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.

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

As Christians and geologists, we frequently encounter people with stories of storm tossed and shipwrecked faith that started when they began to wrestle with apparent conflicts between science and the Bible. The stories have a common thread. The Bible, they were told, clearly teaches the earth was created a few thousand years ago with life forms fashioned more or less as we find them today. Because the earth is very young, the incredibly complex sequence of rock, sediment, and fossils found on our planet must have been deposited in a very short period of time. Noah’s Flood, as the only plausible causal agent, was obviously a global and violent event. Theories of an ancient earth and adaptation of life forms, they were further informed, have been constructed on flimsy evidence created by atheistic scientists searching for ways to expunge God from modern culture. But as these sojourners began to explore and understand the actual evidence for an ancient earth, they found themselves increasingly convinced of its legitimacy, and thereby increasingly questioning the veracity of their faith – many to the point of relegating Christ to just another wishful myth.

It is our conviction that these stories of strained or lost faith derive not from an inherent unwillingness to trust the Bible, but rather from misguided teaching on the message of Scripture. Those insisting the earth is young are not simply putting their faith in God’s Word, they are putting their faith in their own particular interpretation of that Word. As such, an entirely unnecessary stumbling block to faith is created, where faith in Christ first requires rejection of sound science.

As we have prayed and studied this subject, we have felt God’s call to speak out against this misplaced stumbling block. We are sensitive, however, to the fact that when scientists speak on issues of faith, there is a natural suspicion that science will be regarded as the ultimate arbiter of truth, and Scripture will have to yield whenever conflict arises. It is thus important for us to state here that both of us ascribe to the authority and inspiration of Scripture, the reality and necessity of Christ’s death and resurrection, the existence of genuine miraculous events, and the truthfulness of the Biblical historical narratives. In our understanding, science will never trump Scripture, but by virtue of science being a study of God’s natural creation, it may occasionally assist in our understanding of God’s written Word. Where this has occurred historically and has been accepted by the Church, the invariable result has been the abandonment of an interpretation of some secondary importance, without any change in our understanding of the intended central message.

This phenomenon is illustrated well by the 17th century clash between Galileo’s claims that the earth revolves around the sun, and the multiple passages in Scripture that appear to clearly present a static earth as the physical center of God’s natural creation. The Bible tells us repeatedly that the earth is fixed upon its foundations (Ps 93:1, 104:5) and the sun rises and sets (Eccl 1:5, Ps 19:6). Within the context of the historical narratives (which we are not accustomed to interpreting in any figurative manner) we read statements about “the sun rising over the land” (Gen 19:23), and a miraculous event during a famous battle where “the sun stopped in the middle of the sky and delayed going down a full day” (Josh 10:13). Likewise in the Levitical law, we find commands to complete the Passover sacrifice “when the sun goes down” (Deut 16:6).

God’s people had interpreted these verses for thousands of years to be authoritative statements about both spiritual and physical realms, and 17th century believers understandably struggled with allowing science to alter traditional interpretations. If God says the sun rises and the sun sets, how could it be otherwise?

Fast forward a few centuries, and we are now somehow quite content to have allowed science to alter our thinking on these verses, without abandoning notions of inerrancy or inspiration. The reason is simply because it was eventually recognized that the primary message of these verses was never on the nature of nature, but on the nature of man and his experience with his environment and his God. Solomon and Joshua accurately recorded their experience from an earthly perspective (sun rising and setting), and David praised God for holding the earth fixedly in His hand (Ps 93:1, 104:5), without requiring a meaning of fixity in space. The central message of these verses was apparent to readers before and after Galileo. Only a secondary interpretation, likely never intended by the writers, was cast off after scientific advances.

So what is the issue regarding Noah’s Flood? The modern debate centers around two questions. Was it truly global in extent, and can the Flood account for the earth’s complex geologic record? To address the first, it is worth being reminded of the Apostle Paul’s letter to the church in Rome where he makes a statement that “your faith is being proclaimed throughout the whole world” (Rom 1:8). Entire people groups existed at this time in China, Australia, and North and South America who knew nothing of the church in Rome. Though using wording that literally means the entire world population, Paul is clearly referring to the world known to him and his readers at the time.¹ Paul speaks truthfully from his experience. Allowing for the possibility that Noah’s Flood encompassed all of known humanity without necessarily covering the entire planet is thus consistent with how other passages in Scripture are interpreted by Christians who believe the Bible is authoritative and trustworthy.

