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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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?

In our previous essay, we learned that a tree summarizing species relationships can be built using DNA information, and how we can use DNA as a “molecular clock” to date ancient events. Both of these methods have made specific predictions about the origin of whales. If evolution is true: whales are related to the even-toed hoofed mammals and should share common ancestors with them; transitional fossil forms dating from about 45 to 50 million years ago should be found which can be shown to be related to both the even-toed hoofed mammals and modern whales; whales are most closely related to modern hippos, and should share a common ancestor with them.

What other types of information might we be able to use to construct a phylogenetic tree (i.e. a family tree) of species relationships? It turns out that characteristics of body structure also can be used – for example, the presence or absence of certain bones, or the specific shapes of those bones. An advantage of using bony features is that they can be recovered from fossils, whereas DNA (with only certain limited exceptions) must come from living organisms.

We can also derive functional information from an examination of bony features. The various protrusions, bumps and knobs found on bones usually have important implications. For example, smooth rounded areas at the ends of bones allow them to fit together and move easily. The shapes of such surfaces determine which bone motions are “allowed” or “disallowed”. Consider, for example, the motion of the forearm against the upper arm at the elbow. This is a “hinge” joint, whose normal motion is defined by the shapes of the upper arm bone and one of the forearm bones, where they meet each other. You might normally exercise the action of this hinge joint when you pick up a cup of coffee, bring it to your mouth, then set it back down again. Let’s try to imagine another motion. For this exercise we first need to get our arm into the proper starting position. Place your arm at your side, bent at the elbow at a ninety degree angle, with your palm up. Now, while keeping your palm up, let’s attempt to move your arm only at the elbow (no shoulder motion – that’s cheating!). Now swing your forearm out to the side and attempt to end up with your fingers pointed directly away from your side. Most of you will not be able to do this. If you can, it’s because your shoulder is rotating in spite of yourself. This motion at the elbow is normally not allowed. Hence a careful analysis of bone shapes can allow us to infer how the bones were used. This in turn can assist us in the task of phylogenetic (evolutionary) classification of organisms. That is, we will have more confidence in the grouping together of animals in our tree diagram if corresponding bones are used functionally in the same way.

Therefore we would expect that we could use various bony features to help us examine the predictions generated by our previous look at different types of DNA data. Are there any bony features that are particularly relevant to the even-toed hoofed mammals? Well, it turns out that there are. These are mainly running animals, and there are several features of their ankle bones, which taken together define the “allowed” motions which make them efficient runners. If one takes the various ankle bones of a large group of mammals, examines them carefully to note their shapes, scores that information into a table, then uses a computer program to build a phylogenetic tree, it turns out that all the even-toed hoofed mammals are placed together. So far, so good. But what about whales? Well, now we have an obvious problem. Modern whales are very specialized, - they have flippers which correspond to the forelimbs, and they have almost no hind limbs! I say “almost” because they do have small pelvic bones, which are not attached to the rest of their skeletons. But they certainly have no ankles. This is where the fossils should come in – if evolution is true, we should expect to be able to identify transitional fossils which are ancestral to whales which contain the characteristic ankle bony features of the even-toed hoofed mammals.

Now let’s look at bony features from the whale perspective. We have already mentioned the almost complete loss of hind limbs, and the presence of forelimbs modified into flippers. In addition, as air breathers, whales have a blowhole at the top of their skull. And as powerful swimmers, which use a large tail fluke in vertical motions, whales have enormous sets of muscles which attach to enlarged projections from their vertebral column. So if evolution is true, we should begin to see fossil forms which manifest changes in bony features which correspond to the gradual accumulation of these whale-like characteristics. However, we still need more, because these various bony features all would be expected to occur in largely or exclusively aquatic forms. We might expect this to correspond to the later stages of a transition from terrestrial even-toed hoofed mammals. But what about the earlier stages? It would be very helpful if we had some “defining” characteristic of whales, similar to the ankle structure of even-toed hoofed mammals.

It turns out that the structure of the bones of the skull and ear apparatus of whales are highly modified to allow efficient hearing underwater. The mechanical aspects of efficiently receiving sound through water are somewhat different than receiving sound travelling through air. If evolution is true, we should expect to be able to find key transitional fossil forms with a progressive series of modifications of the skull and ear bones, features which would not be found in any other mammals.

