? It can be confidently stated that only a very small fraction of the species that once lived on Earth have been preserved in the rock record and subsequently discovered and described by science.

There is an entire field of scientific research referred to as "taphonomy" -- literally, "the study of death." Taphonomic research includes investigating those processes active from the time of death of an organism until its final burial by sediment. These processes include decomposition, scavenging, mechanical destruction, transportation, and chemical dissolution and alteration. The ways in which the remains of organisms are subsequently mechanically and chemically altered after burial are also examined -- including the various processes of fossilization. Burial and "fossilization" of an organism's remains in no way guarantees its ultimate preservation as a fossil. Processes such as dissolution and recrystallization can remove all record of fossils from the rock. What we collect as fossils are thus the "lucky" organisms that have avoided the wide spectrum of destructive pre- and post-depositional processes arrayed against them.

Soft-bodied organisms, and organisms with non-mineralized skeletons have very little chance of preservation under most environmental conditions. Until the Cambrian nearly all organisms were soft-bodied, and even today the majority of species in marine communities are soft-bodied. The discovery of new soft-bodied fossil localities is always met with great enthusiasm. These localities typically turn up new species with unusual morphologies, and new higher taxa can be erected on the basis of a few specimens! Such localities are also erratically and widely spaced geographically and in geologic time.

Even those organisms with preservable hard parts are unlikely to be preserved under "normal" conditions. Studies of the fate of clam shells in shallow coastal waters reveal that shells are rapidly destroyed by scavenging, boring, chemical dissolution and breakage. Occasional burial during major storm events is one process that favors the incorporation of shells into the sedimentary record, and their ultimate preservation as fossils. Getting terrestrial vertebrate material into the fossil record is even more difficult. The terrestrial environment is a very destructive one: with decomposition and scavenging together with physical and chemical destruction by weathering.

The potential for fossil preservation varies dramatically from environment to environment. Preservation is enhanced under conditions that limit destructive physical and biological processes. Thus marine and fresh water environments with low oxygen levels, high salinities, or relatively high rates of sediment deposition favor preservation. Similarly, in some environments biochemical conditions can favor the early mineralization of skeletons and even soft tissues by a variety of compounds (eg. carbonate, silica, pyrite, and phosphate). The likelihood of preservation is thus highly variable. As a result, the fossil record is biased toward sampling the biota of certain types of environments, and against sampling the biota of others.

In addition to these preservational biases, the erosion, deformation and metamorphism of originally fossiliferous sedimentary rock have eliminated significant portions of the fossil record over geologic time. Furthermore, much of the fossil-bearing sedimentary record is hidden in the subsurface, or located in poorly accessible or little studied geographic areas. For these reasons, of those once-living species actually preserved in the fossil record, only a small portion have been discovered and described by science. However, there is also the promise of continued new and important discovery.

The forces arrayed against fossil preservation also guarantee that the earliest fossils known for a given animal group will always date to some time after that group first evolved. The fossil record always provides only minimum ages for the first appearance of organisms.

Because of the biases of the fossil record, the most abundant and geographically widespread species of hardpart-bearing organisms would tend to be best represented. Also, short-lived species that belonged to rapidly evolving lines of descent are less likely to be preserved than long-lived stable species. Because evolutionary change is probably most rapid within small isolated populations, a detailed species-by-species record of such evolutionary transitions is unlikely to be preserved. Furthermore, capturing such evolutionary events in the fossil record requires the fortuitous sampling of the particular geographic locality where the changes occurred.

Using the model of a branching tree of life, the expectation is for the preservation of isolated branches on an originally very bushy evolutionary tree. A few of these branches (lines of descent) would be fairly complete, while most are reconstructed with only very fragmentary evidence. As a result, the large-scale patterns of evolutionary history can generally be better discerned than the population-by-population or species-by-species transitions. Evolutionary trends over longer periods of time and across greater anatomical transitions can be followed by reconstructing the sequences in which anatomical features were acquired within an evolving branch of the tree of life.

Evolution: just a theory

One game that my (young) children like to play is a guessing game where both players select a character from among many choices, and by process of elimination, tries to guess the character the other has selected. Questions like “does your character have red hair? glasses?” etc., are used to narrow down the possibilities. Once you have guessed correctly which character your opponent has selected, you can perfectly predict the answer to every question thereafter (and a good many parents likely prolong the questioning to keep the hopes of victory alive for their children). When considered separately, the individual features of each character—glasses, brown hair, purple hat, and so on—mean almost nothing, since they could be features shared with other characters in the game. Only the convergence of multiple features is indicative of a good guess, and the accuracy of that guess is put to the test every time a new question is asked.

A good theory is something like this: an educated guess, based on and consistent with all past work on the topic to date. It allows you to predict how future tests should pan out. In the guessing game, there are limited options to choose from (so the analogy, like all analogies, eventually breaks down). In science, we don’t really know the true way things actually work. What we have are theories—broad explanatory frameworks supported by experimentation, that make sense of our current collection of facts—that we can use to make testable predictions about the natural world. All theories in science are provisional in that they are not complete descriptions of how the world actually works and are subject to future revision; but at the same time they are robust frameworks that can be used to predict how experiments should behave with almost boring regularity. So, far from the colloquial usage of “theory” as speculation, “just a theory” is high praise in science.

The current understanding of evolutionary theory in all its scope and diversity is far more complex than Darwin himself could have ever envisaged. (As a geneticist, I’ve often wished I could have a cup of tea with him to show him how far his theory has grown, especially given his confusion about how heredity worked.) Our understanding of how evolution works has grown by leaps and bounds since the 1850s. What is remarkable is just how much Darwin got “right” given his time and place. His main hypotheses—that species descend from ancestral forms through descent with modification, that and natural selection acting on heritable variation is a significant force in that process—remains the core of modern evolutionary theory. We’ve added a lot of detail since then (population genetics, kin selection, neutral evolution/genetic drift, symbiosis, horizontal gene transfer, molecular exaptation, and so on), but Darwin’s core ideas have produced a wealth of successful predictions. They were a very good “guess” that continues to pay rich scientific dividends.

Whale evolution: an example of converging lines of evidence

One of the things I personally find quite enjoyable about evolutionary theory is the counter-intuitiveness of some of the predictions it makes. One example that is a personal favorite, and one I often use to illustrate how evolution makes sense of converging lines of evidence, is cetacean (whale) evolution. Let’s set up the “problem” that evolutionary biology forces upon us:

• Modern cetaceans are mammals – they nourish their young in utero through a placenta, give birth to live young, and feed newborns with milk – all features of standard mammalian biology.
• Mammals are tetrapods – organisms with four limbs. Mammalian life shows up in the fossil record as an innovation within tetrapods, so mammals are “nested within the set” of tetrapod forms. Not all tetrapods are mammals (amphibians, for example) but all mammals are tetrapods.
• Tetrapods are by and large terrestrial creatures. Having four limbs for locomotion is a distinctly land-based adaptation.