Our primary interest in this blog series is the second question, the widely promulgated notion that the Flood can account for the earth’s complex geology, and that all genuine Christians should accept this viewpoint.

Notes

1. Many Biblical scholars define a literal interpretation as one that takes into account the literary genre, figures of speech, context, and author/audience perspective in deriving the intended meaning. By this definition, poetry and allegory are literally interpreted as figurative. In this blog and in our article, our use of literal conforms to its more common definition where a literal interpretation is one that adheres to the precise definition of words without figurative meaning and without requiring additional context to understand.

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.

Today's video features pastor Brian McLaren and is courtesy of filmmaker Ryan Pettey, director/editor of Satellite Pictures.

In today's video, Brian McLaren discusses the value of considering Scripture in light of the cultures that surrounded them. The Biblical writers were aware of the myths of the power nations that surrounded them, but flipped their stories on their heads to reveal truth about God. The myths of cultures like Babylon declared that the world was built on a foundation of violence and humans meant to be slaves to the gods and their leaders, but the Bible tells that the world comes from goodness and that humans are made for more than servitude but to truly know God.

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.

The early chapters of Genesis appear to pose scientific problems that challenge our literal, post-Enlightenment lens through which we often read the Word of God. (See this post for a commentary on how this situation came about.) This leads many people to believe that the descriptions in these texts are meant to reveal more than raw scientific fact. Pete Shaw of Crosswalk Community Church highlights the story of Noah and the Ark to explore the possible reasons for adopting a non-literal understanding of this ancient narrative. Shaw first summarizes the story of Upnashatim in the Epic of Gilgamesh, a famous Sumerian flood story that the young and old in Abraham’s day would have known well. Upon comparison, these two accounts—the Genesis flood and the Gilgamesh flood—are incredibly similar. Furthermore, Shaw exposes the various practical problems that arise if one takes every word of the Noah story to be a precise truth. For example, he wonders how Noah could have fed and maintained every living land creature in a small boat for ten months. He also explains how a primitive understanding of the universe is heavily reflected in this text. In light of these points, he concludes that whether or not this story is portraying actual historical events, it is presenting rich truths about God, and that should be the focus of the believer.

Transcript

“The first eleven chapters of Genesis are what scholars call pre-history. In other words, they can’t really date what was going on very well in those first elven chapters. After that, twelfth chapter on, it is a lot easier to date, and the stories have a different feel, a different structure… but those first eleven have caused a lot of debate over the years. In fact, the next slide is going to kind of give you the line of where I am going to take you today. You might not be aware of this, but there is a Noah controversy. You and I, when we hear the story of a great flood, the first thing that comes to our mind—when we think of the whopper of all whoppers—we think of Noah and the Ark, but if we lived in Abraham’s time or especially before, the name Noah probably would not have come up. In fact, if we grew up with Abraham, the story we would have most likely known about was the story—I am going to butcher this name—of Utnapishtim.

You are familiar with Utnapishtim aren’t you? And you are familiar with the god Enlil. I am sure you are familiar with Enlil. And you would have been very aware of a storybook that was read by children and adults alike called the Epic of Gilgamesh. And in the eleventh tablet of the Epic of Gilgamesh, we have the story of Utnapishtim and the god Enlil. And just so that you would know about that story a little bit, knowing that that would have been the predominant story that you would have understood anytime you thought about a flood, this is how the story went down. So, this god Enlil was the god of thunder and rain and all that and he was not a happy camper (kind of temperamental) as thunder gods can be. And for no clear reason, except to mess around with some of the other gods in his discontent, he made the decision that he was going to wipe out the earth with a great flood. And one of the other gods, a goddess in fact, did not like that this was going to happen and thought that it was unfair, unjust, and so she sent a message to Utnapishtim that this flood was going to come at the hand and the wrath of Enlil. And so Utnapishtim got to work, and he built a vessel (a strange vessel), a cube, but he used some of the similar materials that we saw in the Ark, and he made this massive structure (if in fact you do the math, it is probably at least twice, if not much larger, than the actual Ark) this massive cube that he made hoping that it would float, and he got it done on time.