Now that we know what we should expect to see, if evolution is true, let’s look at what has actually been found in the fossil record. Over the last fifteen years or so, a series of fossils, many of them discovered in the Indian subcontinent, have fulfilled nearly all of our predictions.^1,2 Let’s look at the figure below (Figure 1), reproduced from a recent popular book on evolution.³ This shows a series of fossils, arranged in approximate chronological order, with a modern whale at the top. How old are these fossil forms? The entire fossil progression illustrated occurs from a little over 50 million years ago to about 40 million years ago. So a remarkable alteration in general body form occurred in a little over 10 million years. This time frame agrees well with the previous prediction from the DNA “clock” that we discussed in our previous essay. Second, the general change in body shape corresponds to what we predicted in our discussion of whale bony features above. That is, there is a gradual elongation and streamlining, there is a modification of the forelimb into flippers and progressive reduction of the hindlimb, the nostrils for breathing move toward the top of the skull to form a blowhole (not obvious from the diagram), and the vertebrae develop enlarged projections to support the attachment of swimming muscles.

Figure 1: Skeletons and Body Forms of Modern Whales and Fossil Ancestors
The reconstructed skeletons (black) from modern whales (top) and various ancestral skeletal forms (series below) are in chronological order (from Pakicetus up). Indohyus is an extinct whale “cousin”. Relative body size, to scale, is indicated by the gray shapes at the right of each animal.

There is probably little question that the last fossil species in the figure (Durodon) is well on the way to becoming a modern whale. However, it might be argued by a skeptic that the earlier species (like Rhodocetus, Ambulocetus, or Pakicetus), despite the “cetus” (whale) part of their names, are not so obviously “whale-like” that they deserve to be considered as fossil whale ancestors. However, remember the characteristic whale skull modifications for hearing? It has been shown very clearly that throughout this series of fossil species, the various bony changes necessary to support efficient hearing in water were being acquired in a stepwise fashion. Organisms earlier in the sequence had skeletal characteristics consistent with them being able to hear well in both air (using the “classic” mammalian hearing apparatus), and newly acquired changes to also allow better hearing in water. Later organisms in the sequence become increasingly specialized for hearing in water only.⁴

What of the earliest fossil shown in this diagram –Pakicetus? Careful examination shows that it has the features we would predict for an early whale ancestor. It has the ankle bone characteristics of the even-toed hoofed mammals (in fact these features are also found in several of the later fossil forms as well, ensuring their continuity). This confirms one of the predictions made by the DNA evidence we discussed earlier. Furthermore, it has some of the modifications of the skull bones necessary for more efficient underwater hearing, which were previously documented only for modern whales and their later (more obvious) ancestors.⁴ These features are also shared with the “whale cousin” Indohyus.⁵ Preservation of more of the skeleton of this latter species has allowed detailed analysis indicating characteristics likely shared with whale ancestors. Indohyus was probably a wading animal, which spent much of its time in the water. It appears to have fed mostly on land, so it is suggested that resort to the water was made to escape predators.⁵

Finally, we need to look back at the last prediction from our previous DNA evidence, namely that modern whales are most closely related to hippos. If evolution is true, we should expect to find fossil forms linking these two modern groups. This has proven to be a tougher nut to crack, mainly because the ancestral whales first appear about 50 million years ago in what is now south Asia, and the hippo family first appears about 15 million years ago, in Africa. The most recent tree diagram, produced by using a combination of skeletal features and DNA data, still supports this family connection, as shown by the following figure (Figure 2).⁶

Figure 2: Phylogenetic Tree Showing the Relationship of Modern Whales to Living and Extinct Even-Toed Hoofed Mammals
This tree is based on both bony features and DNA data. The organisms presented in blue are semi-aquatic or aquatic forms. Organisms shown in green are terrestrial even-toed hoofed mammals (Artiodactyls). In black is shown a member of the odd-toed hoofed mammals. In red is an extinct fossil ancestor group. (This figure is adapted from Fig 1a in Reference 6).