The “problem”, of course, is that modern whales are emphatically not terrestrial, nor do they have four limbs – they have two front flippers and a tail, with no hind limbs in sight. Yet they are mammals, which forces evolution’s hand as it were. Evolution thus is dragged, under protest, to the prediction that modern whales, as mammals, are descended, with modification, from ancestral terrestrial, tetrapod ancestors. Instantly this prediction raises a host of uncomfortable questions: where did their hind limbs go? How did they acquire a blowhole on the top of their heads when other mammals have two nostrils on the front of their faces? How did they transition to giving birth in the water? What happened to the teeth of the baleen whales? What happened to the hair characteristic of mammals? and so on. In some ways, evolutionary thinking about whales creates more difficulties than it appears to solve.

And yet, these difficulties are the stuff of science. If indeed our “educated guess” of terrestrial, tetrapod ancestry for whales is correct, the evidence will show that these transitions, challenging though they may seem, did indeed occur on the road to becoming “truly cetacean”.

Going out on a limb

Anyone who has seen a modern whale skeleton in a museum and noted it carefully may have noticed that though whales lack hind limbs, they do have a bit of bone back there where the hind limbs ought to be. While this is suggestive of a vestigial characteristic (a feature in a modern organism that has a reduced role relative to the role the structure played in an ancestral species), it’s hardly a smoking gun for evolution. Still, it’s consistent with the idea.

When we look at the cetacean fossil record, we also see forms suggestive of a progressive loss of hind limb function and structure over time, as David Kerk and Darrel Falk have elegantly explained before. Again, if one were resistant to evolutionary explanations, it would be possible (if a bit strained) to interpret these creatures as having been created directly as we find them in the fossil record. The facts that we do not see these forms in the present day, and that they seem to blur the distinctions between terrestrial tetrapods and whales might make one a bit uncomfortable, however.

Recent work on cetacean embryogenesis (how whales and their relatives develop from fertilized eggs into fully-formed baby whales) has shed even more light on the issue for modern species, however. Dolphin embryos actually have four limbs early in their development, as well as a few facial hairs, just as any good mammal should have. The hind limbs and hairs are lost later in development, and work on the molecular signaling events that halt hind limb growth and cause the limb bud to regress into the body wall have now been worked out in some detail. Moreover, early in dolphin development the nostrils are distinct and on the front of the face, and only fuse into a blowhole and migrate to the top of the head later in development. Early dolphin embryogenesis is distinctly mammalian and uncannily tetrapod-like.

… and passing the test

Taken in isolation, these facts about whales are interesting trivia. Taken together, however, they begin to form a picture entirely consistent with the prediction that modern whales are derived from terrestrial ancestors. The true strength of evolution as a scientific theory for the origin of whales is this: not that we can prove it, (for no theory is ever proven in science due to its permanently provisional nature), nor that we have full access to every bit of data we would like (consider how fragmentary the fossil record is, for example), but rather that we haven’t been able to disprove it yet, despite our best efforts. Descent with modification remains a productive educated guess that grows stronger with each investigation.

In the next post in this series, we’ll explore some additional lines of evidence for cetacean evolution that further illustrate the predictive power of evolutionary theory.

For further reading

Evidences for Evolution, Part 2a: The Whale's Tale

Evidences for Evolution, Part 2b: The Whale's Tale
J. G. M. Thewissen, M. J. Cohn, L. S. Stevens, S. Bajpai, J. Heyning, and W. E. Horton, Jr. (2006). Developmental basis for hind-limb loss in dolphins and origin of the cetacean bodyplan. Proceedings of the National Academy of Sciences 103 (22), 8414–8418. available freely online.

In our last two BioLogos podcasts, we looked at the question of transitional fossils and the genetic evidence for evolution. In our final installment of this three part series, we move on to the question of speciation and macroevolution. A common challenge to evolutionary theory is that while life does indeed change over time (what is known as microevolution), no one has ever seen one species evolve into another species (macroevolution). For example, no one has seen a dog evolve into something other than a dog. Because speciation has never been observed, and because science is based on observation, evolution cannot be considered scientific.

In fact, examples of speciation have been observed by scientists. We must also remember that we are able to observe just a tiny window of the long history of life on Earth, and the fact that any speciation has been noted at all is impressive indeed.

Transcript

It’s pretty clear to most of us that life can change over time. For those who aren’t convinced, just take a quick trip to your local animal shelter. Each of the dog breeds there, from the Great Dane to the Chihuahua, descended from a single ancestral population. As you probably already know, that ancestral group was a wolf-like species. -How did these drastic changes take place? Well, basically, genetic variation within that original population was acted upon by selective forces. Now, just to be clear, the selection at work here wasn’t natural. It was the result of breeding done over hundreds of years. But the basic principle is the same. Genetic variation plus some sort of selection results in genetic change. This is evolution.

For the most part we are ok with accepting this. Yet many people still have a problem with the Theory of Evolution. Those suspicious of evolutionary Theory generally split evolution into two categories. Instead of arguing that evolution is completely impossible, they will say something like, “I know microevolution is real, but I just can’t accept macroevolution.”

Kent Hovind, an especially outspoken opponent of evolutionary theory, often makes this argument in his presentations:

“Maybe you’re talking about macroevolution. That’s where an animal changes into a different kind of animal. Nobody’s ever seen that. Nobody’s seen a dog produce a non-dog. I mean you may get a big dog or a little dog, I understand, but you’re going to get a dog, okay?” (source)

But what does this mean? What is the difference between micro and macroevolution anyway, and why is one of them ok while the other is condemned?

Well, like many terms used in the evolution debate, the definitions tend to differ depending on who you talk to. This can make rational discussion difficult. Most opponents of evolution, like Kent Hovind, say that macroevolution refers to one “type” or “kind” of organism evolving into another “kind”. Microevolution, they might say, is evolution within a “kind”. Evolution of one dog breed into another, they would say, is microevolution. Evolution of a “dog into a non-dog”, as Hovind puts it, would be “macroevolution.”’

One big problem with this argument is that “kind” is not clearly defined. It is a subjective term referring to organisms that seem similar to each other. Now, this is a definition that can easily be manipulated. And it doesn’t work very well when asking scientific questions. Because there is disagreement about what they actually mean, the terms micro and macroevolution aren’t often used in scientific literature. But when biologists do refer to “macroevolution”, most define it as “evolution above the species level”.

(Sources: http://ib.berkeley.edu/courses/ib200a/lect/ib200a_lect26_Lindberg_macroevolution.pdf, http://www.nescent.org/media/NABT/, http://evolution.berkeley.edu/evosite/evo101/VIADefinition.shtml, http://www.nhm.ac.uk/hosted_sites/paleonet/paleo21/mevolution.html)

In other words, at the smallest scale, macroevolution is the development of a new species. This definition is more useful because you can objectively determine whether two organisms are members the same species, but “kind” has no specific definition.