The rain didn’t come down for forty days, it came down just for seven, but it flooded everything out, and the only survivor was Utnapishtim. And when Enlil came around and saw that some human beings had survived, he was very upset because he intended to wipe out everybody to show his wrath and his anger to the world and to show that he was upset to all the gods in heaven. Well, Utnapishtim obviously saved his own life, the life of his family, the life of his personal animals because those are the animals that he saved—not the rest of the animals of the world. And he took some carpenters along because he didn’t know how to build stuff and once you are starting over you have got to build stuff, and so he brought some carpenters along. In honor of his faithfulness (in light of this word from the goddess) he was given divinity. And so, he became a god, he became one of the gods, he got to reside in heaven, if you will, because of his faithfulness…interesting story.

If you grew up in Sumer, which is present day Iraq, and you grew up with Abraham in what is present day Baghdad that would have been the story that you would have known very, very well. It is because that story exists and other cultures have their own flood stories as well that some scholars look at the story of Noah and the Ark, and they think, ‘well, gee, how should we really interpret this thing? You know, our Enlightenment and post-Enlightenment perspective says it is in black and white, and if it says that is what happened, then that is exactly what happened. There is no way around it.’ Well, what if the first people who shared this story with each other and what if the early writers of this word, what if when they approached the Bible, they didn’t approach it the way we do? What if they didn’t approach the Bible, the Word of God, as a literal, this is exactly how it happened book that our post- Enlightenment eyes are framed to do? How would that change us? And also, some of the things that some of the challengers of this story are bringing out are some of the issues with the story like ok is this really a big enough boat to handle all of the creatures of creation…can they really, really fit?

Some have really tried to make a case that there weren’t as many animals back then as there are now because they got together and hooked up, and now, we have all kinds of varieties and that kind of thing. And so that is kind of there, but you are talking ten months of time! How do you feed all the animals of the world? How do you store all the food? Did they eat fish, because the fish didn’t die? The fish lived on just fine. How do you do that? And what about—it is kind of unpleasant—but all the excrement? What are you going to do with all that ‘bleep?’ Are you going to throw it out the eighteen inch window at the top? Did they have a conveyor belt system? How did it work? And so they look at that and think, ‘I am just not sure about that.’ Would you really take that literally? Is that how we should take it? Is that how they took it around their campfires and around their dinner tables? Did they think about it that way?

And there are other issues too that academics look at, and they challenge somewhat. Like they know that forty days and forty nights is a proverbial statement in Jewish culture. It was like saying (and you see it in many accounts in the Bible), forty days and forty nights was saying a long time, but it probably was not meant to be taken literally. It is just a long time. It is how they thought about things. Then, there is the issue of the rain itself, and how it all came down. Now, the New Living Translation and most modern translations, just simply talk about it as--there is the sky and the rain came down from the sky and you are good to go. But there is another word that is used. If you go to the New King James Bible, for instance, and they talk about the firmament—that the rain came down from the firmament. And so, when we think about firmament, we think, ‘well they are talking about sky or they are talking about the starry host and all that stuff,’ but if we go back to the original word, which the New American Standard version got right (it is one of the most academic and precise versions that is out there), both in the creation story and in the Noah account, they use a different word for sky: they use the word dome.

Now, I am going to butcher this a little bit, but broad stroke version is that the way the ancient people saw the world was that we kind of lived in this bubble, you know sort of like a snow globe, and there was water--not all inside, but outside, surrounding us. There was water below and there was water above, and above us was this massive dome called the firmament or called the sky. And then when it rained it was because God was opening up the floodgates of heaven. That is how they thought back then. They didn’t know any better. And so, kind of what these questions are asking us now is how we make sense of this and do we have to believe like they did in order to believe the story. How many of you believe that the sun revolves around the earth? None! Nobody does. Do you get mad at, do any of you hold a grudge against the earliest people in the Bible, actually, all the people in the Bible, do you hold them accountable and are you angry at them that they believed with everything in them that the sun revolved around the earth and not the other way around?... no, of course not. Do you get angry at them because they believed we lived in a dome and that God opened up the gates of heaven and there you go? No, you don’t hold it against them because you understand that it is the best that they could do given their time.