The blue lines in the diagram show species in which the skeleton is specially thickened, and the bone structure more dense. This is an adaptation which allows wading animals (like modern hippos and the fossil Indohyus) to be good “bottom-walkers” (it prevents them from floating due to lighter body tissues), and allows fully marine organisms (like modern whales) to have “neutral buoyancy” (so they don’t always tend to pop up to the water surface, like a cork). There has also been progress in clarifying the relationships between fossil ancestors of hippos and those of modern whales. A recent study of hippo evolution, based only on skeletal characteristics, has conclusively shown that the hippo family are descended from an extinct group of fossil Artiodactyls, known to go back more than 40 million years, and whose fossils are from southern Asia. Furthermore, this study produced a phylogenetic tree predicting that this extinct hippo ancestor group also shared a common ancestor with the fossil whales.⁷ Thus the investigation of hippo origins is independently leading us back toward the origin of whales. However, in this study the statistical support for predicted common ancestor of the ancient hippo group and the ancient whale group is not as strong as scientists would like to consider this “case closed”. What is necessary is more fossils, of the appropriate age in order to complete the story of hippo evolution. We still need that to fill in the details of the predicted relationship of hippos to modern whales.

Thus the “Whales’ Tale” is not yet complete. It is a story of scientific discovery in progress. As we finish, let’s briefly summarize what we have found out. Different types of DNA evidence agree that modern whales are most closely related to the even-toed hoofed mammals, despite the obvious great changes in limb anatomy of the modern whales. This prediction has been amply confirmed by the fossil record. The DNA sequence evidence predicted a time frame during which critical early events in evolution of whale ancestors should occur. This prediction has also been amply confirmed. Finally, DNA evidence predicts that modern whales are most closely related to hippos. There is some fossil evidence supporting a predicted common ancestor, but more data is needed. A final caution to possible sceptics – this state of “unfinished business” is precisely how the scientific process works. There is no “crisis”. There is no indication that evolution is not true. There is simply the ongoing work of mapping out of various lines of evidence. A scientific conclusion is considered well supported if “all roads lead to Rome”. In the case of whale evolution it might be prudent to say that the evidence has not quite converged in Rome yet, but that we are now in the suburbs. That is precisely what makes science interesting and fun. Stay tuned!

The next blog in this series can be found here.

References:

1: Thewissen J.G.M., Williams E.M., Roe L.J. and Hussain S.T. 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature. 413: 277-281.

2: Gingerich P.D., ul Haq M., Zalmout I.S., Khan I.H., Malkani M.S. 2001. Origin of Whales from Early Artiodactyls: Hands and Feet of Eocene Protocetidae from Pakistan. Science. 293:2239-2242.

3: Coyne, J.A. 2009. Why Evolution is True. Viking Penguin, New York. Pg 50.

4: Numella S., Thewissen J.G.M., Bajpai S.,Hussain T., Kumar K. 2007. Sound Transmission in Archaic and Modern Whales: Anatomical Adaptations for Underwater Hearing. The Anatomical Record. 290:716-733.

5: Thewissen J.G.M., Cooper L.N., Clementz M.T., Bajpai S., Tiwari B.N. 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature. 450:1190-1194.

6: Geisler J.H. and Theodor J.M. 2009. Hippopotamus and whale phylogeny. Nature. 458:E1-E4.

7: Boisserie J.-R., Lihoreau F., Brunet M. 2005. The position of Hippopotamidae within Cetartiodactyla. Proceedings of the National Academy of Sciences U.S.A. 102(5):1537-1541.

