"Anyone approaching the Resurrection accounts in the belief that he knows what rising from the dead means will inevitably misunderstand those accounts and will then dismiss them as meaningless" (p. 243).

In fact, if Jesus' Resurrection were "merely" coming back to life in any way that we might comprehend, then it would be of little significance.

"Now it must be acknowledged that if in Jesus' Resurrection we were dealing simply with the miracle of a resuscitated corpse, it would ultimately be of no concern to us" (p. 243).

So what then does Resurrection mean? For Benedict it represents a new dimension of reality breaking through into human experience. It is not a violation of the old; it is the manifestation of something new.

"Jesus had not returned to a normal human life in this world like Lazarus and the others whom Jesus raised from the dead. He has entered upon a different life, a new life -- he has entered the vast breadth of God himself..." (p. 244).

Because it is something entirely new, it cannot represent a violation of natural law as understood by science.

"Naturally there can be no contradiction of clear scientific data. The Resurrection accounts certainly speak of something outside our world of experience. They speak of something new, something unprecedented -- a new dimension of reality that is revealed. What already exists is not called into question. Rather we are told that there is a further dimension, beyond what was previously known. Does that contradict science? Can there really only ever be what there has always been? Can there not be something unexpected, something unimaginable, something new? If there really is a God, is he not able to create a new dimension of human existence, a new dimension of reality altogether?" (p. 246-7)

Thus, in this view, Resurrection (as with all true miracles) is not contrary to science, but an indicator that science does not (yet?) describe the full expanse of reality. Indeed, some may argue that science itself contains similar "indicators." The 11 (or so) dimensional universe required by some versions of string theory, the multiverse theory of the universe where ours is but one of an infinite array of universes with variable physical laws, quantum entanglements, "spooky" action at a distance, the mysterious emergence of consciousness from inorganic matter -- all push the limits of human reason and imagination, suggesting to some that reality may be far more complex than the human mind can grasp.

For a moment, let us entertain the possibility that Resurrection is as Benedict interprets it: not a violation of natural law but an indicator of something beyond our scientific understanding of the universe. This has interesting implications for understanding how believers and skeptics approach the issue. If Resurrection does not violate science, then science does not necessarily constitute an impediment to accepting the reality of Resurrection. If the difference between the skeptic and believer is not science, then is it just a matter of imagination? The believer imagines greater possibilities for the universe than the non-believer. While this is possible, it seems questionable. To my knowledge, no research has found differences in imaginative abilities between religious and non-religious people. Moreover, contrarian examples easily come to mind: Isaac Asimov was an atheist but hardly lacking in imagination when it came to science fiction. I tend to think that both believers and non-believers can imagine (with varying degrees of effort, I'm sure) the new possibilities implied by Resurrection.

Thus, if it is neither imagination nor science that prompts skepticism about Resurrection, then what is left? I suggest that it comes down to a question of authority: At what point does one allow imaginative possibilities to have authority over how one lives? To the believer, Resurrection has an authority that science fiction does not. Resurrection is not thought-provoking entertainment. It requires far more than just imagining greater possibilities for the universe. It requires a change of life, here and now. Unlike the microscopic hidden dimensions of string theory, the new dimension implied by Resurrection has "broken though" into everyday reality and demands a response -- even if that response is to actively ignore it.

Now, what convinces the believer that Resurrection merits such authority when other imaginative possibilities such as extraterrestrial life or time-travel do not? The answer here appears to be historical commitment. There's no record of people committing themselves to the point of martyrdom to other imaginative possibilities as they have to Resurrection. The earliest example of such commitment being found, of course, in the dramatic post-crucifixion turn-around of the Apostles. Such an astounding change of heart, followed by an unwavering commitment capable of altering human history demands a categorically unique explanation: Resurrection.

The believer's argument, however, remains unconvincing to the skeptic. However impressive they might be, a change of heart and steadfast commitment do not necessarily add up to a new dimension of reality. Extraordinary claims require extraordinary evidence. Fair enough. So a key question regarding the interpretation of Resurrection is this: Is the post-crucifixion history of Christianity extraordinary? Does it compel the dispassionate observer to concede that a categorically unique event could plausibly be its best explanation?

It ought to be upon questions such as those above that skeptics and believers respectfully engage one another, rather than the simplistic and often acrimonious sloganeering that has increasingly become the norm.