But we live in the age of Doppler radar, right? We know within minutes, you know, when rain is going to hit Napa and when it is going to move on to Valeo, and so on and so forth. I mean it is that precise, and we know when it is coming hundreds of miles off shore and we can look thousands of miles because of satellite stuff and our ability to understand temperatures and all that. We know how the whole thing is brewing. We know that hurricanes are lining up one after the other in hurricane season because we have cameras up there that are seeing them start to form, and we can gauge temperature in the water and so forth—we do not live back then. So, it would be inappropriate for us to become primitive in the sense of looking at the world the same way they did in that kind of a literalness because we know different, you know what I mean? We know different. And so really the bottom line is that the literalness of the story really isn’t the most important thing to begin with anyway.”

A few editorial reflective thoughts by Darrel Falk: The sermon continues, of course, and you can download it at the above link. What is "the most important thing" to which Pastor Shaw refers as the audio clip draws to a close? Regardless of whether you think it is historical or not, what is the message that God wants to communicate to us through this story? Consider reading Genesis 9 right now. What are the parallels in this "recreation"account to the original creation account? What does God want us to see in making those parallels? What about the rainbow? What does it symbolize for you? Can you sense God's love for all of creation (not just humankind) as this story draws to a close? Why does the story of Noah himself, however, not have a happier ending? Have we seen the theme of nakedness and the need to cover up nakedness in an earlier scriptural passage? Why do you think the story of Noah draws us back to this point (nakedness and shame), just like the story Adam and Eve does? What brought on shame for them? What brings on shame for us? Do you see that God is wanting us to think deeply about this story and its meaning? What is another example of the need to cover up? (Hint: think Moses.) What difference does the coming of Jesus make to all of this? (Hint: see II Corinthians 3:12-18.) Do you see the rainbow?]]> Sat, 12 Nov 11 04:00:15 -0800 Pete Shaw http://biologos.org/blog/what-does-the-fossil-record-show?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/what-does-the-fossil-record-show?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication Organisms have changed significantly over time. In rocks more than 1 billion years old, only fossils of single-celled organisms are found. Moving to rocks that are about 550 million years old, fossils of simple, multicellular animals can be found. Yesterday, in our BioLogos podcast, we looked at the question of transitional fossils. Today, to follow-up, we’d like to repost our recently revised FAQ on the fossil record – one of ten Questions we’ve updated. We’ve also edited how the Questions are organized, to help readers more easily find answers to the topics they care about, from explaining the BioLogos view to responding to arguments against God and Christianity. If you haven’t yet, we encourage you to take a look at the changes!

Evidence of Gradual Change

Organisms have changed significantly over time. In rocks more than 1 billion years old, only fossils of single-celled organisms are found. Moving to rocks that are about 550 million years old, fossils of simple, multicellular animals can be found. At 500 million years ago, ancient fish without jawbones surface; and at 400 million years ago, fish with jaws are found. Gradually, new animals appear: amphibians at 350 million years ago, reptiles at 300 million years ago, mammals at 230 million years ago, and birds at 150 million years ago.¹ As the rocks become more and more recent, the fossils look increasingly like the animals we observe today.

The Transition to Land: Sea Creatures to Land Animals

Fossils of land animals, or tetrapods, first appear in rocks that are about 370 million years old. In older rocks, only sea creatures are found. But in 1998, scientists found a fossilized fin, 370 million years old, with eight digits similar to the five fingers humans have on their hands, as shown in Figure 1. However, the fin was undoubtedly that of a fish, which means this fossil is strong evidence of a transitional form.

Figure 1:An Illustration of the fossilized fin found in 1998. Its resemblance to a tetrapod is an indication of gradual evolutionary change from sea creatures to land animals. Source: Image is used by permission from Falk, Coming to Peace, 113.