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

Transcript

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

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

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

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

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

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

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

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

A few editorial reflective thoughts by Darrel Falk: The sermon continues, of course, and you can download it at the above link. What is "the most important thing" to which Pastor Shaw refers as the audio clip draws to a close? Regardless of whether you think it is historical or not, what is the message that God wants to communicate to us through this story? Consider reading Genesis 9 right now. What are the parallels in this "recreation"account to the original creation account? What does God want us to see in making those parallels? What about the rainbow? What does it symbolize for you? Can you sense God's love for all of creation (not just humankind) as this story draws to a close? Why does the story of Noah himself, however, not have a happier ending? Have we seen the theme of nakedness and the need to cover up nakedness in an earlier scriptural passage? Why do you think the story of Noah draws us back to this point (nakedness and shame), just like the story Adam and Eve does? What brought on shame for them? What brings on shame for us? Do you see that God is wanting us to think deeply about this story and its meaning? What is another example of the need to cover up? (Hint: think Moses.) What difference does the coming of Jesus make to all of this? (Hint: see II Corinthians 3:12-18.) Do you see the rainbow?]]> Sat, 12 Nov 11 04:00:15 -0800 Pete Shaw http://biologos.org/blog/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.

Last week we debuted the first clip from the documentary “From the Dust”, directed by filmmaker Ryan Pettey. It is our sincere hope that, above all else, the film can become a focal point for some of the big questions that inevitably arise at the intersection of science and faith.

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

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

"The Book of Genesis" Transcript

Dr. Alister McGrath: “The Christian church has always wrestled with the interpretation of Scripture, realizing both how important it is and also sometimes how difficult it is to get it right. Certainly, the opening chapters of Genesis have been a topic of much debate throughout Christian history.”

Dr. John Polkinghorne: “The Bible is very important to me, but it is very important to recognize that the Bible is not a book. The Bible is a library. It has all sorts of different kinds of writing in it—It has histories, it has stories, it has poetry, it has prose. When we read Genesis one, we have to figure out, what am I reading? Am I reading a divinely dictated textbook to save me the trouble of doing science, or am I reading something, in fact, more interesting and profound than that?”

Dr. John Walton: “We have to approach Genesis 1 for what it is. It is an ancient document. It is not a document that was written to us—we believe the Bible was written for us like it is for everyone of all times and places because it is God’s Word—but it was not written to us. It was not written in our language. It was not written with our culture in mind or our culture in view.”

Dr. Alister McGrath: “It is not about the authority of Scripture, it is about the interpretation of Scripture. What method of interpretation do I use in the case of each individual passage?”

Dr. Karen Strand Winslow: “Biblical scholars urge people to take a literal, plain reading of the text…but I think in the controversy between theology and science, literal is often used to mean scientific, as if it is scientific, and that is a whole different story.”

Dr. John Walton: “We are inclined by our culture to think of the creation narrative as an account of material origins because we think about the world in material terms. For us, that is kind of what is important about origins. People come to Scripture thinking that they need to integrate it with science and so, they want to either read science out of the Bible or they want to read science into the Bible. That is not the way to do it because inevitably you end up making the text say things that it never meant to the ancient audience.”

Dr. Chris Tilling: “We are importing meaning into the text; we are bringing our own presuppositions and assumptions into a text and reading it in light of that as if it were in the text. Now, there is a sense in which we all inevitably do that, but there is also a sense in which we need to be aware when the times that we do that are damaging to the reading of the text.”

Dr. Nancey Murphy: “When I was a kid and the film industry was still relatively new, it was possible to depict people from two centuries ago as modern Americans dressed up in togas. As the film industry has gotten more sophisticated, they have gotten better and better at creating human figures that actually look and behave and think as they probably would have in the past. So, we Bible readers ought to be equally sophisticated and recognize that someone who was writing three thousand years ago, which is very hard to imagine, that these people must have been very different from us, with very different concerns. They certainly had very different understandings about how material things worked.”

Dr. Peter Enns: “One of the benefits of understanding the historical circumstances of the Bible is that we are reminded of how incredibly old this literature is. Let’s understand it in view of what we could even remotely expect of the Biblical writers to say.”

Dr. Nancey Murphy: “We can understand what our own creation stories are saying better, if we know what the creation myths were that were known at the times that those stories were written—for instance, to realize that a lot of the Genesis stories were written as a counter measure against the other cultures’ creation stories. That throws an immense amount of light on what parts of the story we are supposed to be paying attention to.”

Dr. Chris Tilling: “The Gilgamesh epic, for example, has a flood narrative and so forth, and so it wants to reflect creatively and theologically in light of those creation myths; it is going to be something recognizable.”

