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.

Transitional Fossils

Some time ago, the Discovery Institute’s Casey Luskin commented on the human origins exhibit at the Smithsonian Institution, suggesting that palaeoanthropologists use evolutionary theory to describe the progression of the human lineage even when they don’t have transitional fossils with which to work. He writes:

What's ironic, however, is that if you ask the question How Do We Know Humans Evolved? the answer you’re given is, “Fossils like the ones shown in our Human Fossils Gallery provide evidence that modern humans evolved from earlier humans.” So whether you find fossils or you don’t, that’s evidence for evolution.

Indeed, it has become an article of faith for those espousing both the young earth creation (hereafter YEC) model and many who hold to the intelligent design model that transitional fossils do not exist and therefore evolution has not taken place. Support for this position usually entails attacking the weak areas of the fossil record, where burial processes have left us little with which to work, or the creation of straw men arguments in which transitional fossils are defined in such a way that none could ever be found. Often this centers on the concept of “missing link,” a term that is habitually used in the popular press and young earth creation and intelligent design literature when referring to fossil remains but which has little to no meaning for biologists or palaeontologists. As Ahlberg and Clack (Ahlberg and Clack 2006) write:

But the concept has become freighted with unfounded notions of evolutionary ‘progress’ and with a mistaken emphasis on the single intermediate fossil as the key to understanding evolutionary transitions. Much of the importance of transitional fossils actually lies in how they resemble and differ from their nearest neighbours in the phylogenetic tree, and in the picture of change that emerges from this pattern.

Contrary to common misconceptions, the fossil record does not record one single lineage for any family of organisms but rather a series of branches, with many related species coexisting synchronously. Darwin hypothesized that the evolutionary record reflected this bushiness and drew such a diagram in his journal. At the time, though, he had little in the way of fossil evidence to back up this position. Much has changed since his day.

An analogy for understanding this “bushiness” was best described by Prothero and Buell (Prothero and Buell 2007). They suggest that the reader consider his or her own genealogy. You and your siblings are the direct descendents of your parents and, while you are similar to them, each of you has different characteristics not shared with them as well as characteristics that you do share. Your parents have siblings as well (your aunts and uncles), and your grandparents are their last common ancestors. These siblings have their own children (your cousins), who have different and similar traits relative to their parents. They are broadly recognizable as being related to you (“oh, I see you have Aunt Edna’s nose”) but three or four generations out, they will become less and less so. These are the “nearest neighbours” that Ahlberg and Clack describe. In this analogy, each of these cousins represents a transitional form from what was (your grandparents) to what will be down the road.

For example, no one would confuse a frog with a salamander but if you trace the fossil record of each back in time, eventually you encounter a fossil, Gerobatrachus hottoni which was recently discovered (Anderson et al. 2008) that is best described as a “frogamander,” having the basal characteristics of both frogs and salamanders. Had we seen such an animal at the time, it is likely we would not have found it remarkable because it would have resembled the species around it. One lineage eventually diverged into frogs, salamanders and other amphibians. Most (just like Darwin proposed in his tree diagram with the little hatch marks at the tip of many branches) went extinct.

Taxonomy and the Beginnings of Human Origins

All life is classified based on a system devised by Carolus Linneaus in 1735 in his remarkable work Systema Naturae. This system gives all recognized species an individual place based on a system of hierarchy. The study of classification is known as taxonomy. A taxonomic ranking for humans would be this:

When a fossil is excavated, the first thing that the palaeontologist does is make a taxonomic assessment of where it fits in a sequence of known fossils. Traits that are shared with other like species or genera are referred to as primitive traits. Examples of this in humans are five fingers and the presence of three arm bones. We share this with all mammals. Traits that are new or are not shared with other like species are referred to as derived traits. Examples of this in humans are the skeletal changes in the pelvis and the foot to allow for walking upright. We do not share these with any other primates.

Transitional fossils in the human fossil record are distinguished at both the genus and species level. This group includes the extinct genera Ardipithecus and Australopithecus and the current genus Homo. All species except Homo sapiens are extinct. Much of the recent study of early humans focuses on the transition from Ardipithecus (‘Ardi’) to Australopithecus (‘Lucy’ and similar fossils) and from Australopithecus to Homo, the genus that led eventually to us. While each of the australopithecine species identified in the fossil record has derived characteristics that separate them from their ancestors and from each other, only one led to the genus Homo.

In future posts, I will describe the evidence for human evolution and why this evidence is compelling. It suggests that we have had a long, varied history filled with great leaps of change, crushing defeat, and eventual expansion into all areas of the globe.

Notes

Ahlberg, P. & J. Clack (2006) A firm step from water to land. Nature, 440.

Anderson, J. S., R. R. Reisz, D. Scott, N. B. Frobisch & S. S. Sumida (2008) A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders. Nature, 453, 515-518.

Prothero, D. & C. Buell. 2007. Evolution: What the fossils say and why it matters. Columbia Univ Pr.

Introduction

One of the reasons that some of us are hesitant to accept evolutionary creation is that it seems to make God responsible for the suffering and death of innumerable creatures over millions of years—before humans ever existed or sinned against their creator. Since we believe in and worship a God who is loving, benevolent, and all-powerful, it sounds quite implausible that our God would have created a world like that; therefore, any scientific evidence for evolution must be incorrect.

Other people look at the scientific evidence for evolution and find a compelling case that it has taken place during our earth's history. On this basis they may conclude that if evolution is true, then the belief in an all-powerful, perfectly good God must be false!

The trouble with both of these views is that they tend to invoke a completely abstract, philosophical god, not the living God of the Bible—the God who became a human being, experienced unimaginable suffering, and died in a grotesque and humiliating public display. The death of Jesus completely defied the expectations (and common sense) of his followers, as well as the expectations of any “rational” understanding of the way the Creator of the universe should act in the world. On the cross, in the person of Jesus, God took upon himself far more suffering than any creature has ever experienced.

If God himself is willing to die, particularly in such a gruesome way, then perhaps we should at least consider the possibility of God allowing the death of other creatures, too. But would this really be compatible with what we know of God through Scripture? In this essay, we will explore this quandary through a “theology of the cross”, a concept articulated by pastor George Murphy in his book Cosmos in the Light of the Cross.¹

Theology of the cross

Before we jump into the theological problems associated with evolution, let’s take a look at how we understand Christian theology itself. For the reformer Martin Luther, any theology (or science) that tries to reach knowledge of God apart from the cross is bad theology.² Instead, Luther pointed to a theologia crucis, in which the true God is seen first and foremost “through suffering and the cross”. To make his point even clearer, Luther insisted that “the CROSS alone is our theology”.³ It is the lens through which we view everything.

Of course Martin Luther, having lived in the 16th century, was not aware of the vast history of life on our planet (or any other aspect of modern science, for that matter), but George Murphy draws from Luther’s teachings the foundation that all human knowledge begins with the Word made flesh and crucified.⁴ With the cross of Christ as the ultimate framework through which we view reality, we are bound to view the processes of nature quite differently. As Murphy explains it,

A theology of the cross is an explication of belief in a God who becomes a participant in the history of the universe and thereby shares in the suffering, loss, and death that are part of worldly experience.⁵

God does not sit idly by and watch unaffected as his creatures suffer, but neither does he swoop in and make everything completely effortless and easy. Instead he chose another way, the crucifixion of Jesus—certainly not the approach that we would have preferred! The apostle Peter went so far as to try to talk Jesus out of it, but he was met with a stern rebuke (Matthew 16:21-23).

Why is evolution so disconcerting to Christians?