One of the great success stories in the examination of the fossil record was the finding of a near-perfect fossilized transition between a vertebrate adapted for water and one adapted for land. Evolutionary biologist Neal Shubin set out to find a more complete transitional specimen than the 1998 fin. He determined the exact age of rock that he expected would yield a transitional land/water animal, and then he and his team spent four summers in the Arctic scouring rocks of that age to find one. The results (see Figure 2 below) were spectacular.²

From Reptiles to Mammals

Mammals first appeared in the fossil record about 230 million years ago, nearly 70 million years after reptiles first appeared. One group of reptiles, the cynodonts, first appeared about 260 million years ago and became increasingly mammal-like in more recent fossils—circa 245 million years ago. This change can be seen most clearly in the bone structure of the ear, as illustrated in Figure 3.

Figure 3: As shown in the image above, transitional fossils of cynodonts had two jaw hinges. These fossils date from a time when the dentary and squamosal bones were beginning to take over the role of jaw hinge (hinge #2). This allowed the articular and quadrate bones to evolve into the second and third bones of the mammalian ear, as shown on the right. Source: Image used by permission from Falk, Coming to Peace, 119. Originally from F. H. Pough, J. B. Heiser, and W. N. McFarland, Vertebrate Life, 4th ed. (Upper Saddle River, NJ: Prentice Hall, 1996), 607.

Scientists found a species of cynodonts, dating to just before the emergence of mammals, that had a double jaw hinge like that of a mammal. A pair of bones found in even earlier cynodont fossils seems to have transitioned slowly into the ear. No other fossils have been found that share a similar structure to the transitional cynodonts and date back before the time of mammals. Likewise, soon after mammals appeared, these cynodonts became extinct. This timing implies that the cynodont fossils record the transition from reptiles to mammals.³

Transitional Forms: Few and Far Between

Transitional forms occur just when one might expect to see a change from one body type to another. However, a common objection is that few transitional fossils have been discovered; thus many lineages cannot be traced smoothly.

There are several reason for these gaps in the fossil record. First, fossilization is a very rare event. Plus, transitional species tend to appear in small populations, where rapid changes in the environment can provide a stronger evolutionary drive. Finally, because fossilization itself is a rare event, smaller populations are sure to produce fewer fossils. The fact that transitional species have been found at all is remarkable, and it offers further support of gradual, evolutionary change.

Notes

1. Darrel Falk, Coming to Peace with Science, 83-84.
2. For a discussion of the science and the story of the discovery, see Darrel Falk, “In the Bones” (July 29, 2009), (accessed 10/21/2011) and Stephen Matheson, “New Limbs from Old Fins, Part 2” (Sept 16, 2011), (accessed 10/21/2011). Shubin’s 2008 book Your Inner Fish (Pantheon) is also very good.
3. Falk, Coming to Peace, 115–120; F. H. Pough, J. B. Heiser, and W. N. McFarland, Vertebrate Life, 4th ed. (Upper Saddle River, NJ: Prentice Hall, 1996), 607; M. J. Benton, Vertebrate Palaeontology: Biology and Evolution (London: Unwin Hyman, 1990), 228–231; E. H. Colbert, M. Morales, and E. C. Minkoff, Colbert’s Evolution of the Vertebrates: A History of the Backboned Animals Through Time (New York: Wiley-Liss, 2001), 274–277; T. S. Kemp, The Origin and Evolution of Mammals (New York: Oxford University Press, 2005), 75–78.

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As you might have guessed, tetrapods are vertebrate animals that have four limbs. The group includes reptiles, amphibians, birds, mammals... you know, the usual suspects. (Snakes and whales, which don't have those limbs, are nonetheless classified as tetrapods, and we'll come back to that.) At first, this might look like a wildly diverse crowd of animals with almost nothing in common: tiny hummingbirds in the air, gigantic whales in the ocean, frogs that come from tadpoles, salamanders that can regrow severed limbs, cats that eat only other vertebrates, misnamed “bears” that eat only eucalyptus leaves. But on closer inspection, some extraordinary patterns emerge. These animals, in all of their magnificent variety, seem to be built in very similar ways. It's as though some kind of master plan has been tweaked over and over, to make a huge collection of variations on a theme.