Dr. Peter Enns: “Genesis one shares theological vocabulary with the other stories—it just sort of takes things and turns it on its head.”

Dr. Nancey Murphy: “If one creation myth talks about the earth being created as a result of the battle between gods, we know to look in our creation stories to say, ‘wait a minute! Is violence intrinsic to the very creation of the universe?’ We find very clearly written that no, it is not.”

Dr. Peter Enns: “It’s Israel’s declaration that Yahweh is worthy of worship. It is a potent and counter-intuitive theological statement in the ancient world where people say, ‘That is totally different from anything we have ever seen.’”

Dr. John Polkinghorne: “The stories of the ancient world were not so concerned with minute, literal accuracy as we are today. People wrote not to give you sort of a factual, journalistic account of what is going on, but to tell you the significance of what was happening.”

Dr. Ard Louis: “And so what we see is that there are these really interesting structures in the Genesis text, which suggest that it is not describing the creation process as this is the order in which it happened. Rather, it is taking that story and emphasizing theological points. It talks about days; there was morning, there was evening—but the sun and the moon are not created until the fourth day. So why, for example, did the writer of Genesis put the sun and the moon on the fourth day? It is a very strange thing to do, and it is not as if it is only moderns who realize ‘Oh dear! Something is wrong.’ People at any time of history would have realized that that was an unusual way of writing down a journalistic account. And, of course, the reason most likely is that people of that day worshipped the sun and the moon, and the Israelites were always being drawn away that way, and the people around them were doing that. And so, what the writer was saying is, ‘no, I am going to demote these things to the fourth day. They are not the first thing to be created; they are something to be created somewhat later.’”

Bishop N.T. Wright: “This is simply the sort of language that people use to refer to concrete events, but to invest those events with their theological significance.”

Dr. John Walton: “We are well aware that people have to translate the language for us. We forget that people have to translate the culture for us, and therefore, if we want to get the best benefit from the communication, we need to try to enter their world, hear it as the audience would have heard it, as the author would have meant it, and to read it in those terms.”

Bishop N.T. Wright: “There is a distinction which is there in Scripture between heaven and earth. But the thing about heaven and earth is that they are supposed to overlap, and have an interesting, interlocking, interplay with one another. They are never supposed to be far apart.”

Dr. John Walton: “In the ancient world, they didn’t have a line between supernatural and natural. God was in everything. You couldn’t talk about God intervening because you can’t intervene in something you are doing—and to them, God was doing it all. That kind of functional aspect was very important to them.”

Bishop N.T. Wright: “In Genesis, God makes heavens and earth, and it appears that humans are in the world, but God is around as well because the heavens and earth have not split apart.”

Dr. John Walton: “The temple and the cosmos were all blended into one. If we used a modern metaphor it would almost be like the temple was the oval office. It is kind of where all the business is done, where all the work is run. It is the hub of activity and control, and when Deity took up his rest in the temple, it wasn’t for leisure or relaxation…it was to settle down to the work now that everything is set up and ready to go.”

Bishop N. T. Wright: “Telling a story about somebody who constructs something in six days, it is a temple story. It is about God making a place for himself to dwell…and this is heaven and earth. What you do with that is, the last thing is you put an image of this God into the temple. Suddenly, instead of Genesis one being about ‘were there six days or were there five or were there seven or were there twenty-four hours…,’ it is actually about when the good Creator God made the world, he made heaven and earth as the space in which he himself was going to dwell and put in humans into that construct as a way of both reflecting his own love into the world and drawing out the praise and glory from the world, back to himself. That is the literal meaning of Genesis. To flatten that out into, ‘this is simply telling us that the world was made in six days’ is almost perversely to avoid the real thrust of the narrative.”

Michael Ramsden: “If this is an inspired book, if this really is, you know, something where God is revealed and can speak through it, it shouldn’t surprise us that we find multiple layers of depth.”