The problem of suffering throughout all of human history is troubling enough for us to reconcile with a loving, personal God. But in addition to that, the discovery of vast numbers of fossils reveals that death has taken place on a far greater scale than we had ever imagined. Both the wide variety of extinct creatures and their sheer numbers is quite staggering, and it raises questions about our Creator:

The picture of a God who is immune from suffering and death but who forces organisms through millions of generations and extinction is disturbing to those who believe in a God of love.⁷

The mass extinction of life on earth was already well established by the early 19th century—decades before Darwin’s research—and extinction can be empirically verified independent of any theory of evolution.⁸ The fact that the earth’s crust is a veritable graveyard of long-lost creatures is deeply troubling, and as late as the 1790’s, distinguished intellectuals such as Thomas Jefferson denied the very possibility of extinction.⁹

But in addition to the reality of species extinction, the theory of evolution by natural selection proposes that new species also arise in an environment containing widespread pain and death. Both the creatures that are now living and those that are gone are tainted by an “acrid smell of death”.¹⁰ It makes us wonder, if our Creator is not the God of the dead, but of the living (Mk. 12:27), where is God’s presence in the evolutionary picture?

In all honesty, creation through evolution is not what we would expect from God, but Scripture is full of examples in which God acts in unexpected ways. After all, God’s choosing to undergo an agonizing death on a cross is not what we would expect from the all-powerful Creator of the universe, either. In both cases, new life comes about through pain, suffering, and death. As George Murphy puts it,

A priori ideas about God have to be overcome, and God's character has to be learned from God's self-revelation.¹¹

God’s fullest self-expression is in Jesus Christ himself, one who is intimately familiar with and personally endured creaturely pain and death. The theology of the cross reveals that God's self-revelation takes place in situations of suffering, loss, and apparent hopelessness, much like situations that occur through natural selection.¹²

The crucifixion is disconcerting too

Not only is creation through evolution an unexpected and unsettling process, but so is the crucifixion of Jesus! Killing someone by hanging them on a cross is an unbearably painful, prolonged, humiliating form of death. It was such a horrific type of public execution that it wasn't until after the Roman Empire stopped the practice of crucifixion—and people no longer witnessed it personally—did the cross become a visual object of devotion.¹³ Our culture is sufficiently removed from crucifixion that we are desensitized to its original significance, but to connect it to our current context, imagine the reaction you would get by wearing jewelry designed to look like an electric chair.¹⁴

Once we are more attuned to the brutality of crucifixion, it seems all the more striking that the cross is the sign of God’s work, what George Murphy calls “the trademark of God”.¹⁵ The suffering and death of Jesus is featured prominently in the Gospels, but the crucifixion-resurrection pattern is strongly resonant within the Old Testament, too. Israel suffered and toiled as slaves in Egypt for centuries before they were rescued in the Exodus, bringing life to a people who were spiritually dead. Centuries later, the nation of Israel would experience death again when the Babylonians destroyed the Davidic monarchy, burned their Temple, killed their people, and sent many into exile.¹⁶ Neither Israel (God’s chosen people) nor Jesus (God’s own son) were spared from death and suffering; rather, suffering seems to have been the way in which God re-forms and renews humanity to fully bear His own image.

Redemption extends to all of creation

Fortunately, God’s story does not end with death. God gives new life after his creatures have been subjected to terrible circumstances. Redemption was promised to Israel itself—Ezekiel’s vision of the valley of dry bones describes how God would renew His chosen people (Ezek 37:1-14). Later, the astonishing resurrection of Jesus made salvation possible not only for Jews, but for all people in Christ (Gal 3:26-29). Ultimately, the New Testament makes it clear that God’s renewal will encompass the entire Creation:

For God was pleased to have all his fullness dwell in him, and through him to reconcile to himself all things, whether things on earth or things in heaven, by making peace through his blood, shed on the cross. (Colossians 1:19-20)

With all wisdom and understanding, he made known to us the mystery of his will according to his good pleasure, which he purposed in Christ, to be put into effect when the times reach their fulfillment—to bring unity to all things in heaven and on earth under Christ. (Ephesians 1:8-10)

Christians are accustomed to thinking of the death of Christ in regard to humans, but our culture rarely acknowledges God plan for the redemption of His entire creation. This is partly attributable to the fact that discussions of creation and origins are often separated from the topic of salvation.¹⁷ In doing so we tend to marginalize Jesus as we argue about Genesis. Rather than fall into this trap, if we view nature through a theology of the cross, we will see Christ as both the alpha and the omega point in discussions of life’s history and life’s future. With this perspective, we are more apt to sense our solidarity with the rest of creation as we wait in eager anticipation of a glorious future:

The creation waits in eager expectation for the children of God to be revealed. For the creation was subjected to frustration, not by its own choice, but by the will of the one who subjected it, in hope that the creation itself will be liberated from its bondage to decay and brought into the freedom and glory of the children of God. (Romans 8:19-21)

Conclusion

As part of the Church’s conversation about the problem of natural evil, this essay is meant to be a brief introduction to a “theology of the cross”. One can explore this concept in greater detail in Murphy’s book The Cosmos in the Light of the Cross. While there is a lot more to be said, let me conclude with the following observation: though evolution may not be compatible with some interpretations of Christianity, evolutionary creation is certainly compatible with the crucified Christ and the theology of the cross. In the person of Jesus, God suffers with the world and ultimately redeems it. As George Murphy puts in, “The world's pains are God's stigmata.”¹⁸

Explore this Topic Further

• Miller, Keith. “And God saw that it was good”: Death and Pain in the Created Order. BioLogos series
• Murphy, George L. The Cosmos in the Light of the Cross. Harrisburg, PA: Trinity Press, 2003.
• Murphy, George L. “Cross, Evolution, and Theodicy: Telling It Like It Is”. In The Evolution of Evil. Edited by G. Bennett, M.J. Hewlett, T. Peters, and R.J. Russell. Göttingen: Vandenhoeck & Ruprecht, 2008.
• Southgate, Christopher. The Groaning of Creation: God, Evolution, and the Problem of Evil. Louisville, KY: Westminister John Knox Press, 2008.

Notes

1. Murphy, George L. The Cosmos in the Light of the Cross. Harrisburg, PA: Trinity Press, 2003.
2. Murphy, p34
3. “CRUX Sola Est Nostra Theologia,” in D. Martin Luthers Werke, Kritische Gesammtausgabe (Weimar: Hermann Boehlau, 1892), 5:172. The captitalization is in the original. Cited in Murphy, p26.
4. Murphy, p108
5. Murphy, p4
6. Murphy, p43
7. Murphy, p3
8. Some Christians ascribe animal death to some combination of Adam’s fall and Noah’s flood, but this does not resolve the problem that the animals are still suffering and dying through no fault of their own. See Keith Miller’s BioLogos series Death and Pain in the Created Order for the limitations inherent in a fall-based theodicy.
9. Rudwick, Martin. The meaning of fossils: Episodes in the history of paleontology. Chicago, University of Chicago Press, 1985.
10. See Jeff Schloss’ BioLogos essay Evolution, Creation, and the Sting of Death
11. Murphy, p63
12. Murphy, p122
13. Murphy, p27
14. This example is drawn from an evangelical outreach event held by a Christian student group in Innsbruck, Austria. On campus one day, they started conversations with their classmates by asking the question, “Would you wear an electric chair on your neck?”
15. Murphy, George L. The Trademark of God: A Christian Course in Creation, Evolution, and Salvation. Wilton, Conn.: Morehouse-Barlow, 1986.
16. Murphy, Cosmos in the Light of the Cross, p 31-32.
17. Murphy, p35
18. Murphy, p87

The script was written by biology student Joy Walters, with help from BioLogos president Darrel Falk.

In Part 2 of this series, we concluded by noting that, as Christian geologists willing to consider the possibility, we find no compelling evidence that the earth’s geological features can be explained by a global Flood. Here we consider three lines of evidence: global salt deposits, the order of deposition of sediment layers in the Grand Canyon, and the sequence of fossils in geological strata.

Salt Deposits

There are many places around the earth with layers of salt, some thousands of feet in thickness. Just off the southern coast of the United States in the Gulf of Mexico, thick salt deposits sit beneath thousands of feet of sediment (Fig. 1). These deposits lie within the layers that are said to have been deposited by the Flood.