This master plan for building tetrapods includes numerous components: plans for building backbones, for making skin, for growing a brain. Some of those components are unique to tetrapods; some are more widely employed in animals. Our focus will be the one that is most clearly associated with the tetrapods. We will explore the building of limbs – arms, legs, wings and flippers; and hands, feet, paws and paddles.

Consider, then, the human forelimb, better known as the arm. You may already be familiar with its skeletal structure, nicely illustrated in the 17th-century chalk drawing below.

The upper arm contains a single large bone, the humerus, which is attached to the shoulder and to the elbow. The lower arm sports two parallel bones: the radius and the ulna. Those two bones link the elbow to the wrist. The wrist is composed of a group of small bones called the carpals (made famous by Carpal Tunnel Syndrome, which is reportedly exacerbated by the typing of blog posts). Attached to the carpals are the metacarpals, which are the bones of the fingers. So, the skeletal components of the human arm are as follows: one bone (humerus) attached to two bones (radius and ulna) attached to a set of small blocky bones (the carpals), which anchor finger bones. It's an interesting pattern, but all by itself it's not necessarily remarkable.

Now let's look at the human hindlimb, or leg. The bones have a different set of names, which you may know all too well. Have a look at the 19-century illustration below.

The upper leg contains a single large bone, the femur, which is attached to the hip and to the knee. The lower leg sports two parallel bones: the tibia and the fibula. Those two bones link the knee to the ankle and foot. The ankle and foot are composed of a group of bones that includes a set of small bones called the tarsals. Attached to the tarsals are the metatarsals, which are the bones of the toes. So, the skeletal components of the human leg are as follows: one bone (femur) attached to two bones (tibia and fibula) attached to a set of smaller blocky bones (tarsals and others), which anchor toe bones. It's an interesting pattern, but all by itself it's not necessarily remarkable.

But wait. The leg pattern is essentially identical to the arm pattern. Why just one pattern? Why that pattern? Is there something special, maybe even somehow universal, about the pattern?

Questions like those were the domain of the great Richard Owen, the British naturalist and contemporary of Darwin. Owen's detailed study of limb structure led him to write one of the more influential works in the history of biology: On the Nature of Limbs, first published in 1849 and most recently reprinted in 2007. In that book, Owen argued that all vertebrate limbs were modifications of a basic pattern or plan, called an archetype.

To see why Owen reached this conclusion, consider the wonderful lithograph below, created in Owen's time (1860) by Benjamin Waterhouse Hawkins, who also contributed illustrations to Darwin's Zoology of the Voyage of the HMS Beagle. The limbs of the horse are constructed in an interesting pattern, depicted in the upper left. One large bone is attached to two parallel bones that have fused over most of their length. Those two bones attach to a collection of bones which then attach to some longer bones that form the ends of the limbs.

The pattern is much more striking when the limbs of diverse vertebrates are compared. Have a look at these two illustrations from On the Nature of Limbs. One is a dugong, a large aquatic mammal, and the other is a mole, a tiny mammal known for burrowing and defacing lawns. Do you see the pattern? One bone attaches to two bones which attach to blocky bones that support digits.

That pattern applies to bat wings and whale flippers and frog legs and chicken feet. It applies to dinosaurs and to newts. It's a universal feature of tetrapod limbs, front and back. Neil Shubin, in his brilliant book Your Inner Fish, summarizes the pattern as a simple chant: one bone, two bones, little blobs, digits. Owen's great insight was this: limbs are built according to a common pattern. One bone, two bones, blobs, digits.

Now, that's a remarkable fact about the animal world, and we curious hominids are itching for an explanation. Why are all tetrapod limbs based on the same underlying pattern?

We can use Owen and Darwin to sketch the two main competing explanations: design and descent. In the simple version of the story, Owen the anti-evolutionist, the design theorist of his day, concluded that the archetype was a design, a basic idea in the mind of the Creator. Darwin, of course, proposed a radically different explanation: the “archetype” is a common ancestor, and the variations on that “theme” are exemplars of descent with modification. There's no design, no Creator, just a lot of gradual tinkering with a setup that worked well enough at some time in the distant past.