So what does “species” mean anyway? How is it different from “kind?” Well, the term species can be hard to define. Life is complex, and categorizing it into clear groups can be tricky. The currently accepted definition of species comes from what we call the “biological species concept.” Basically, the biological species concept says that a species is made of populations that actually or potentially interbreed in nature.

So, two populations that cannot mate to produce successful offspring are by definition separate species. Now, this definition doesn’t always work. For example, when you have a species that reproduces asexually, finding the boundaries between species can be a little tricky. But in most cases it does a pretty good job. It’s a good way to objectively determine where one species stops and another one begins.

The Biological Species Concept is especially useful when you have two species that look and act very similar. Eastern and Western Meadowlarks are a good example of this. They look almost exactly the same. But they cannot interbreed successfully. Therefore, they are separate species. This definition also helps when we study evolution. Where can we draw the line between microevolution and macroevolution? Well, it’s never easy, but having a working definition of this thing called a species helps out a lot. When enough genetic changes accumulate in a population, eventually it loses the ability to mate with others of its species. Then, by definition, it becomes a new species. In other words, macroevolution has occurred.

As we just discussed, many critics claim that macroevolution can never happen—one species can never cross over to become another one. This statement might sound valid, but a little bit of investigation shows that it is not well supported by evidence. For one thing, the only difference between micro and macroevolution is scope. When enough micro changes accumulate, a population will eventually lose its ability to interbreed with other members of its species. At this point, we say that macroevolution has occurred.

The same processes—random mutation and natural selection—cause both micro and macro evolution. There are no invisible boundaries that prevent organisms from evolving into new species. It just takes time. Usually, the amount time required for macroevolution to occur is significant—on the order of thousands or millions of years. That’s why you don’t normally see brand new forms of life appear every time you step out your front door. And that’s also why some people think that speciation never happens at all.

But sometimes macroevolution doesn’t take that much time. In fact, the evolution of new species sometimes happens so quickly that we can actually see it take place! Let’s look at a few recent examples.

Biologists Peter and Rosemary Grant had been studying finches since 1973. They lived on an island called Daphne Major in the Galapagos. It was here that they conducted their studies. When they first began their studies, only two species of Finch lived on Daphne Major: the medium ground finch and the cactus finch. But, in 1981, Peter and Rosemary noticed that an odd new finch had immigrated to the island. It was a hybrid, a mix between a cactus finch and a medium ground finch. It didn’t quite fit in with the other birds. The odd misfit had an extra large beak, an unusual hybrid genome, and a new kind of song. But somehow he was still able to find a mate. The female was also a bit of a misfit and had some hybrid chromosomes of her own. So their offspring were very different from the other birds on the island.

Rosemary and Peter continued to carefully watch the odd hybrid line. They wondered if the birds would become isolated from the other finch species on the island or if they would eventually re-assimilate. After four finch generations, a drought killed off many of the birds on Daphne Major. In fact, almost the entire hybrid line was exterminated. Only a brother and sister pair remained. The two family members mated with each other, producing offspring that were even more unique than their parent line. From that point on, as far as biologists Peter and Rosemary could tell, the odd population of finches mated only with each other. They were never seen to breed with the cactus finches or the medium ground finches on the island. The finches with the strange song had become a brand new species.

(Source: http://www.pnas.org/content/106/48/20141.full)

Another example of speciation, or macroevolution, also took place on an island—this time, on the beautiful Portuguese island of Madeira. According to history books, the Island of Madeira was colonized by the Portuguese about 600 years ago. The colonizers brought with them a few unassuming European House Mice, which they accidentally left on the island. It’s also possible that a group of Portuguese House Mice was dropped off later on.

Recently, Britton-Davidian, an evolutionary biologist at University Montpellier 2 in France, decided to collect samples of the Madeira mice and see how those original populations had changed over time. What she found was surprising. Rather than just one or two species of mouse, she found several. In only a few hundred years, the original populations of Mice had separated into six genetically unique species. The first mouse populations had 40 chromosomes altogether. But the new ones were quite different. Each new variety had its own unique combination of chromosomes, which ranged in number from 22 to 30.

What seems to have happened is that, over time, the mice spread out across the island and split into separate groups. Madeira is a rugged volcanic island with crags and cliffs. So it makes sense that this would have been easy to do. There were many isolated corners for the mice to occupy. Over time, random mutations occurred—some chromosomes became fused together.

Now, In order to reproduce successfully, both parents must have the same number of chromosomes. So when a population develops a chromosome fusion, suddenly that group cannot mate with the other members of its species. It becomes a brand new species. That’s exactly what happened on Madeira. And because of this phenomenon, 6 new species evolved from just 1 or 2 in an extremely short amount of time.

(Sources: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2009.04345.x/full, http://www.genomenewsnetwork.org/articles/04_00/island_mice.shtml, http://www.nature.com/hdy/journal/v99/n4/full/6801021a.html)

Another fascinating example of macroevolution was recently observed by researchers at Pennsylvania State University. This time, two species combined to make a single new one. In 1997, researchers at Penn State noticed a fruit maggot infestation on some recently introduced Asian Honeysuckle bushes. They decided to investigate the Honeysuckle fly population and determine how it was related to the other flies nearby. When they examined the honeysuckle fly’s genes, the researchers discovered something interesting. The fly appeared to be a hybrid of two native species—the blueberry fly and the snowberry fly.

But the honeysuckle fly’s genetic material was not an exact balance between that of the two parent species. The ratios of DNA varied from fly to fly. This showed the researchers that the honeysuckle flies had been breeding amongst themselves for many generations—probably at least 100. Also, they found that the Honeysuckle Flies were very unlikely to breed with any other species. They bred only on their host Honeysuckle plants. So they weren’t likely to mix with flies that lived on a different host.

According to Dr. Dietmar Schwarz, post-doctoral researcher in entomology, as far as the researchers can tell, “The new species is already reproductively isolated. They seem to be in a niche on the brushy honeysuckle where the parent species cannot compete."

(Source: http://www.psiee.psu.edu/news/2005_news/july_2005/hybrid_insects.asp)

While this kind of speciation—two species hybridizing to create a new one—seems odd, it is a significant mechanism of macroevolution. And it’s especially common in plants. In fact, a new species of weed recently arose this way in Great Britain. In 1991, Richard Abbot, a plant evolutionary biologist from St. Andrews University, noticed an unusual weed growing next to a car park in York. He discovered that the species, an unassuming scruffy weed, was a natural hybrid between the common groundsel and the Oxford ragwort, a plant that was introduced to Britain only 300 years ago. The York Groundsel lives in a different niche, or microenvironment, than either of its parent species. It is able to breed and reproduce, but only with other York Groundsel plants. It cannot successfully reproduce with any other species, including either of its parent plants. Thus, by definition, the York Groundsel is its own new species.