We understand how salt beds form. At locations such as the Bonneville Salt Flats of Utah, or at the Dead Sea at the border of Israel and Jordan, salt is actively forming. Salt beds form when water is evaporated. During evaporation, the concentration of dissolved ions increases until the water cannot hold the salt in solution anymore and mineral salt begins to form. If a presently unknown or poorly understood process could produce salt without evaporation, as argued by young-earth advocates¹, it would quickly dissolve as soon as it came into contact with flood water, just as the salt from your saltshaker rapidly dissolves when added to water or moist food.

One might argue that the waters from the Flood could have evaporated to leave behind the salt deposits we see today, but there is a serious problem. The thousands of feet of sediment on top of the salt is also said to be from the Flood, meaning the flood waters cannot have evaporated to produce the salt and still be present and violent enough to transport thousands of feet of sediment to the same location. In other words, a single flood cannot be called upon to explain both the salt and the overlying sediment. For those who wish to argue that natural processes could have been vastly different during the Flood, there are at least two replies. First, under such a scenario, there is no point in Flood Geology studies any more than in normal studies, for nothing could be gained by the study of unknowable processes. A more important question, however, would be to ask why God would alter natural processes just to make Flood sediments look like they are not flood sediments. What would the purpose be? (We will revisit this thought later.)

Grand Canyon: Order of Deposition

The Grand Canyon is made up of a sequence of layers that defies any reasonable attempt to explain by a single flood. The alternating layers of limestone, sandstone and shale each form in unique environments. If these deposits were formed at different times under various sea-level stages, it is quite simple to explain the different grain sizes and rock types as a function of depth and distance from the shore line. If explained with a single catastrophic flood that abided by God’s natural laws of physics and chemistry, logic must be stretched beyond the breaking point.

As a very simple observation, consider instructions given in virtually every gardening book. A good soil will have a mix of sand, silt and clay. To determine the quality of your soil, you take a handful or two, put it in a clear container, add water and shake it up. When you stop shaking, the coarse grained material will settle out first resulting in a sequence of layers: sand on the bottom, then silt, then clay. You can readily see how much of each you have by the thickness of each layer.

This is informative of what we see in flood deposits. As moving flood waters slow down, finer and finer grained sediment settles out resulting in a “fining upward” sequence. If most of the Grand Canyon layers were laid down by the Flood, then we should see the same thing – a “fining upward” sequence. Instead, we see a series of alternating layers of fine and coarse grained material, with smaller-scale alternating layers within the larger ones (Fig. 2). Increasing the violence of a flood does nothing to negate the standard order of deposition. Repeated surging of flood waters across the surface likewise offers little explanatory power; in this case we might expect successive layers, each with their own “fining upward” sequence, but such is not what is observed. Further, the Grand Canyon includes multiple layers of limestone, which are never found in flood deposits of any magnitude. Even in floods as massive as one thought to have catastrophically deluged the once dry Mediterranean Sea basin with thousands of feet of water – limestone beds are conspicuously absent.

Fossil Sequence

If a massive flood were responsible for the fossil record, what would we expect to see? If the Flood was violent enough to rip chunks of rock up from the earth and move entire continents (standard Young Earth claims)², then it should be obvious that life forms from every imaginable niche would be tumbled and mixed together (Fig. 3a). We should find numerous examples of mammoths mixed with triceratops, and pterodactyls mixed with sparrows. Ferns and meadow flowers should be found in the same deposits, along with trilobites and whales. Further, we should find all major life forms still living today, for Genesis 7:8-9 is clear in stating that all terrestrial animals were preserved on the ark.

What we actually observe is far different (Fig. 3b). There is an orderly sequence where trilobites only occur in very old rocks, dinosaurs in later beds, and mammoths in still later layers. Organisms like flowers and ferns are present together in more recent deposits, but only ferns with no flowers are found in older deposits. Some readers will recognize this as an example from the “geologic column” and be tempted to discount it as a fabrication. For those thinking this way, consider what Henry Morris had to say in both editions of Scientific Creationism:

“Creationists do not question the general validity of the geologic column, however, at least as an indicator of the usual order of deposition of the fossils…”⁵

If we revisit the Grand Canyon for a moment, is it not striking that there is not a single dinosaur, mammoth or bird in the entire exposed sequence? Not one. To find these, you have to go to younger sediments found in deposits outside the canyon that have not been fully eroded away yet. How could such a lack of mixing be possible if the Flood was violent enough to move continents?

For more, be sure to read our FAQs How are the ages of the Earth and universe calculated? and What scientific evidence do we have about the first humans?, as well as our recent infographic How Do We Know the Earth is Old?.

Author's Note from Joy Walters

As I mentioned in my first post, I grew up skeptical of the whole idea of evolution. One contributor to my disbelief was the lengthy timescale for the “tree of life” that was presented with the theory. I would hear, for example, that dinosaurs lived hundreds of millions of years ago, but there was no explanation of why this was true; it was just given as a fact. No one explained the methods of dating, and so I thought biologists simply estimated the ages of species to fit their preconceived notions of how long it would take for one species to emerge from another. It also seemed like the ages were periodically revised and extended farther back in time, and I figured scientists needed to manipulate numbers to make evolution plausible. This, in my mind, made the theory both unbelievable and dismissible.

Once I learned about the techniques used to date fossils, I realized that my first impressions were wrong; the ancient ages of species are scientific determinations rather than scholarly conjectures. However, I have found in recent conversations that Christians remain skeptical of old ages and the evolutionary time scale. For this reason, I wanted the videocast to address the process of fossil dating (what the methods are and why they are accurate) while focusing on cases where hominid fossils were discovered and dated using these very methods. My hope is that Believers would be informed about the evidence for human evolution and its scientific grounding.

(Click image for full resolution)

In a Nutshell

In Detail

Introduction

Astronomers and geologists have determined that the universe and Earth are billions of years old. This conclusion is not based on just one measurement or one calculation, but on many types of evidence. Here we will describe just two types of evidence for an old Earth and two types of evidence for an old universe; more types can be found under Further Reading. These methods are largely independent of each other, based on separate observations and arguments, yet all point to a history much longer than 10,000 years. As Christians, we believe that God created the world and that the world declares his glory, so we can’t ignore what nature is telling us about its history.

Age of the Earth from seasonal rings and layers

If you’ve ever seen a horizontal slice of a tree trunk, you’ve seen how a tree forms a new growth ring each year. In years of drought, the tree grows less quickly so the ring is narrower; in good growing seasons the ring is thicker. A tree’s age can be found by simply counting its rings. By comparing the pattern of thick and thin rings to weather records, scientists can verify that the method is accurate. This method can even be used on dead trees that fell in a forest long ago. For example, the last 200 rings in the dead tree might match up with 200 rings early in the life of the living tree, so the two trees together can count back many years. In this way, multiple trees can be used to build a master chronology for a forested region. European oak trees have been used to build a 12,000-year chronology.¹

The annual ice layers in glaciers provide a similar method that goes back much further in history. Each year, snowfall varies throughout the seasons and an annual layer is formed. Like the tree rings, this method can be verified by comparison to historical records for weather, as well as to records of volcanic eruptions around the globe that left thin dust layers on the glaciers. Scientists have drilled ice cores deep into glaciers and found ice that is 123,000 years old in Greenland² and 740,000 years old in Antarctica.³ These annual layers go back much farther than the 10,000 years advocated by the young earth creationists. The Earth must be at least 740,000 years old.

How can an old Earth be reconciled with Genesis? See Scripture Interpretation

Age of the Earth and solar system from radiometric dating

In your high school science classroom, you may have seen a large poster of the periodic table hanging on the wall. The periodic table shows the types of atoms that make up the world around us. An element in the periodic table can come in different flavors called isotopes. Some isotopes are unstable, and over time these isotopes “decay” into isotopes of other elements. For example, Potassium-40 is unstable and decays into Argon-40. As time passes, a rock will have more and more Argon-40 and less and less Potassium-40. Radiometric dating is possible because this decay occurs at a known rate, called the “half-life” of the radioactive element. The half-life is the time that it takes for half the radioactive sample to change from one element into the other.