That outline is hopelessly simplistic. Owen's views on evolution were complex and malleable; indeed, he got in some trouble for suggesting that tetrapods (even humans) were descended from fish through “slow and stately steps, guided by the archetypal light.” Later in life, in the midst of various nasty disputes with contemporaries (most notably with T.H. Huxley, known affectionately as “Darwin's Bulldog”), Owen did seem to oppose evolutionary ideas. But his writing in 1849 shows that he could see no reason to reject common ancestry while exploring the nature of the archetype. In other words, Owen was, at least earlier in his career, comfortable with common ancestry alongside strong conceptions of design.

And that is one theme that we will explore in this series. We will examine the evolution and development of limbs, to see how evolutionary explanations work and how strong and multidisciplinary the evidence for common descent really is. Common descent, I will argue, is really true, at least because it provides vast explanatory resources to those seeking to understand tetrapod limbs. But what about design? Can design also contribute explanatory resources? It's one thing to assert that the limb-construction blueprint proceeds from the mind of God; it's another thing to propose it as an explanation for why limbs are the way they are. Is there something about that plan – one bone, two bones, blobs, digits – that is superior? Could it have been otherwise? Those questions, I think, are the ones that we must address before we can advance design as an adjunct to – or a replacement for – common descent.

With those ideas in mind, let's explore the evolution of limbs. In the next post, we will explore the origins of those limbs, following the long search for their predecessors in the deep past and culminating in one of the most dramatic fossil finds in scientific history. In the third post, we will look at evidence from anatomy and developmental biology that supports the contention that fish fins and tetrapod limbs are variations on a theme. The fourth post will build on the third, looking at fascinating commonalities in the genetic systems that underlie the development of fins and limbs. In the fifth post, we will look at brand-new findings from developmental genetics that solidify and expand the fin-limb connection. The sixth and final post will look at the surprising links between fins, limbs and all other animal appendages, and will address oddities such as lost limbs in whales.

Bring your curiosity and your questions!

Further Reading

Neil Shubin (2009) Your Inner Fish: A Journey Into the 3.5-Billion-Year History of the Human Body. New York: Vintage Books.

Brian K. Hall, editor (2007) Fins into Limbs. Chicago: The University of Chicago Press.

Richard Owen (1849) On the Nature of Limbs. London: John Van Noorst. (Google eBook).

Brian Switek (2008) Richard Owen, the forgotten evolutionist. Blog entry at Laelaps.

Carl Zimmer (1999) At the Water's Edge. New York: Simon and Schuster.

Image Credits

The first three images (human arm, human leg, man on horse) are courtesy of Wellcome Images, Creative Commons license. The last two images are taken from On the Nature of Limbs (1849), free online at Google eBooks.

Despite all the other possible avenues to explore in thinking about natural teleology, I’d like to follow up on the discussion begun last week around John Leax’s poem “the clever trout,” in which I expanded on the poet’s suggestion that creation gives worship by being itself as it was created to be. Is that sort of “simply being” really just responding to survival threats and opportunities? Is the trout just finding food, the popple just resisting wind, and the jay just avoiding predators, though they be sustained by the Spirit? A couple of recent opportunities to examine the relationship between people and dogs (and my own dog, in fact) have served as reminders that purpose is much more than problem-solving while elucidating another aspect of mankind’s particular call to know and engage with the rest of God’s creation—that of cultivation, and even partnership.

The remarkable cooperative relationship between humans and canines was the subject of the most recent edition of the venerable science television show NOVA, which examined an expanding scientific interest in the study both of the natural history of the domesticated dog and of the physiological capabilities that have made it so successful in the company of people. The show discussed new research detailing dogs’ ability to scan human faces for emotional cues, for instance, and studies showing that humans can understand different barks and vocalizations which developed as a way to communicate with people rather than with other dogs.