Bishop N.T. Wright: “Genesis is one of those books like a Shakespeare play or like a Beethoven symphony or something where you can describe what it sort of literally says. Here is a Beethoven symphony; here are the notes, ‘Duh, duh, duh, duh.’ Then, you think, ‘well, that doesn’t actually catch what is going on in this’, and you want to use bigger language about the opening of Beethoven’s first symphony. This is an amazing statement about the power of empire and the fate of man…and goodness knows what! You still have got to play the notes. This world was made to be God’s abode, God’s home, God’s dwelling place. He shared it with us, and now he wants to rescue it and redeem it. We have to read Genesis for all it is worth. To say, either history or myth is a way of saying, ‘I am not going to study this text for what it is worth. I am just going to flatten it out so that it conforms to the cultural questions that my culture today is telling me to ask…and I think that is a form of actually being unfaithful to the text itself.”

Dr. John Walton: “The account in Genesis one is not intended to be an account of material origins. If that is so, then the Bible has no narrative of material origins, and if that is so, we don’t have to defend the Bible’s narrative of material origins against a scientific narrative because the Bible does not offer one. We can let the text be what it is and take it for what it is. That is the most literal reading that you could have.”

Throughout history, all civilizations and peoples have operated under the assumption of a cosmography or picture of the universe. Cosmography is a technical term that means a theory that describes and maps the main features of the heavens and the earth. A Cosmography or “cosmic geography” can be a complex picture of the universe that includes elements like astronomy, geology, and geography; and those elements can include theological implications as well. We are most familiar with the historical change that science went through from a Ptolemaic cosmography of the earth at the center of the universe (geocentrism) to a Copernican cosmography of the sun at the center of a galaxy (heliocentrism).

Some mythologies maintained that the earth was a flat disc on the back of a giant turtle; animistic cultures believe that spirits inhabit natural objects and cause them to behave in certain ways; modern westerners believe in a space-time continuum where everything is relative to its frame of reference in relation to the speed of light. Ancients tended to believe that the gods caused the weather; moderns tend to believe that impersonal physical processes cause weather. All these different beliefs are elements of a cosmography or picture of what the universe is really like and how it operates. Even though “pre-scientific” cultures like the Hebrews did not have the same notions of science that we moderns have, they still observed the world around them and made interpretations as to the structure and operations of the universe. The Bible also contains a cosmography or picture of the universe that its stories inhabit.

I have said this before, and I will say it again: I am not a scientist, I am a professional storyteller, and so my interest in Biblical cosmography comes from my study of imagery, metaphor, and story. But a picture of the cosmos certainly has a bearing on scientific notions of the way the universe is and operates. Imagination and science are not completely unconnected. I am also a Christian who believes that the Bible is the Word of God. But does this mean that the Bible will have a cosmography that agrees with modern western science? I used to believe it did. I used to believe that if the Bible was scientifically errant in anyway, then it could not be the Word of God, since God would never communicate false information to us. That would make God a liar, or so I thought.

This led to the corollary that whatever modern science has proven would have to be in accord with the Bible’s own revelation. This is called “scientific concordism.” So, if we now know that the earth is a sphere and that the universe is expanding, then Scripture would not contradict that truth. What’s more, I might even be able to find a verse that would have that truth hidden it: Behold, I thought I found it: “It is he who sits above the circle of the earth…who stretches out the heavens like a curtain” (Isa. 40:22). In this scientific concordist paradigm, the Bible contains veiled scientific truths before their time in a gnostic hiddenness that is uncovered by initiates into such mysteries.

Unfortunately, this paradigm would lead to much cognitive dissonance for me as I tortured the text to fit whatever scientific theory I was trying to support at the time. First, I accepted Genesis as literally explaining material creation chronology and relegated evolutionary scientists to dishonest manipulators of facts.¹ Then I tried to find dinosaurs in the Bible by interpreting the Leviathan or Behemoth as references to ichthyosaurs and sauropods.² Then I tried to make six literal days and young chronology of Creation in Genesis square symbolically with the seriously old age of the earth.³ Then I tried to creatively reconcile the billions of years of the Big Bang with 24-hour earth-bound solar days though gravity-warped space-time.⁴

I also thought that the best interpretation of the Bible was the “plain reading” of the text. That is, any interpretation that would turn the meaning into unwarranted figurative, symbolic, allegorical or metaphorical language would be disingenuous hermeneutics. I didn’t mean obvious figurative and allegorical language like parables of talking brambles and trees (Jud. 9:7-15) or clearly poetic expressions of singing mountains and clapping trees (Isa. 55:12). I meant that when the Bible talked about the physical order and events in heaven and earth it would mean just what it said since the Creator of the cosmos would know best what was actually happening.