Some isotopes have short half-lives of minutes or years, but Potassium-40 has a half-life of 1.3 billion years. Radiometric dating requires that one understand the initial ratio of the two elements in a given sample by some means. In this case, Argon-40 is a gas that easily bubbles out and escapes when it is produced in molten rock. Once the rock hardens, however, all the Argon-40 is trapped in the sample, giving us an accurate record of how much Potassium-40 has decayed since that time. So, if we find a rock with equal parts Potassium-40 and Argon-40, we know that half the Potassium-40 has decayed into Argon-40, and that the rock hardened 1.3 billion years ago.⁴

It’s hard to find rocks on the surface of the Earth that have not been altered over time. Most old rocks have been eroded by wind and water or submerged by continental plates. The oldest reliably dated rock formation is in Greenland, where several different isotopes were used to find an age of 3.6 billion years.⁵ Scientists also recently dated zircon grains (which resist erosion) in Western Australia to 4.4 billion years old.⁶ To find older rocks that haven’t been eroded, we need to look beyond Earth. Meteorites are rocks from the solar system that have fallen to Earth recently and haven’t suffered much erosion. Their pristine interiors give an age that dates back to their formation at the beginning of the solar system. Nearly all meteorites have the same radiometric age, 4.56 billion years old.⁷ Thus, the solar system, including the Earth, is about 4,560,000,000 years old.

PLEASE READ THE REST OF THE ANSWER HERE.

Notes

1. Davis A. Young, ”How Old Is It? How Do We Know? A Review of Dating Methods – Part One: Relative Dating, Absolute Dating, and Non-radiometric Dating” Perspectives on Science and Christian Faith, Vol 58 No 4 (2006), p. 264. (PDF)
2. Roger C. Weins, "Radiometric Dating: A Christian Perspective", The American Scientific Affiliation (2002). See also North Greenland Ice Core Project Members, “High-resolution Record of Northern Hemisphere Climate Extending into the Last Interglacial Period,” Nature 431 (2004): 147–151, which reports ages back to 123,000 years. (web article)
3. EPICA Community Members, “Eight Glacial Cycles from an Antarctic Ice Core,” Nature 429 (2004): 623–628.
4. Young earth creationists reject radiometric dating methods, including claims that decay rates are not constant. For a critical review, see Randall Isaac “Assessing the RATE Project”, Perspectives on Science and Christian Faith, vol 59, no 2, June 2007, p.143-146. (PDF)
5. See Wiens and references therein. (web article)
6. Wilde et al. “Evidence from detrital zircons for the existence of continental crust and oceans on the earth 4.4 Gyr ago,” Nature (2001) 409, 175-178.
7. See Davis A Young, ”How Old Is It? How Do We Know? A Review of Dating Methods—Part Two: Radiometric Dating: Mineral, Isochron and Concordia Methods” Perspectives on Science and Christian Faith, Vol 59, No 1 (2007) and references therein (PDF)
]]> Sat, 14 Jul 12 05:02:55 -0700 http://biologos.org/blog/the-fossil-record?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/the-fossil-record?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication 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. The Fossil Record: Is there enough evidence ?

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.

A more expanded discussion of this topic can be found in Miller, K.B., 2003, “Common descent, transitional forms, and the fossil record,” IN, K.B. Miller (ed.), Perspectives on an Evolving Crreation, Wm. B. Eerdmans, Grand Rapids.

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.

]]> Fri, 13 Jul 12 05:00:15 -0700 Keith Miller http://biologos.org/questions/what-scientific-evidence-do-we-have-about-the-first-humans?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/questions/what-scientific-evidence-do-we-have-about-the-first-humans?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication In recent decades, scientists have discovered more about the beginnings of humanity. The fossil record shows a gradual transition over 5 million years ago from chimpanzee-size creatures to hominids with larger brains who walked on two legs. Later hominids used fire and stone tools and had brains as large as modern humans. Fossils of homo sapiens in east Africa date back nearly 200,000 years. Humans developed hearths for fire, stone points for spears and arrows, and cave paintings by 30,000 years ago. By 10,000 years ago, humans had spread throughout the globe. Genetic studies support the same picture. Humans share more DNA with chimpanzees than with any other animal, suggesting that humans and chimps share a relatively recent common ancestor. Also, the same defective genes appear in both humans and chimps, at the same locations in the genome—an observation difficult to explain except by common ancestry. Genetics also tells us that the human population today descended from more than two people. Evolution happens not to individuals but to populations, and the amount of genetic diversity in the gene pool today suggests that the human population was never smaller than several thousand individuals. Yet all humans, of all races, are descended from this group. Humanity is one family. Coming Soon]]> Thu, 12 Jul 12 14:34:24 -0700 http://biologos.org/blog/evolutionary-convergence?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/evolutionary-convergence?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication In today's video, Oxford physicist Ard Louis discusses the famous debate between renowned evolutionary biologists Stephen Jay Gould and Simon Conway Morris over the idea of evolutionary convergence.

Today's video is courtesy of filmmaker Ryan Pettey, director/editor of Satellite Pictures and features physicist Ard Louis.

In today's video, Oxford physicist Ard Louis discusses the famous debate between renowned evolutionary biologists Stephen Jay Gould and Simon Conway Morris. Gould believed (and wrote in his book Wonderful Life) that if the "tape" of evolution were rerun, the chance that anything like human intelligence would emerge is essentially zero. In other words, humanity is here through random accident. Gould pointed to the work of Morris and fellow scientists in their research of the Burgess Shale as evidence for this view.

However, Morris himself disagrees, pointing to what is called evolutionary convergence. As Morris notes, there are numerous examples of identical features evolving multiple times throughout the history of life independently. Morris believes that if the tape of life were replayed, we would see something like humans emerge. A Christian might say, it looks like we were planned.

Some Christians might find Simon Conway Morris' viewpoint, with its implicit teleology, more attractive. Others, perhaps motivated by a high view of providence, may find Gould's emphasis on contingency equally congenial to their faith. What do you think?

]]> Thu, 15 Dec 11 05:51:27 -0800 Ard Louis http://biologos.org/blog/series/evidences-for-evolution?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/series/evidences-for-evolution?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication This technical series, co-written by Darrel Falk and David Kerk, looks into the evidence for evolution in order to dispel doubts that people may have about this well-supported theory. They look at three things specifically: the separate methods which reveal of the age of the earth, the unfolding history of whale evolution, and finally the common trends of heart development in vertebrates. A literalistic view of Genesis causes many evangelicals to believe that the earth is less than ten thousand years old. Christian children and young people frequently grow up being told that the earth is young and that evolution is a lie. The most popular science/religion web-site by far according to Alexa ratings is “Answers in Genesis”, and its museum, dedicated to a young earth perspective has attracted over 1 million visitors since its opening two years ago. Since evangelicals, we believe, are correct about so many other all-important issues, how can we be so certain that so many are so wrong about this one? Consider sending this link to a young earth friend or pastor. Some think that the science behind this matter can’t be trusted. Nothing could be further than the truth.

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.

]]> Sun, 27 Nov 11 23:31:20 -0800 David Kerk, Falk, Darrel http://biologos.org/blog/centered-the-language-of-science-and-faith?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/centered-the-language-of-science-and-faith?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication In a recent interview with the Sirius XM radio show Centered, Karl Giberson sat down with host Don Belanus to discuss the book The Language of Science and Faith.

In a recent interview with the Sirius XM radio show Centered, Karl Giberson, co-author of BioLogos' The Language of Science and Faith, sat down with host Don Belanus to discuss the book and the interplay between science and faith. Among the topics they cover are what constitute the "genuine questions" of science and faith mentioned in the title and whether the age of the earth should be a top priority for pastors to discuss with their congregations.

]]> Fri, 18 Nov 11 05:56:02 -0800 Karl Giberson http://biologos.org/blog/surrogate-arguments?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/surrogate-arguments?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication In this video, Brian McLaren discusses the idea of surrogate arguments, in which a debate over one thing is really a means for arguing something completely different. According to McClaren, the argument over the age of the earth is one such argument.