(Sources: http://www.nerc.ac.uk/publications/planetearth/2003/summer/sum03-evolution.pdf, http://www.nature.com/hdy/journal/v69/n5/abs/hdy1992147a.html)

So, as we have seen, macroevolution is an established process. Usually it takes thousands of years to occur, but sometimes we get lucky and catch it in the act. When Kent Hovind said that, “no one has ever seen a dog produce a non-dog” he was technically quite correct. But this statement infers that macroevolution means a drastic and obvious change from one type of organism into another. Those who think this way believe that macroevolution is something like two dogs breeding to suddenly produce a cat, or two guinea pigs mating to produce a mouse.

But this is not how evolution works at all. Over millions of years, a dog-like animal may indeed evolve into a something that looks completely unlike a dog. However, this is not something that we would expect to be able to observe. It just takes too much time. To put the scale of evolution into perspective, consider this. If the average lifespan of a United Stated citizen, 78 years, were a single minute, then single-celled life has been around for nearly 100 years. On this scale, all we get to see is one minute. And even in that time frame we sometimes see new species forming. God’s time is not our time and we tend to forget this. What we do expect to observe is a very slow step-by-step accumulation of tiny genetic changes that eventually result in speciation. And indeed, as we discussed today, this is exactly the sort of evidence revealed in nature.

So, macroevolution is not a “myth” by any means. It is supported by a vast amount of evidence. That evidence includes the fossil record and genetics, as discussed in previous BioLogos podcasts, and, when we get lucky, direct observation of speciation. God, being who God is, could conceivably have created species out of thin air in a single instant. But what if instead if God created and sustained the process by which new species are created? Does that make him less powerful or less "god-like"? Is it somehow more God’s process if it happened in an instant, than it is if it happened over a long period of time? Presumably even if it happened in an instant, it would still happen by some sort of process—only faster.

God’s time is not our time, and perhaps it’s a good idea for all of us to simply stand back in amazement while God does God’s work in God’s time through God’s process.

I’d like to suggest that this argument is in significant ways misplaced. The participants in this debate all seem to agree that what makes us “human” can be defined by genes and population studies. There is a pressing need for them to conform theology to population genetics, or to conform population genetics to theology, because the story of our genes is implicitly equated with the story of what it means to be “human.” The hypothesis that there was a “first human” – a capital-A “Adam” – can be tested in our genes.

But “genes” do not make us “human.” What makes us “human” is the irreducible phenomena of all of our material and immaterial being as persons.

Nothing we observe in the universe is flat. By “flat” I mean having only one aspect or “layer.” Consider, for example, an apple. What is it? Is it the fruit of an apple tree? The seed-carrier – the potentiality – of new apple trees? Beautiful and delicious? Skin, flesh, and core? Water and organic molecules? Caloric energy and roughage? Hydrogen, oxygen, and carbon? Physical laws? All of these things comprise some of what we mean by “apple,” but none of them are what an “apple” is. The reality that is “apple” cannot be reduced to any one of its aspects or layers.

It is possible to think of these aspects or layers hierarchically, with “higher” layers that emerge from “lower” ones. Physical laws emerge from quantum probabilities; molecules emerge from physical laws; seeds, skin, flesh and core emerge from complex arrangements of molecules; beauty and delight emerge from the connection of skin, flesh and core to human sense perception;¹ “apple” emerges from all of this (and more) combined with the human cultural experience of this thing we call “apple.”

Notice that some “layers” can impinge or “supervene” on lower ones – for example, human sense perception and cultural experience do something to this thing confronting the subject in order for it to become “apple.” But notice also that “apple” is not merely a cultural construction. The word or signifier “apple,” of course, could be arbitrary, but there is an objective reality to the thing signified. The layer of human sense perception and cultural experience supervenes upon, but does not create, the lower-order reality from which it emerges.

Sociologist Christian Smith draws these strands together in a critical realist framework in his excellent book What Is a Person?: Rethinking Humanity, Social Life, and the Moral Good from the Person Up. In a critically realist approach to culture and human personhood, Smith suggests, “[h]uman beings do have an identifiable nature that is rooted in the natural world, although the character of human nature is such that it gives rise to capacities to construct variable meanings and identities….” Culture is a social construction, but it is not merely a social construction. Human beings are social, but they are not subsumed by the social. The reality we inhabit is “stratified”: it includes both the reality of individual conscious human agents and the reality of the social structures that emerge from the cultures created by those agents. These “personal” and “cultural” layers of the world interact with each other dynamically, each continually informing and changing the other.

Smith’s approach is helpful, but perhaps it does not go far enough. For Smith, as for critical realists in general, the phenomena of human culture remain subject to some degree of granular disaggregation, at least analytically. A phenomenological approach suggests that no “thing” can be broken into components and still comprise that “thing” – the genes that encode for apple trees are not apple seeds, apple seeds are not apple trees, and apple trees are not apples. The critical realist framework of stratification, emergence, and supervenience functions as a very useful heuristic device, but to describe what an apple is, we must approach the phenomenon of “apple” in its fullness. To know whether something falls into the kind “apple,” we must hold an ideal of everything an apple is, and compare the subject to the ideal.

And because of the transcendence of the ideal concept of “apple,” we can begin to speak of the relative excellence of particular instantiations of apples. What is an “excellent” apple? What distinguishes the excellent apple from a poor one? We can only ask such questions if “apple” means something more than the particular physical specimen in hand, whether firm, sweet and tart, or bruised and sour.

The same is true of human “persons.” We can say almost nothing about a “person” merely by observing genes, because genes are not “persons.” Populations genetics studies can provide models of the dispersion of genes through groups of biological entities, but they can tell us nothing whatsoever about when the first “human person” emerged. Indeed, for population genetics qua population genetics, there simply are no “persons” – for this is a science of the movement of genes, not a philosophical, sociological, or theological description of “persons.”

So what of “Adam?” It is often suggested that in Romans 5:12 Adam is a type of Christ. But, in fact, in Paul’s thought, as well as for the early Church Fathers, Christ is the type, the typos, a notion derived from the “stamp” or “seal” on an official document. There is a hint in Romans 5 of a truth that would only become clarified later in Christian theology – that the pre-incarnate Christ, the second person of the Trinity, always was. Whereas Arius declared that “there was a time when he [Christ] was not,” Nicea established the orthodox Christology of Christ’s eternal sonship. Thus Christ is and was the Redeemer, the one for whom creation was made and in whose death and resurrection creation always finds its fulfillment. Adam’s failure was that he went against type – he did not conform to Christ but rather tried to become something else, and thereby the true nature of humanity was broken.