As one would guess from the title, “Dogs Decoded” places a slight emphasis on the information gleaned from genetic analysis of dogs with regards both to their evolutionary history and potential current usefulness in the understanding of human diseases, but of most interest here are a few claims about the importance of dog domestication for the development of human culture. One speaker—University of Durham archaeologist Greger Larsen—goes so far as to claim that civilization would have been impossible were it not for canine help in the early herding stage, while Larsen’s colleague Peter Rowley-Conwy agreed and suggested that the relationship began as a mutually beneficial hunting partnership, both species being more efficient in bringing down large game in cooperative hunts with the other, thereby gaining a reproductive advantage. As a counter-theme, though, the program spent even more time discussing the way the process of domestication—a kind of “un-natural selection”—has “infantilized” modern dogs, selecting for physical traits that we regard as “cute,” even while equipping them with genetically-based skills of communicating with humans.

While dramatic (sometimes contradictory) claims are the standard fare of popular science television, what was remarkable about the program was the gulf between the suggested origins of domestication (in cooperative hunting) and the apparent “results” of the process—animals described almost exclusively as pets, companions, and even surrogate children. Surprisingly little mention was made of the long history and continued role of “working dogs” who retain specific traits and abilities from their “natural” state and exercise them regularly in cooperation with humans, or what emotional content such relationships might entail. While the term co-evolution was used for dogs and humans emerging into modern history together, the discussion of intentionality and purpose (in both humans and dogs) in the process of domestication was all but unexplored—a little disappointing considering to program’s focus on the abilities of dogs and people to understand each other’s emotions and intentions.

Into that “working dog” gap comes my own recent experiences with Griffin, our 16-month old Springer Spaniel, pictured above when just over a year old, on alert for geese in the grass along the James River. While Griffin is every bit as domesticated as the dogs discussed in the NOVA program and likes almost nothing better than to sleep on the sofa with any or all members of his family, what he does like better is hearkening back to his primordial canine job of hunting. In his case, hunting means locating, flushing (or “springing”) and then retrieving downed birds or other prey in partnership with his handler and other shooters. Like other hunting breeds, Spaniels are trained how to stay the proper distance from their human companions to keep birds in gun range, but also in order to receive instructions via voice or whistle, gesture, and eye contact.

These specific behaviors and the physical attributes bred to make them more efficient in practice mean that Griffin is as much a cultural artifact as a product of nature, though as “Dogs Decoded” made clear (and generations of sporting dog breeders and trainers agree), culture and training must have a basis in genetics. The critical point here is that nature and nurture have combined to produce something beautiful and remarkable: not just the dog himself, not even the elegant way he fulfills his half of our partnership by finding birds and putting them to wing, but the palpable sense of joy he communicates when he is doing what he was literally “made to do.” To begin circling around again to the idea that “purpose” is more than just solving a problem, Springers may have been bred initially to help in hunting birds hiding in the underbrush, but the end result of generations of guided evolution of the breed is not a product or even a practice, but a relationship.

Though only dogs seem to have had the right combination of traits to achieve the level of communication and emotional attachment to humans that dog owners everywhere take for granted, the kind of careful observation, understanding, and imagination our human forebears paid these once-wild creatures need not be limited to them alone. Indeed, the continuation of the meditation on human identity and the imago Dei begun with Leax’s poem last week is that laying aside our desires for glory ought to lead to a more grace-filled exercise of our dominion, a sense that we can and should seek the shalom of the creation first by seeking to understand it and appreciate it as it truly is.

To borrow from the language of the contemporary church, it is often said that the goal of ministry should not be to figure out what we can “do for the Lord,” but to discern what the Lord is already doing through the Spirit and join into that effort. Sometimes that means taking the time to recognize patterns, potential, possibility rather than just needs to be filled, problems to be fixed. God’s work, after all, is not just a problem-solving practice (despite the centrality of Jesus’ own saving and restoring work), but one of beauty and synthesis, of bringing things together in new ways for greater relationship in scale and complexity, for His ultimate glory in the New Jerusalem. If the defining experience in that day will be worship and joy throughout the creation, perhaps we can learn to recognize—even in the eyes of our canine companions—what makes for joy and worship in the creation now, as well.