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

In this video, author and pastor Brian McLaren discusses the idea of surrogate arguments, in which a debate over one thing is really a means for arguing something completely different. According to McClaren, the argument over the age of the earth is one such example, in which an apparent scientific debate is actually a discussion over the nature of religious authority and how previous generations have understood how we should interpret the Bible. Such debates can lead to two crises: one of confidence and one of ethics. While some have the confidence to differ with the views of the generation that raised them in the faith, McLaren points out that some are not able to overcome the ethical challenge of differing with grace and love. When this happens, he notes, the end result is damage to the Church and a retrenching of the views of the older generation. Managing the crises well requires courage of convictions while also respecting tradition and maintaining a gracious spirit. Anything less, is not only unwise, it is also unfaithful.

]]> Wed, 21 Sep 11 09:11:52 -0700 Brian McLaren http://biologos.org/blog/new-limbs-from-old-fins-part-2?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/new-limbs-from-old-fins-part-2?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication Critics of evolution sometimes portray the theory as an untestable historical conjecture, depicting it as fundamentally different from experimental science in the lab. But the hunt for the earliest tetrapods was an effort to test a hypothesis that had generated a prediction. In the previous post in this series, we looked at the remarkable blueprint that underlies all limbs – one bone, two bones, blobs, digits – and considered some ways we might explain it. One potential explanation is, roughly speaking, design. Perhaps the blueprint represents an idea or preference in the mind of the Creator. Perhaps the blueprint represents an optimized design, one so superior that there is no better way to build a limb. The other potential explanation is common ancestry. The blueprint was present in ancestors of the distant past, and it has been retained with modification in all tetrapod vertebrates that have descended from those pioneering ancestors. We noted that one explanation need not entirely preclude the other.

In the rest of the series, we will look closely at the evolutionary explanation for the blueprint. That explanation postulates that tetrapod limbs arose during a particular era in life's history, and that they arose as modifications of the fins of fish. And the evolutionary explanation isn't just an interesting idea. It's a comprehensive explanation – it helps us to understand bones, fossils, genes, chemical signaling systems. It provides a coherent framework for understanding why limbs are the way they are, and how they got that way.

Comparing the anatomy of tetrapod vertebrates and fish

The idea that tetrapods arose from fish is not new; E.D. Cope proposed in 1892 that tetrapods descended from lobe-finned fish. (Modern lobe-finned fishes include coelacanths and lungfish, and comprise one of two divisions of the bony fishes. The other division, the ray-finned fishes, includes most familiar kinds of fish.) In the early days, biologists inferred ancestral relationships between species largely through comparative anatomy and embryology: they would carefully classify organisms according to their structure (including their structure during development) and look for relationships that generated nested hierarchies. A simple nested hierarchy goes something like this: 1) animals with backbones; 2) animals with backbones and limbs; and 3) animals with backbones, limbs, and hair. Animals in group 3 also belong to groups 1 and 2, while animals in group 2 also belong to group 1, and so the groups together define a nested hierarchy. Such studies alone could have led some scientists to infer an ancestral relationship between fish and tetrapods, and perhaps those studies did convince them. But then there were fossils of various types of fish and other vertebrates, many long extinct. That fossil record was relatively sketchy in 1892, but it nevertheless led Cope and others to conclude that certain fish had given rise to tetrapods at a particular time in natural history.

The fossil record shows a fish-to-tetrapod transition

Here are some basic findings from the fossil record that suggest a fish-to-tetrapod transition and that have been known for decades:

• Fish, including fish with bones, lived on the earth before tetrapods appeared. Specifically, fossils of bony fish first appear in rocks from about 420 million years ago.

• Tetrapods appear in the fossil record at a particular point in history and then persist and diversify in subsequent eons. Their arrival was long thought to have occurred about 365 million years ago, although some recent findings have challenged that hypothesis.

• Tetrapods that still had some fishy features were prowling the planet 365 million years ago.

• Lobe-finned fish that were starting to look more like tetrapods were eating other fish about 385 million years ago.

Even many decades ago, there were hints that something interesting happened between 400 million years ago and 365 million years ago. Let's take a close look at the ancient animals that suggest the fish-to-tetrapod transition.

Ancient animals

The most primitive known tetrapods for which we have skeletal remains lived 365 million years ago. They were undeniably tetrapods, but there was definitely something fishy about them. (Heh heh.) One of the most famous of these creatures is Acanthostega, discovered in 1987 by British paleontologist Jennifer Clack and pictured below. Acanthostega is a card-carrying tetrapod, with fingers and toes. But it has a fish tail, with fin rays. Another well-known primitive tetrapod is Ichthyostega, which lived around the same time as Acanthostega. Like Acanthostega, it is a true tetrapod, but has several odd fish-like structural features. For example, its skull is more fish-like than that of Acanthostega. In summary, both Acanthostega and Ichthyostega already used the limb blueprint, even though both also had some fish-like anatomical characteristics. Their presence 365 million years ago shows that tetrapods must be at least that old, and their mixture of anatomical features suggests that the transition happened not long before that.



And what about the lobe-finned fish that looked a bit tetrapod-ish? That animal is Panderichthys, described as “vaguely crocodile-shaped” with skeletal features that were tetrapod-like. Specifically, this ancient fish had tetrapod-like “shoulders,” and recent analysis found some finger-like bones at the ends of the fins. The creature also had a breathing hole on the top of its head. These fish lived around 385 million years ago.

The hunt for the earliest tetrapods

Taken together, these observations suggested that the fish-to-tetrapod transition occurred between 385 and 365 million years ago. Eager to see what that transition looked like, scientists began to look for 375 million-year-old rocks in which they might find animals at the beginning of tetrapod-hood. They wanted to catch evolution in the act.

Let's stop and think about this, because it's cool and because it's important to note the extent to which evolutionary biology is hypothesis-driven. Critics of evolution sometimes portray the theory as an untestable historical conjecture, depicting it as fundamentally different from experimental science in the lab. But the hunt for the earliest tetrapods was an effort to test a hypothesis that had generated a prediction. Based on the hypothesis that lobe-finned fish were ancestors of tetrapods, scientists predicted that intermediate animals, “fishapods,” would be found in the gap between Panderichthys and Acanthostega. To evaluate the prediction, all they needed to do was find some suitable 375 million-year-old rocks.

Neil Shubin describes that search in the first chapter of Your Inner Fish. He and his colleagues found suitable rocks in the islands of the Arctic: the right age, nicely exposed (by erosion), and representative of the kind of environment that their quarry would frequent – freshwater streams. They made their biggest discovery on their last trip (“a do-or-die situation”) in 2004. That discovery was Tiktaalik roseae, the “fishapod.”

The “fishapod”

Tiktaalik roseae is one of the most extraordinary fossil intermediates ever described, and its public debut in 2006 was front-page news. An artist's conception of the animal is pictured below.



There are several aspects of the anatomy of Tiktaalik that earn it the title “fishapod.” Like a good fish, it had scales and webbed fins. Like a tetrapod (more specifically, like a crocodile), it had a flat head, with eyes on the top of the head, and it had a neck. But what about those fins? Or are they limbs? Remarkably, the answer seems to be, “both.”

The fins of Tiktaalik were part fish fin, part tetrapod limb. On the outside, they looked like fins, with webbing. On the inside, though, these fins were clearly tetrapod-like. Amazingly, the fins of Tiktaalik were built using a primitive version of the limb blueprint: one bone, two bones, blobs, digits. As Shubin writes in Your Inner Fish, “We had a fish with a wrist.” (The Tiktaalik roseae web site at the University of Chicago is a great source for images and more information.)