But something started to seriously challenge these assumptions. First, as I studied the ancient Hebrew culture and its surrounding Near Eastern background, I began to see how very different a “plain reading” of a text was to them than a “plain reading” was to me.⁵ The ancient Hebrew mind was steeped in different symbols, ideas, and language than I was. If I read a phrase like “sun, moon and stars,” my western cultural understanding, which is deeply affected by a post-Galileo, post-Enlightened, materialist science would tend to read such references in terms of the physical bodies of matter, gas, and gravity spread out over vast light years of space-time. When ancient Israelites used that phrase, they would have pictures in their minds of markers and signs (Gen. 1:14), and more personal objects like pagan gods (Deut. 4:19), heavenly beings (1 Kg. 22:19), symbolic influential leaders (Gen. 37:9), or the fall of governing powers (Isa. 13:10).⁶

An ancient Jew hearing the words leviathan and sea conjured up notions of a disordered world without Yahweh’s rule, and Yahweh’s covenant creation out of chaos.⁷ Whereas for me, hearing those words makes me think of a monster fish swimming in the ocean – or maybe Moby Dick, a symbol of man’s hubris – but primarily the physical material being of those objects. It is easier to see now that my plain reading of the text through my modern western worldview could completely miss the plain meaning that the Scripture would have to an ancient Israelite. My so-called act of “plain reading” was ironically an imposition of my own cultural bias onto the text removed by thousands of years, thousands of miles, and thousands of cultural motifs.⁸ We must seek the “plain reading” of the ancient authors and their audience, and in this way we can be “diligent to present yourself approved to God as a workman who does not need to be ashamed, accurately handling the word of truth” (2 Tim. 2:15).

Something else had always haunted me like a nagging pebble in the shoe of my mind, and that was the Galileo affair. We’ll look more at this in my next post.

Notes

1. I never believed they were all lying, but many were certainly blinded by their worldview bias. I still believe that some scientists do in fact lie, cheat, and manipulate facts and studies just as in every other discipline because they are human like everyone else and can be just as driven by political and personal agenda as everyone else. A good book that documents this is Betrayers Of The Truth: Fraud And Deceit In The Halls Of Science By Nicholas Wade William Broad (Ebury Press, 1983); Michael Fumento is a science journalist who reports on current scientific fraud and its widespread economic and political effects at www.fumento.com.
2. Scientific Creationism by Henry M. Morris (Master Books, 1974, 1985) is an example of this viewpoint.
3. Creation and Time: A Biblical and Scientific Perspective on the Creation-Date Controversy by Hugh Ross (NavPress, 1994) is an example of this viewpoint.
4. Genesis and the Big Bang: The Discovery Of Harmony Between Modern Science And The Bible by Gerald Schroeder (Bantam, 1990) is an example of this viewpoint.
5. The seminal book that opened the door for me to a better understanding of this ANE cultural context of the Bible was John H. Walton, Ancient Near Eastern Thought and the Old Testament: Introducing the Conceptual World of the Hebrew Bible (Grand Rapids, MI: Baker, 2006).
6. “The worship of the host of heaven [was] often set in parallelism to the worship of foreign gods (Deut 17:3; 2 Kgs 17:16; 21:3; 23:4–5; Jer 19:13; Zeph 1:4–5).” K. van der Toorn, Bob Becking and Pieter Willem van der Horst, Dictionary of Deities and Demons in the Bible DDD, 2nd extensively rev. ed., 429 (Leiden; Boston; Grand Rapids, Mich.: Brill; Eerdmans, 1999), 429.
7. Brian Godawa, “Biblical Creation and Storytelling: Cosmogony, Combat and Covenant,” The BioLogos Foundation.
8. Othmar Keel’s The Symbolism of the Biblical World (Eisenbrauns) is an encyclopedia of imagery and motifs that Israel shared with her ANE neighbors that are quite alien to our thinking.