Is the typos of Christ reducible to a set of genes? Surely not. It resides not in genes or in any other created thing but rather in the Triune life of God Himself. We might speak, in a roughly analogical way, of ideas we hold in our minds – say, the idea of a perfect Bordeaux, ruby-red, silky, smoky, plummy, luxurious. We could labor to instantiate that idea, combining genes and terroir and water and light and care, and perhaps we might achieve it, to the point where upon taking a sip we exclaim, “this – this – is Bordeaux. Nothing else is worthy of that name.”

This is what God said of Adam, when he gave him breath and a name. It is not something that God said of any other creature, even apparently some creatures that a modern population geneticist or paleoanthropologist might designate as ancestrally human based on genes or bones. Yet that Adam, and each of us in that Adam, fail to participate fully and unreservedly in the true nature of the true human, the nature of Christ. And so Pontius Pilot, an unwitting prophet, said of Christ: “behold, the man” (John 19:5, KJV). And so also Paul invites us to see: the sinful man, the broken seal, the first created Adam; and the true type, the seal of humanity’s future, the perfect Adam, the Christ. None of this is about the definitions and categories of modern science, as helpful and important as they may be for the progress of scientific thought. It is, rather, about the fullness of what it means to be human.

Notes

1. Human sense perception, of course, is an emergent property of an even more complex set of relations that give rise to the human “person.”

The song entitled “The Fall” by Gungor is from the artists’ latest album Ghosts Upon the Earth. The lyrics begin by painting a picture of the Fall as something in which each person has participated as indicated by the assertion that “the fruit (of the Fall of man) is seen in every eye and every hand.” After reflecting on the words, consider the discussion questions below.

“The Fall” by Gungor

The Fall, the Fall, Oh God, the Fall of man,
The fruit is found in every eye and every hand,
Nothing, there is nothing yet in truest form,
We walk like ghosts upon the Earth,
The ground it groans.

How long? How long will you wait?
How long? How long till you save us all, save us all?

Turn your face to me; turn your face to me.
Turn your face to me; turn your face to me.

The light, the light, the morning light is gone,
And all that is left is fragile breath and failing lungs.
The night, the night, the guiding night has come,
Uniting lover with his bride more precious than the dawn.

How long? How long must we wait?

Turn your face to me; turn your face to me.
Turn your face to me; turn your face to me.

Questions

1. By focusing only on the Fall as a historical event, have we consciously or unconsciously simplified it—almost removing ourselves from the story?

2. Besides Genesis 3, what other Scripture has inspired the opening lines of this song? Does the feeling evoked by these opening lines personalize that passage for you?

3. Have you ever felt: “the light, the light, the morning light is gone?” Have you experienced night as “guiding?” Who is the lover? What Scripture informs these lines?

4. Have you ever asked, “How long? How long?” Have you heard the answer, “Turn your face to me. Turn your face to me?”

5. Do you agree that the story of Adam and Eve is your story, except for one important difference? What is that difference for you?

Michael Gungor has also served as a pastor at the Bloom Church in Denver, Colorado. Below we post an excerpt from a sermon he has given on his own personal journey and his views about science and Scripture.

(To hear the entire sermon go to this link and scroll to sermon of March 8, 2009—“What Can We Learn About Jesus from Science?”)

The beauty of the scientific process is its inherent scepticism. (See "What Scientists Do" by Steven Benner). If there is only one way of reaching a conclusion, the scientific process requires the scientist to remain highly sceptical. The only conclusions in science which are widely accepted are those which are supported by multiple, reinforcing lines of evidence – “all roads must lead to Rome”. If there is even one scientific trajectory that seems to clearly lead off to Peoria instead of Rome (to use a recent analogy of Francisco Ayala), the scientific process demands that the scientist find out why. The scientist who does not retain an attitude of scepticism when there is only a single line of evidence, and particularly one who ignores other, conflicting lines of evidence, is on a stubborn trajectory of his own—a trajectory to failure. If the only reason for following the directions which “lead away from Rome” is a particular view of Scripture, then it is important to consider the possibility of human error. Biblical hermeneutics, after all, is a human enterprise just as science itself is. For example, John MacArthur in his current series on Genesis is human and is interpreting Genesis in his way just like the rest of us. He, wonderful pastor and shepherd that he is, interprets Scripture too. There is good reason to be quite certain that the interpretation he subscribes to is mistaken.

As Christians, we are called to follow Jesus. In so doing, Jesus said we are to love the Lord our God with all our heart, soul and mind—not just our heart and soul. Indeed if we close our mind, we are actually disobeying what Jesus said was the greatest commandment of all. So let’s not be shy about using those minds. Are there multiple independent ways of keeping track of time since the creation of the earth? If so, do each of those ways point to the same conclusion?

The best known method of calculating the age of material on earth depends on the well-established fact that certain elements in the earth’s crust are unstable and decay at a fixed rate that can be measured. (For an introduction to this topic see this BioLogos FAQ.) This instability functions sort of like a set of clocks that have been ticking through the eons of time. Indeed there are many types of unstable elements; there are many ticking clocks. Each of the various clocks tick at a different rate. The rate of each can be calibrated, and, with an amazing degree of consistency, all “clocks” point back to the same starting point: an ancient earth with rocks that are hundreds of millions and even billions of years old. This “ticking clock” technique is known as radiometric dating.^1,2

There are other totally independent ways of estimating the age of material on earth. To appreciate how these work, perhaps we should start with shorter spans of time, which for human beings are much more readily comprehensible. Some of the fondest boyhood memories of one of us (DK) come from visits to the majestic California redwood forests. He especially remembers an exhibit of a section from a giant tree which showed the pattern of growth rings within it. It turns out that these rings accumulate in response to seasonal differences in rainfall and temperature, which in turn produces differences in growth rate. Fastened within this huge slab of wood was a series of tags, proceeding from the surface inward, demonstrating the dates of major historical events: the landing of the Pilgrims on Plymouth Rock; Columbus’ discovery of the New World; the Norman conquest of England, and so forth. It was possible to see in the yearly growth rings a history of what seemed then to be the very distant past!³

Growth layering processes are not restricted to trees. Many species of marine invertebrates accumulate calcium carbonate from their watery environment and incorporate it into some form of shell. Examples would be clams and corals. In fact, for these species, the variation in shell deposition occurs on a both a daily and a yearly basis, so an even finer counting of time periods is possible.⁴

Just as it is possible to count the rings in trees and correlate their age to known historical events in the past, it is also possible to count the banding patterns preserved in the fossils of marine organisms, and use this as a method to estimate their ages. Let’s see how it works.