Let's address three questions about Tiktaalik that might have occurred to you. First, why might animals like Tiktaalik have developed tetrapod-like fins? Shubin and his colleagues suggest that these limb-like fins may have been useful for doing “push-ups” in the shallow water. (Like Panderichthys, Tiktaalik had a breathing hole on top of its head and was clearly adapted for living and moving in shallow water.) Second, is Tiktaalik an ancestor of all tetrapods? No, not necessarily. What Tiktaalik shows us is that animals were developing tetrapod features in the context of fish bodies, and Tiktaalik shows us the context (shallow water) in which this likely occurred. But that doesn't mean that our lineage arose from Tiktaalik itself. Finally, is Tiktaalik now the oldest tetrapod? No, apparently not. For one thing, Tiktaalik is truly transitional, and probably therefore not worthy of full tetrapod membership. But more notably, data published in 2010 show that tetrapods are a lot older than was thought at the time of Tiktaalik's discovery. The new findings show footprints that are unmistakably those of a tetrapod, in rocks about 395 million years old. Surprisingly, then, tetrapods were already on their way long before Neil Shubin's specimen lived. Tiktaalik is truly a fish/tetrapod intermediate, which was living at the same time as animals that were fully tetrapods. A simple story of succession, in which intermediates disappear and are replaced by less intermediate types, seems to be an oversimplification.

In conclusion, the fossil record provides evidence that the fins of fish and the limbs of tetrapods are related by ancestry: limbs seem to be modified versions of fins. What other evidence supports this proposal? In the next post, we will turn to developmental biology, and explore the meaning of the term 'homology.'

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.

Carl Zimmer (2006) A Fin is a Limb is a Wing: How Evolution Fashioned its Masterworks. Online at NationalGeographic.com.

Tiktaalik roseae website at the University of Chicago.

Jennifer Clack's website at the University of Cambridge.

Images are from Wikipedia.

]]> Fri, 16 Sep 11 04:59:54 -0700 Stephen Matheson http://biologos.org/blog/gods-use-of-time?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/gods-use-of-time?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication I find that when many Christians think about the way God created our universe, they often bring a static expectation similar to what we bring to an ordinary statue. It’s as if we assume the physical realm were merely a rigid three-dimensional sculpture, immovable with time. I can still recall the first time I encountered a man performing as a living statue. His costume, body paint, and utter stillness made him very convincing. I also recall the eerie feeling I experienced upon first seeing him move. Ordinary statues are, of course, static, but if you hang around a living statue long enough you’re bound to see it move, if only to blink its eyes. I find that when many Christians think about the way God created our universe, our planet, and the forms of life that dwell on it, they often bring a static expectation similar to what we bring to an ordinary statue. It’s as if we assume the physical realm were merely a rigid three-dimensional sculpture, immovable with time.

But since time exists, change and development are possible. The sciences have acquired the tools to “look back” in time and explore our universe’s rich history, so we know that the universe and the life in it do indeed evolve. Through these observations in the natural realm, it’s difficult to avoid the conclusion that God typically prefers to do His work gradually rather than instantaneously. In what follows, I’d like to briefly explore some of the ways that our universe has been and is evolving over long periods of time and attempt to show that the concept of a God who makes use of long timescales ought to be familiar to us from the story of redemption in scripture. And like observing a living statue, by staring long enough (in this case millions and billions of years) we are able to see a world that is moving and changing, which hopefully deepens our appreciation for the wonder of God’s dynamic creative acts.

God’s use of time in the physical realm

The sense of enjoyment that comes from studying the dynamically evolving universe that God has created is similar to that of a gardener when he or she watches a seed grow into a mature plant. And when considering the history of the cosmos, the analogy of a seed in a garden is an apt one, with each branch of science reinforcing and corroborating the story that is told.

From physics we learn that all the matter and energy that now exists in our universe originated in a hot, dense state (something akin to a primordial seed) which burst forth and has been expanding and cooling ever since. Myriads of stars have gone through the process of forming, burning, and dying, with many exploding in what's called a supernova. These long stellar life cycles have been going on for billions of years and are responsible for "cooking up" and dispersing all the atomic elements necessary for forming planets like Earth and creatures like us.

Once our planet formed, we know from geology and its theory of plate tectonics that the earth's crust has been in a constant (but very slow) process of moving and changing, shifting even the continents around over many millions of years and forming majestic mountains, islands, and other geological features. The picture becomes even more fascinating when biology enters the landscape, describing how life has slowly developed, also over many millions of years, beginning from the simplest of organisms and progressing all the way to beings like us, of such complexity that we are able to reflect on and enjoy the entire display.

But how do we know all this, since our short lives don’t allow us to see these long drawn out processes in action? I see these same sciences as a great gift from God that allow us to explore beyond the bounds of our own time. For instance, when astrophysicists look up into the night sky, they see light that has taken millions or even billions of years to reach us, meaning that they are literally looking at what our universe looked like in the distant past. Geologists look back in time by studying layers of rock, sediment, or ice. They have even found evidence that the earth's magnetic field has flipped many times over the course of the Earth's history so that even the direction our trusty compasses point isn’t constant! Biologists have the fossil record and genetics as a means of exploring the rich and fascinating history of life, teaching us about the ancestors of modern humans as well as exotic creatures such as dinosaurs. All around us the physical world is shifting, changing, and unfolding in an extraordinary way, teaching us that God, the ultimate Gardener, is pleased to watch his creation grow and mature gradually.

God's use of time in redemption up to Jesus

A good number of Christians find the idea of God using long maturation times in creation threatening to their understanding of scripture. But what we learn about God from scripture is not inconsistent with a God who works over long timescales. We see this if we look at the grand meta-narrative of the entire Bible, of which I’ll cover a few highlights to demonstrate my point.

After humans made a mess of their intended role in the created order, God desired to restore it and put it right. And like what we learn from the sciences about the evolution of the universe, He decided to take his time about it. God began his redeeming work with a promise to use Abraham's family to be a blessing to the entire world (Gen. 12:1). This was a promise that was ultimately fulfilled in Jesus nearly two millennia later. Now if God had been in a hurry, he might simply have allowed Sarah to conceive by the Holy Spirit and bring forth Jesus directly. But instead, he decided to take the scenic route, working through Abraham’s seed, including Jacob, Moses, David, and others until the time was right for Jesus.

As time went on and God’s people developed into a nation, David rose to the throne and God made another promise -- that of perpetual kingship to David’s line (2 Sam 7:13). This was another opportune time for Jesus to be born, take the throne, and fulfill the promise. But again we find God taking his time, allowing the kingdom to be divided and eventually conquered, and God’s people sent into a long exile, until the time was right for Jesus, nearly a millennium after David.

God's use of time in redemption after Jesus

The Christian faith holds that in the “fullness of time” (Gal. 4:4) God sent Jesus as the individual in whom all the promises of God ultimately converged. Just as God's physical creation developed slowly and eventually brought forth our earth and life and humanity, so God's purposes slowly unfold and culminate in Jesus, the descendant of Abraham and David who becomes the blessing to the world.

But here again is another case that demonstrates the point I’m attempting to make. Even the blessing that Jesus comes to announce and inaugurate develops slowly and dynamically – God, the Gardener, continues to slowly cultivate. Jesus himself teaches us to expect this to be the case in parables about the kingdom such as that of the mustard seed (Mark 4:30-32). Thus, the world isn’t automatically cured of its ills after Jesus’ resurrection. Both then and now, evil, sin, and injustice still exist and there is much that remains to be redeemed. The church is called to continue living in this meta-narrative until we reach the second climax: when Jesus reappears and ushers in the fullness of the new heavens and new earth.

A similar point can be made about God’s redemptive work in the lives of individual Christians as well. God forms each of his children over time through our relationships, our experiences, the trials we encounter, and the service we render. “I am the vine, you are the branches”, says Jesus in John 15:5. God is “growing us” as individuals and as every Christian knows from experience, the maturing process often seems very long indeed.

In conclusion, this brief survey has shown a consistent picture of how God works in his creation. In the cosmos, in the evolution of life, in the redemption of the world, and in the redemption of individuals, God sees fit to use long timescales for accomplishing his purposes. Moreover, with the similarities between what we learn of God from nature and from scripture, Christians needn’t react defensively to what science tells us about the history of the cosmos. Instead, we can indulge in the opportunity to marvel at the ever continuing work of God the Gardener, both in His dynamic creation and His dynamic acts of redemption.

Photo courtesy of Flickr user ToniVC.

]]> Fri, 19 Aug 11 05:00:43 -0700 Matthew Blackston http://biologos.org/essays/the-cambrian-explosion-transitional-forms-and-the-tree-of-life?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/essays/the-cambrian-explosion-transitional-forms-and-the-tree-of-life?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication Geologist Keith Miller examines the "Cambrian Explosion", a period of rapid evolutionary diversification approximately 575 million years ago, and whether it poses a challenge to evolutionary theory. Mon, 02 May 11 18:45:49 -0700 Keith Miller http://biologos.org/blog/series/cambrian-series?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/series/cambrian-series?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication Many evolutionary critics have identified the Cambrian Explosion as a stumbling block to the theory of evolution, arguing that the “expected transitions between major invertebrate phyla are absent, and that the suddenness of their appearance in the fossil record demonstrates that evolutionary explanations are not viable.” Keith Miller argues that the Cambrian Explosion is not so problematic as these opponents claim after all. This is part one in a series by Keith Miller. It is an updated and extension of Miller and Campbell's 2003 essay “The ‘Cambrian explosion’: A challenge to evolutionary theory?” from the book Perspectives on an Evolving Creation: Grand Rapids, and it coincides with our Question, "Does the Cambrian Explosion pose a challenge to evolution?". A pdf version of Miller's full paper can be found here.

Introduction: What’s all the fuss?

The most fundamental claim of biological evolution is that all living organisms represent the outer tips of a diversifying, upward-branching tree of life (click image to enlarge). The “tree of life” is an extremely powerful metaphor that captures the essence of evolution. Like the branches of a tree, as we trace individual lines of descent (lineages) back into the past (down the tree) they converge with other lineages toward their common ancestors. Similarly, these ancient lineages themselves converge with others back in time. Thus, all organisms, both living and extinct, are ultimately connected by an unbroken chain of descent with modification to a common ancestral trunk among single-celled organisms in the distant past.

This tree metaphor applies as much to the emergence of the first representatives of the major groups of living invertebrates (such as annelids, snails, or arthropods) as it does to the first appearance and diversification of dinosaurs, birds, or mammals. This early diversification of invertebrates apparently occurred around the time of the Precambrian/Cambrian boundary over a time interval of a few tens of millions of years. This period of rapid evolutionary diversification has been called the “Cambrian Explosion.”

The Cambrian explosion has been the focus of extensive scientific study, discussion, and debate for decades, and is increasingly receiving attention in the popular media. It has also received considerable recent attention by evolution critics as posing challenges to evolution. These critics argue that the expected transitions between major invertebrate groups (phyla) are absent, and that the suddenness of their appearance in the fossil record demonstrates that evolutionary explanations are not viable.

What are some of the arguments of the evolution critics? John Morris of the ICR writes:

“If evolution is correct, the first life was quite simple, evolving more complexity over time. Yet the Cambrian Explosion of Life has revealed life's complexity from the start, giving evolution a black eye. The vast array of complex life that appears in the lowest (or oldest) stratigraphic layer of rock, with no apparent ancestors, goes hard against evolutionary dogma. Evolution's desperate attempt to fill this gap with more simple ancestral fossils has added more injury. .... Think of the magnitude of this problem from an evolutionary perspective. Many and varied forms of complex multi-celled life suddenly sprang into existence without any trace of less complex predecessors. There are numerous single-celled forms at lower stratigraphic levels, but these offer scant help in solving the mystery. Not one basic type or phyla of marine invertebrate is supported by an ancestral line between single-celled life and the participants in the Cambrian Explosion, nor are the basic phyla related to one another. How did evolution ever get started?”¹

Intelligent design advocate Stephen Meyer and others have written:

“To say that the fauna of the Cambrian period appeared in a geologically sudden manner also implies the absence of clear transitional intermediates connecting the complex Cambrian animals with those simpler living forms found in lower strata. Indeed, in almost all cases, the body plans and structures present in Cambrian period animals have no clear morphological antecedents in earlier strata.²

And:

“A third feature of the Cambrian explosion (as well as the subsequent fossil record) bears mentioning. The major body plans that arise in the Cambrian period exhibit considerable morphological isolation from one another (or “disparity”) and then subsequent “stasis.” Though all Cambrian and subsequent animals fall clearly within one of a limited number of basic body plans, each of these body plans exhibits clear morphological differences (and thus disparity) from the others. The animal body plans (as represented in the fossil record) do not grade imperceptibly one into another, either at a specific time in geological history or over the course of geological history. Instead, the body plans of the animals characterizing the separate phyla maintain their distinctive morphological and organizational features and thus their isolation from one another, over time.”³

Are these critiques warranted? To what extent is the Cambrian explosion really problematic for the evolutionary picture of an unbroken tree of life extending back to the earliest life on Earth?

Geologic Time Scales: How big was the bang?

The relative rapidity of the diversification of invertebrates during the Cambrian “explosion” is set against the backdrop of the Earth’s geologic and biologic history. Geologic time is unfamiliar to most people, and its shear vastness is difficult to grasp.

Two lines of evidence impact our understanding of the duration of the animal diversification that led to the appearance of the major groups of living invertebrates. The first is the dating of critical strata within the geological timeline such as the Precambrian-Cambrian boundary and various important fossil-bearing horizons. The second is the time of appearance of the first widely recognized fossil representatives of the major living groups (phyla) of invertebrate animals. The latter is in considerable flux as new fossil discoveries are made.

Originally, the base of the Cambrian had been set at the earliest appearance of organisms with mineralized skeletons - particularly trilobites. However, a diverse collection of tiny mineralized plates, tubes and scales was discovered to lie below the earliest trilobites.⁴ This interval of “small shelly fossils” was designated the Tommotian. Because of the presence of even earlier tiny mineralized tubes and simple burrows, there was no internationally accepted definition for the boundary until 1994. At that time, the base of the Cambrian was placed at the first appearance of a particular collection of small fossil burrows characterized by Treptichnus pedum.



Until the early 1990's the age of the Precambrian-Cambrian boundary was not tightly constrained, and was estimated to be about 575 million years ago. However, in 1993 new radiometric dates from close to the accepted Precambrian-Cambrian boundary revealed that it was significantly younger -- about 544 million years.⁵ A more precise date of 542 ± 0.3 million years has recently been formally accepted by the International Commission on Stratigraphy. The basis for this date was the discovery that a sharp worldwide fall (or negative spike) in the abundance of the isotope carbon-13 was coincident with the Cambrian boundary as previously defined. In Oman, this isotopic marker also coincides with a volcanic ash layer that yielded the 542 million year date using uranium/lead radiometric methods.⁶ This horizon also marks the last occurrence of several fossils characteristic of the underling late Precambrian Ediacaran Period.⁷ Such extinction events are commonly used to subdivide the geologic time scale.

The earliest diverse fossil invertebrate communities of the Cambrian are represented by the Chengjiang, in China. These deposits are dated at 525-520 million years. The famous Burgess Shale is considerably younger, dating at about 505 million years, and the end of the Cambrian Period is set at 490 million years. The Cambrian Period thus lasted for 52 million years. To put this in perspective, the time elapsed since the extinction of the dinosaurs at the end of the Cretaceous has been 65 million years. The Cambrian was a very long period of time.

If the Cambrian explosion is understood to comprise the time from the base of the Cambrian to the Chengjiang fossil beds, then this period of diversification in animal body plans appears to have lasted about 20 million years. However, not all living animal phyla with a fossil record first appear within this time window. The colonial skeleton-bearing bryozoans, (click for image) for example, are not known from the fossil record until the end of the Cambrian around 491 million years ago.⁸ More significantly, several living invertebrate phyla have a fossil record that extends into the late Neoproterozoic before the Cambrian. Sponges (click for image) have been recognized as early as 580 million years, cnidarians (click for image--the group includes jellyfish and anemones) are present among the Ediacaran animals at around 555 million years, and the stem groups (see discussion below) for some other phyla were also likely part of the Ediacaran communities.