Astronomical data, developed and analyzed over the past couple of centuries, has revealed that the rotation of the earth is gradually slowing down. This is due to the friction created daily by the moving tides on the earth’s surface, produced by the gravitational pull of the moon and sun. Furthermore, as the earth slows down slightly, some rotational energy is transferred to the moon, which alters its orbit slightly (its orbit is moving slowly away from the earth). The data leading to these conclusions range from analysis of ancient solar eclipses (whose dating allows the precise position of the earth, sun and moon to be determined) to bouncing laser beams off mirrors placed on the surface of the moon by the Apollo astronauts. For our purposes, what will be important is the slowing of the earth’s rotation. This predicts that the length of each day has been slowly increasing since the formation of the earth/moon system. The average increase in the day length is estimated at 2.3 milliseconds (.0023 seconds) per century.^5,6 Hence as we examine events in the past, day length was shorter, by an amount that can be calculated. Ten thousand years ago, a day would have been .23 seconds shorter than it is today. If direct experimental estimates of day length can be obtained, they allow an estimate of the age of the material.

One way that such experimental estimates of day length can be obtained is through the periodic growth rings deposited in the shells of marine invertebrate organisms. Take for example a clam living in an intertidal environment. If the tide is in and the shell is open, it can readily absorb oxygen from water, use aerobic metabolism, and incorporate calcium carbonate into its shells. When the tide is out and the shells are closed, however, little oxygen can be absorbed, anaerobic metabolism is used, shell decalcification occurs, and organic rich material accumulates in the shell. This alternating pattern of shell deposition occurs on a daily basis, and is clearly visible in both shells from living and fossil clam species by microscopic examination. Furthermore, shells contain an identifiable mark resulting from the first freezing day of winter, and from the first really hot day of summer. Hence a yearly growth interval can be readily determined.⁷

When such data are analyzed for a number of fossil species, it is clear that the number of days these organisms experienced each year was higher than today. Given that, we have another clock - a totally independent way of measuring the age of certain fossils. So how well do clocks based upon radiometric dating agree with those based on measuring rings in certain sea shells?

As already mentioned, organisms living 10,000 years ago would have experienced shorter days, but they would only have been shorter by 0.2 seconds. Organisms living 1 million years ago would have experienced a day length that was 20 seconds shorter. If the earth really is very, very old, organisms living 465 million years ago, for example, would have experienced approximately 416 days per year, each day being about 21 hours long.⁷ Amazingly, shelled fossils in formations dated by radiometric clocks to be about 465 million years old show, by their banding patterns, that the days really were three hours shorter. In fact the two sets of clocks agree within 1 percent!

Another way such estimates of ancient day length can be derived is to look at the periodic patterns formed in fine silts in ancient river estuaries. The daily tides produce shifts in the mud, leaving a fine layering pattern, which is recorded in rock as these sediments transform into materials such as sandstone (such deposits are called “rhythmites”). Other shifts in the mud are produced over longer time intervals, including seasonal and yearly shifts. By counting the number of daily depositional layers per year, in a similar fashion to work with marine organism shells cited above, an estimate of ancient day length can be derived. One advantage of the rhythmite analysis method is that it can be applied to more ancient materials, in eras of the earth’s history when organisms suitable for shell analysis were scarce or non-existent. For example, radiometric analysis of certain rock formations in South Australia dated them at 620 million years of age. On this basis one would predict that the day/night cycles should have been about 20 hours long in these formations. Actual measurements of day length from the preserved mud banding patterns, although off from the expected by ten percent (estimated day length is 22 hours) is again consistent with the formation being hundreds of millions of years old just as the radiometric dating has predicted.⁸

In conclusion, there is data derived from three independent sources: the decay of radioisotopes, the growth patterns recorded in fossilized shells of marine organisms, and rocks containing tidal depositional material from river estuaries, which all agree on an ancient age for the earth. Furthermore, by a totally independent method it is also possible to measure the age of the universe as a whole and again it is billions, not thousands of years.

All of the roads in God’s book of Nature “lead to Rome” (i.e an ancient earth) - it is only mistaken human interpretation of Scripture that causes some of our precious brothers and sisters in Christ to end up in Peoria.

The next blog in this series can be found here.

Editor's Note: Dr. Kerk offers a further discussion of the age of the earth in the comment section of this post, beginning here. Dr. Kerk has also included the following graph:

References

1: Elementary principles of radiometric dating are discussed by Richard Dawkins. Dawkins, R. 2009. The Greatest Show on Earth: The Evidence for Evolution. Free Press, New York Pgs. 91-98.

2: Wiens, R.C. 2002. Radiometric Dating: A Christian Perspective. This is a more detailed but still highly readable account of radiometric dating, written by a well-qualified physicist who is also a professing Christian. It can be obtained from the web site of the American Scientific Affiliation: http://www.asa3.org/ASA/resources/Wiens.html

3: Tree ring dating (“dendrochronology”) is discussed by Dawkins, pgs. 88-91.

4: Dating using coral skeletal deposition is discussed by Jerry Coyne: Coyne, J.A. 2009. Why Evolution is True. Viking Penguin, New York. Pgs. 24-25.

5: “Tidal Acceleration”, Wikipedia: http://en.wikipedia.org/wiki/Tidal_acceleration

6: Stephenson, F.R. 2003. Historical Eclipses and Earth’s Rotation. Astronomy and Geophysics 44:2.22-2.27.

7: Zhenyu, Z., Yaoqi Z., Guosheng J. 2007. The periodic growth increments of biological shells and the orbital parameters of Earth-Moon system. Environmental Geology 51: 1271–1277.

8: Williams, G.E. 2000. Geological constraints on the Precambrian history of Earth's rotation and the Moon's orbit. Reviews of Geophysics 38(1):37-59.

Misconceptions about Evolution and the Nature of Science

“Evolution is not science because it is not observable or testable.”

This misconception encompasses two incorrect ideas: (1) that all science depends on controlled laboratory experiments, and (2) that evolution cannot be studied with such experiments. First, many scientific investigations do not involve experiments or direct observation. Astronomers cannot hold stars in their hands and geologists cannot go back in time, but both scientists can learn a great deal about the universe through observation and comparison. In the same way, evolutionary biologists can test their ideas about the history of life on Earth by making observations in the real world. Second, though we can't run an experiment that will tell us how the dinosaur lineage radiated, we can study many aspects of evolution with controlled experiments in a laboratory setting. In organisms with short generation times (e.g., bacteria or fruit flies), we can actually observe evolution in action over the course of an experiment. And in some cases, biologists have observed evolution occurring in the wild.

"Evolution is 'just' a theory."

This misconception stems from a mix-up between casual and scientific use of the word theory. In everyday language, theory is often used to mean a hunch with little evidential support. Scientific theories, on the other hand, are broad explanations for a wide range of phenomena. In order to be accepted by the scientific community, a theory must be strongly supported by many different lines of evidence. Evolution is a well-supported and broadly accepted scientific theory; it is not ‘just' a hunch.

For more, see the question "What is evolution?"

"Evolutionary theory is invalid because it is incomplete and cannot give a total explanation for the biodiversity we see around us."