Defining the Cambrian “explosion” is not as straightforward as it might seem. Although there was clearly a major burst of evolutionary innovation and diversification in the first 20 million years or so of the Cambrian, this was preceded by an extended period of about 40 million years during which metazoans (multicellular animals) arose and attained critical levels of anatomical complexity. The Ediacaran saw the appearance of organisms with the fundamental features that would characterize the later Cambrian organisms (such as three tissue layers, and bilaterally symmetric bodies with a mouth and anus), as well as the first representatives of modern phyla. The base of the Cambrian is not marked by a sharp dramatic appearance of living phyla without Precambrian roots. It is a subjectively defined point in a continuum. The Cambrian “explosion” appears to have had a “long fuse.”

Notes

1. Morris, J.D., 2008, The Burgess shale and complex life, Acts & Facts 37 (10): 13.
2. Meyer, S.C., M. Ross, P. Nelson, & P. Chien. 2003. The Cambrian explosion: biology's big bang. Pp. 323-402 in J. A. Campbell & S. C. Meyer, eds., Darwinism, Design and Public Education: Michigan State University Press, Lansing, p. 326.
3. Meyer, S.C., M. Ross, P. Nelson, & P. Chien. 2003. The Cambrian explosion: biology's big bang. Pp. 323-402 in J. A. Campbell & S. C. Meyer, eds., Darwinism, Design and Public Education: Michigan State University Press, Lansing, p. 333.
4. Rozanov, A.Y., 1984, “The Precambrian-Cambrian boundary in Siberia,” Episodes 7: 20-24. Rozanov, A.Y., and A.Y. Zhuravlev, 1992, “The Lower Cambrian fossil record of the Soviet Union,” IN J.H. Lipps and P.W. Signor (eds.), Origin and Early Evolution of the Metazoa: Plenum, New York, p.205-282.
5. Bowring, S.A,, J.P. Grotzinger, C.E. Isachsen, A.H. Knoll, S.M. Pelechaty, and P. Kolosov, 1993, “Calibrating rates of Early Cambrian evolution,” Science 261: 1293-1298.
6. Gradstein, F.M., J.G.Ogg, A.G. Smith, et. al., 2004. A Geologic Time Scale 2004. Cambridge University Press.
7. Amthor, J. E.; J.P. Grotzinger,; S. Schröder, S.A. Bowring, J. Ramezani, M.W. Martin, and A. Matter, 2003, "Extinction of Cloudina and Namacalathus at the Precambrian-Cambrian boundary in Oman". Geology 31: 431–434.
8. Landing, E., A. English,and J.D. Keppie, 2010, “Cambrian origin of all skeletonized metazoan phyla - Discovery of Earth’s oldest bryozoans (Upper Cambrian, southern Mexico),” Geology 38: 547-550.

]]> Fri, 11 Mar 11 08:00:11 -0800 Keith Miller http://biologos.org/blog/when-appearances-are-deceiving?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication http://biologos.org/blog/when-appearances-are-deceiving?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication “That just doesn’t sound right.” Ever since I was a kid, that was my gut reaction to those well-meaning people in my church and school who told me that despite what many in the sciences were saying, the earth and the entire universe were actually of relatively recent manufacture. “That just doesn’t sound right.”

At one time or another, we have all had this reaction to something someone said to us. Usually what we indicate by saying this is that we sense intuitively that something is amiss in what was just communicated to us but we cannot at the moment lay our finger on just what that “something” is.

Ever since I was a kid, that was my gut reaction to those well-meaning people in my church and school who told me that despite what many in the sciences were saying, the earth and the entire universe were actually of relatively recent manufacture (say, on the order of 10,000 years of age or so). Yes, there are rocks on the earth that test out to be millions of years old but you must understand: all of those things popped into existence in one fell swoop already bearing the marks of a certain age. God created the universe in motion with the appearance of age. It looks old but it isn’t. Already on his first night in Eden, Adam was able to see stars that we can now measure to be so far away that their light would take millions of years to get here. But because God created things already in motion, that light hit Adam’s eyeballs immediately even though the universe was a scant six days old.

That never sounded right to me, but one could conceive of it. Doing such a thing would hardly be beyond an almighty God’s abilities. God could snap his fingers and create any state of being he wanted. Still, something about the whole “appearance of age” scheme nettled. After all, what God could do cannot trump what a loving and true God would do.

My “Ah-Ha” moment that confirmed my intuition that something was wrong here came a few years ago when my colleague, Deborah Haarsma, gave a guest lecture in a theology and science course I was teaching. At one point Deb said to the class that we must remember that the light that streams to us from stars and galaxies and nebulae is not just generic light—these streams of light tell a story. They represent cosmic history. All of that light is the collective memory of the cosmos. It tells us about when stars were born. It tells us about when stars matured. It tells us about when stars died (and the stages they went through en route to their deaths). Light tells a story. It tells the story of the universe.

As a preacher, I have spent years training myself to think analogically. Those of us who preach for a living (and those of us who teach for a living) know that one of our main tasks is to take complicated doctrines, theories, or concepts and try to make them plainer and easier to understand by way of analogy. We are constantly saying, “Think of this idea this way . . . “ or “I know this portion of theology sounds difficult to grasp but what if you realize that it is actually a little like this . . .”

Deb’s helpful comment that beams of light tell the universe’s story finally helped me come up with the analogy that made me hit on the “something” that was wrong with this whole scheme. Ever since then, here is what I have told people in order to convey to them what I believe is wrong with the appearance of age argument.

Saying the universe was created in motion is sort of like this: imagine you are like me, a guy who will turn 47 years of age in March of 2011. As a 47-year-old person, I have almost five decades of memories. I can remember my brother being born when I was four years old. I can remember my mother walking me to kindergarten, my family moving to a new area when I was half-way through second grade, graduating from high school, traveling to Europe for the first time, meeting my wife, and the births of my two children. This memory stream, this history of my life that appears to me in my mind, is clear and vivid and undeniable. There is nothing inside of me or in the ways I retrieve these images to tell me they are anything other than iron-clad truth. This is what has happened to me along the way. This is my story. I’ve even got pictures and videos of all those times. I have other people who were there then, too, and who confirm my memories by sharing their own.

So how would I feel if someone—based on some piece of insight they thought they had allegedly received from the Bible or some other source—told me that in reality Scott Hoezee (and everything else for that matter) had been created in motion starting at my 45th year of life in 2009? Yes, everything about me—every DNA test available, every bone scan or memory scan or any other way by which the medical establishment could determine a person’s chronological age—all of it could confirm my 47 years but . . . my actual life would be but 2 years. So what about all those memories that stream to me from 42 years ago when I started kindergarten or from 19 years ago when my first child was born? What about the pictures, the videos, the others who remember it all, too? Well, they look and sound true but strictly speaking are not. None of those things happened (not in the way the last two years’ worth of stuff happened anyway). Installing those memories (of things that never truly took place) were necessary to make Scott’s appearance of age appear authentic but all of them (all 45 years’ worth of stuff) popped into existence at the same moment Scott did a scant two years ago. The events of the last two years are as real as they appear to me. The stuff from the previous 45 years . . . not so much.

If someone told me that it was God who did this all, I would conclude that God is cruel. That sense of cruelty would only be reinforced in case it were also true that within the human sphere of things, there would be absolutely no way I could know about the falsity of all those memories because in the proper exercise of my mental faculties and in the proper use of medical technologies by which my age could be verified, there would be no earthly reason to doubt the veracity of those memories or of the full 47 years they represent.

I would feel deceived.

The history of the universe—when stars were born, when they died, and other events that come to us in the streams of light that beam toward our planet every day—may seem far less personal than the birth of my first child or my remembering when Mom took me to kindergarten. But if all that cosmic information and history are not true—and if there is no way within the normal exercise of our human abilities to measure things to know any better—then why would God build up a story of the universe’s past life in case none of it (save for the last 10,000 years) ever actually took place but was made only to look as though it took place?

I would not like God to do that to me and the story of my life as I apprehend it. But I don’t like this concept any better when it applies to life beyond myself, either. That just doesn’t sound right.

And it isn’t.

]]> Thu, 03 Feb 11 11:32:56 -0800 Rev. Scott Hoezee