This misconception stems from a misunderstanding of the nature of scientific theories. All scientific theories (from evolutionary theory to atomic theory) are works in progress. As new evidence is discovered and new ideas are developed, our understanding of how the world works changes and so too do scientific theories. While we don't know everything there is to know about evolution (or any other scientific discipline, for that matter), we do know a great deal about the history of life, the pattern of lineage-splitting through time, and the mechanisms that have caused these changes. And more will be learned in the future. Evolutionary theory, like any scientific theory, does not yet explain everything we observe in the natural world. However, evolutionary theory does help us understand a wide range of observations (from the rise of antibiotic-resistant bacteria to the physical match between pollinators and their preferred flowers), does make accurate predictions in new situations (e.g., that treating AIDS patients with a cocktail of medications should slow the evolution of the virus), and has proven itself time and time again in thousands of experiments and observational studies.

For more, see the questions "How can evolution account for the complexity of life on earth today?" and "How can evolution account for the complexity of life on earth today?"

"Gaps in the fossil record disprove evolution."

While it's true that there are gaps in the fossil record, this does not constitute evidence against evolutionary theory. Scientists evaluate hypotheses and theories by figuring out what we would expect to observe if a particular idea were true and then seeing if those expectations are borne out. If evolutionary theory were true, then we'd expect there to have been transitional forms connecting ancient species with their ancestors and descendents. This expectation has been borne out. Paleontologists have found many fossils with transitional features, and new fossils are discovered all the time. However, if evolutionary theory were true, we would not expect all of these forms to be preserved in the fossil record. Many organisms don't have any body parts that fossilize well, the environmental conditions for forming good fossils are rare, and of course, we've only discovered a small percentage of the fossils that might be preserved somewhere on Earth. So scientists expect that for many evolutionary transitions, there will be gaps in the fossil record.

For more see out question "What does the fossil record show?"

Misconceptions about the Acceptance and Implications of Evolution

“Evolution is a theory in crisis and is collapsing as scientists lose confidence in it.”

Evolutionary theory is not in crisis; scientists accept evolution as the best explanation for life's diversity because of the multiple lines of evidence supporting it, its broad power to explain biological phenomena, and its ability to make accurate predictions in a wide variety of situations. The vast majority of scientists do not debate whether evolution took place, but they do debate many details of how evolution occurred and occurs in different circumstances. Antievolutionists may hear the debates about how evolution occurs and misinterpret them as debates about whether evolution occurs. Evolution is sound science and is treated accordingly by scientists and scholars worldwide.

For more see the questions "Does thermodynamics disprove evolution?", "How can evolution account for the complexity of life on earth today?" and "How can evolution account for the complexity of life on earth today?"

"Evolution supports the idea that 'might makes right' and rationalizes the oppression of some people by others."

In the nineteenth and early twentieth centuries, a philosophy called Social Darwinism arose from a misguided effort to apply lessons from biological evolution to society. Social Darwinism suggests that society should allow the weak and less fit to fail and die and that this is good policy and morally right. Supposedly, evolution by natural selection provided support for these ideas. Pre-existing prejudices were rationalized by the notion that colonized nations, poor people, or disadvantaged minorities must have deserved their situations because they were "less fit" than those who were better off. In this case, science was misapplied to promote a social and political agenda. While Social Darwinism as a political and social orientation has been broadly rejected, the scientific idea of biological evolution has stood the test of time.

"Evolution and religion are incompatible."

Because of some individuals and groups stridently declaring their beliefs, it's easy to get the impression that science (which includes evolution) and religion are at war; however, the idea that one always has to choose between science and religion is incorrect. People of many different faiths and levels of scientific expertise see no contradiction at all between science and religion.

In fact, science and religion can have a constructive relationship. The majority of scientists during the emergence of modern science in medieval Europe, for example, were devout or conventionally religious. Religious belief, then, can function as a framework within which scientific progress flourishes. Religious belief can also be influenced by science. In the Galileo Affair, scientific evidence of a heliocentric universe caused the church to revisit its interpretation of a part of Scripture.

Oddly enough, some people argue that God’s existence is actually a scientific claim and should be tested like any other. However, God’s existence is not something that can be tested by the scientific method in the same way the existence of postulated new elementary particles are tested in supercolliders. Because science provides knowledge about the natural world, no amount of testing or theorizing could prove or disprove the existence of a supernatural creator. Rather than an empirical claim about nature or its laws, the claim that God exists is a metaphysical one, a statement about what there is, whether it be natural or supernatural.

For more see the questions "What is the proper relationship between science and religion?", "Can scientific and scriptural truth be reconciled?", "What were the initial Christian responses to Darwin?", and "What role could God have in evolution?"

Misconceptions about Evolutionary Theory and Process

"Evolution is a theory about the origin of life."

Evolutionary theory does encompass ideas and evidence regarding life's origins (e.g., whether or not it happened near a deep-sea vent, which organic molecules came first, etc.), but this is not the central focus of evolutionary theory. Most of evolutionary biology deals with how life changed after its origin. Regardless of how life started, afterwards it branched and diversified, and most studies of evolution are focused on those processes.

For more, see our questions on "What is Evolution?" and "Isn't the Origin of Life Highly Improbable?".

"Evolution is like a climb up a ladder of progress; organisms are always getting better."

One important mechanism of evolution, natural selection, does result in the evolution of improved abilities to survive and reproduce; however, this does not mean that evolution is progressive — for several reasons. First, natural selection does not produce organisms perfectly suited to their environments. It often allows the survival of individuals with a range of traits — individuals that are "good enough" to survive. Hence, evolutionary change is not always necessary for species to persist. Many taxa (like some mosses, fungi, sharks, opossums, and crayfish) have changed little physically over great expanses of time. Second, there are other mechanisms of evolution that don't cause adaptive change. Mutation, migration and genetic drift may cause populations to evolve in ways that are actually harmful overall or make them less suitable for their environments. For example, the Afrikaner population of South Africa has an unusually high frequency of the gene responsible for Huntington's disease because the gene version drifted to high frequency as the population grew from a small starting population. Finally, the whole idea of "progress" doesn't make sense when it comes to evolution. Climates change, rivers shift course, new competitors invade — and an organism with traits that are beneficial in one situation may be poorly equipped for survival when the environment changes. And even if we focus on a single environment and habitat, the idea of how to measure "progress" is skewed by the perspective of the observer. From a plant's perspective, the best measure of progress might be photosynthetic ability; from a spider's it might be the efficiency of a venom delivery system; from a human's, cognitive ability. It is tempting to see evolution as a grand progressive ladder with Homo sapiens emerging at the top. But evolution produces a tree, not a ladder — and we are just one of many twigs on the tree.

For more, see our questions "What is Evolution?" and "Did Evolution Have to Result in Human Beings?".

"Evolution means that life changed 'by chance.'"

Chance and randomness do factor into evolution and the history of life in many different ways; however, some important mechanisms of evolution are non-random and these make the overall process non-random. For example, consider the process of natural selection, which results in adaptations — features of organisms that appear to suit the environment in which the organisms live (e.g., the fit between a flower and its pollinator, the coordinated response of the immune system to pathogens, and the ability of bats to echolocate). Such amazing adaptations clearly did not come about "by chance." They evolved via a combination of random and non-random processes. The process of mutation, which generates genetic variation, is random, but selection is non-random. Selection favored variants that were better able to survive and reproduce (e.g., to be pollinated, to fend off pathogens, or to navigate in the dark). Over many generations of random mutation and non-random selection, complex adaptations evolved. To say that evolution happens "by chance" ignores half of the picture.

For more see our questions on "What is Evolution?" and "How do randomness and chance align with belief in God’s sovereignty and purpose?".

“Humans are not currently evolving”

Humans are now able to modify our environments with technology. We have invented medical treatments, agricultural practices, and economic structures that significantly alter the challenges to reproduction and survival faced by modern humans. So, for example, because we can now treat diabetes with insulin, the gene versions that contribute to juvenile diabetes are no longer strongly selected against in developed countries. Some have argued that such technological advances mean that we've opted out of the evolutionary game and set ourselves beyond the reach of natural selection — essentially, that we've stopped evolving. However, this is not the case. Humans still face challenges to survival and reproduction, just not the same ones that we did 20,000 years ago. The direction, but not the fact of our evolution has changed. For example, modern humans living in densely populated areas face greater risks of epidemic diseases than did our hunter-gatherer ancestors (who did not come into close contact with so many people on a daily basis) — and this situation favors the spread of gene versions that protect against these diseases.

For more see our question "Did evolution have to result in human beings?".

"Species are distinct natural entities, with a clear definition, that can be easily recognized by anyone."

Many of us are familiar with the biological species concept, which defines a species as a group of individuals that actually or potentially interbreed in nature. That definition of a species might seem cut and dried — and for many organisms (e.g., mammals), it works well — but in many other cases, this definition is difficult to apply. For example, many bacteria reproduce mainly asexually. How can the biological species concept be applied to them? Many plants and some animals form hybrids in nature, even if they largely mate within their own groups. Should groups that occasionally hybridize in selected areas be considered the same species or separate species? The concept of a species is a fuzzy one because humans invented the concept to help get a grasp on the diversity of the natural world. It is difficult to apply because the term species reflects our attempts to give discrete names to different parts of the tree of life — which is not discrete at all, but a continuous web of life, connected from its roots to its leaves.

Misconceptions about Natural Selection and Adaptation

“Natural selection involves organisms trying to adapt”.

Natural selection leads to the adaptation of species over time, but the process does not involve effort, trying, or wanting. Natural selection naturally results from genetic variation in a population and the fact that some of those variants may be able to leave more offspring in the next generation than other variants. That genetic variation is generated by random mutation — a process that is unaffected by what organisms in the population want or what they are "trying" to do. Either an individual has genes that are good enough to survive and reproduce, or it does not; it can't get the right genes by "trying." For example bacteria do not evolve resistance to our antibiotics because they "try" so hard. Instead, resistance evolves because random mutation happens to generate some individuals that are better able to survive the antibiotic, and these individuals can reproduce more than other, leaving behind more resistant bacteria.

“The fittest organisms in a population are those that are strongest, healthiest, fastest, and/or largest.”

In evolutionary terms, fitness has a very different meaning than the everyday meaning of the word. An organism's evolutionary fitness does not indicate its health, but rather its ability to get its genes into the next generation. The more fertile offspring an organism leaves in the next generation, the fitter it is. This doesn't always correlate with strength, speed, or size. For example, a puny male bird with bright tail feathers might leave behind more offspring than a stronger, duller male, and a spindly plant with big seed pods may leave behind more offspring than a larger specimen — meaning that the puny bird and the spindly plant have higher evolutionary fitness than their stronger, larger counterparts.

“Natural selection produces organisms perfectly suited to their environments.”

Natural selection is not all-powerful. There are many reasons that natural selection cannot produce "perfectly-engineered" traits. For example, living things are made up of traits resulting from a complicated set of trade-offs — changing one feature for the better may mean changing another for the worse (e.g., a bird with the "perfect" tail plumage to attract mates maybe be particularly vulnerable to predators because of its long tail). And of course, because organisms have arisen through complex evolutionary histories (not a design process), their future evolution is often constrained by traits they have already evolved. For example, even if it were advantageous for an insect to grow in some way other than molting, this switch simply could not happen because molting is embedded in the genetic makeup of insects at many levels.

Today's video is courtesy of filmmaker Ryan Pettey, director/editor of Satellite Pictures.

Video transcript

I think there are sometimes a couple of biblical images we struggle to lay hold of. In the New Testament we find when we talk about life, we have the idea of living or ‘bios’. In other words, we talk about how we are alive. But Jesus talks about the fact of “coming to life “ when we know him. That doesn’t suddenly mean that our heart starts beating. It means that there is this whole side to us which was dead… which wasn’t alive and is now… that has actually sprung to life. And we run into complications maybe if we reduce all of these things into exactly the same categories. Now you can have the same issues with ‘death’ too. That word is used in many ways, and different words are used to try and signify various different things.

Now what is interesting is that if you go back into the Genesis account, it says “now do not eat this [apple] or you will surely die”. There is a whole chain of events that happens when Adam and Eve decide they want to walk away from God. The first thing that happens is that they cover themselves up. There’s like a psychological alienation that comes. They are no longer happy with the way they are. The next thing that happens is God steps into the garden, they run and hide. There is spiritual alienation. The voice that was once welcoming where they went, they now find themselves cut off from that. Then there is a social alienation that comes as a result of turning away from God. They start blaming each other. There is a vocational alienation that comes as a result of, of course, judgment. That which was meant to be home for them, all work become labor, and we could keep going.

So when we talk about “death” the picture, to me, seems to be much bigger, much fuller. I can’t think of a more comprehensive view of possibly what it could mean. And so I think we need to again break away from a straight forward, in fact, mechanistic understanding. In no way do I think that impoverishes either or understanding of the gospel or of the cross. As a matter of fact, it enhances it. It makes the work of the cross even more incredible and it makes the idea that God is looking for redemption from us more complete. We are not talking simply about the idea of physically living forever because that’s clearly not what it means. We know that we are going to physically die. All of us. But when you think about it in terms of what that means psychologically, spiritually, emotionally, socially, vocationally and so on it becomes a huge picture. The text is teaching us something which is real, which is true, which is there. I think we just need a bigger more sophisticated handling of the text, than a reductionist one that I think actually impoverishes or understanding of The Fall, the cross, redemption, the ‘coming again’ and so on.