Understanding John Polkinghorne: Theology of Nature

John Polkinghorne’s interest in natural theology is important, but what really sets him apart from most others is that he combines it with an equally strong interest in theology of nature, which is not the same thing. Where natural theology involves, “metaquestions about the pattern and structure of the physical world,” theology of nature involves, “metaquestions about how its historical process is to be understood.” Rather than “looking to the physical world for hints of God’s existence,” we look “to God’s existence as an aid for understanding why things have developed in the physical world in the manner that they have.” (Belief in God in an Age of Science, p. 13)

On this front, Polkinghorne advances a strongly Christocentric theology of creation, stressing Jürgen Moltmann’s notion of The Crucified God . In the context of Polkinghorne’s theology of nature, the point is that the Creator is the crucified and resurrected second person of the Trinity. Since I devoted a column to this before, I won’t say more here, except to alert readers to the singular importance this particular idea has for him—especially when facing the problem of suffering. “The insight of the Crucified God lies at the very heart of my own Christian belief, indeed of the possibility of such belief in the face of the way the world is.” (Belief in God in an Age of Science, p. 44)

Situating John Polkinghorne: The Resurrection of Jesus

Many Christians today see science as posing dangerous threats to their faith, challenging their understanding of the Bible and undermining core tenets such as the bodily Resurrection of Jesus, the historical basis on which the Christian faith stands or falls. “Evolution” is often identified as the problem, but the real danger is unbridled naturalism. A commitment to naturalistic methods, known as “methodological naturalism,” (MN) has been an integral part of science and medicine since the ancient Greeks. Those methods have been highly successful at producing a coherent, often very convincing picture of nature and the history of nature.

Advocates of Intelligent Design and some other Christians reject MN, but many Christians who work in the sciences and related fields (such as engineering, medicine, or the history and philosophy science) support MN as a properly grounded and properly limited way of understanding reality. In their view, a robust Christian faith is consistent with a commitment to MN, provided that the limits of scientific inquiry are not simply equated with the limits of rationally grounded belief. Polkinghorne fits squarely in this category.

To understand more clearly where Polkinghorne lies on the larger landscape of science and religion, let’s consider his approach to the Resurrection. Many contemporary thinkers, including some theologians and clergy, believe that “science” has somehow made it impossible to believe in the Resurrection, the deity of Jesus, and even belief in the transcendent God of the Bible.

A prime example is John Shelby Spong, a retired Episcopalian bishop whose books have sold more than one million copies. Spong sees the bodily Resurrection as a figment of the disciples’ imaginations, a vestige of a theism that now we must throw away like a threadbare suit of clothes. For Spong, Christians today need to go "beyond theism" throwing out the baby of divine transcendence—the fundamental truth of monotheism—along with the bath water of the credulity and mythology of the pre-modern authors of the Bible and the ecumenical creeds. Spong’s message is that “Christianity must change or die,” and all in the name of “science.”

As Spong likes to say, his work is very controversial, and not just among rank-and-file Christians. Scholars have also railed against him. “I have been attacked in books from the religious right by such people as Alistair MacGrath [whose surname is actually spelled McGrath], N.T. Wright, and Luke Timothy Johnson,” he complains (Why Christianity Must Change or Die, p. xvi).

I understand (with much sadness) that we live in a highly polarized age. Nevertheless, it’s difficult for me to grant much credibility to an author who identifies McGrath, Wright, and Johnson as representatives of the “religious right.” Indeed, if anyone here is distorting the news it is Spong, not they. As the (late) great Catholic biblical scholar Raymond Brown once observed, “I do not think that a single NT [New Testament] author would recognize Spong’s Jesus as the figure being proclaimed or written about.” (Birth of the Messiah, note 321 on p. 704)

Matthias Grünewald, The Resurrection (a wing of the
Isenheim Altarpiece, ca. 1515), Unterlinden Museum,
Colmar, France

Polkinghorne certainly understands science far more than Spong does, and his conclusions about the implications of science for Christian beliefs are markedly different. With respect to the Resurrection, he is basically on the same page with his friend Wright, whose profound book, The Resurrection of the Son of God, he cites with appreciation. Belief in the Resurrection is well supported by the evidence, and the Resurrection, itself, is “the pivot on which the claim of a unique and transcendent significance for Jesus must turn.” Considering authors like Spong (although he does not explicitly name him), he adds, “it would be a serious apologetic mistake if Christian theology thought that operating in the context of science should somehow discourage it from laying proper emphasis on the essential centrality of Christ’s Resurrection, however counterintuitive that belief may seem in the light of mundane expectation.” (Theology in the Context of Science, pp. 135-6)

Amen.

Looking Ahead

This is the Easter season, and I’ll return in a couple of weeks to begin examining Polkinghorne’s approach to the Resurrection more fully, using excerpts from the chapter on “Motivated Belief” from his recent book, Theology in the Context of Science.

References

Raymond E. Brown, Birth of the Messiah: A Commentary on the Infancy Narratives in the Gospels of Matthew and Luke. (1992).

John Polkinghorne, Belief in God in an Age of Science (1998).

John Polkinghorne, Theology in the Context of Science (2009). My review for First Things online is here.

John Shelby Spong, Why Christianity Must Change or Die (1998).

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.

Tonight and tomorrow, Christians around the world stop to remember and celebrate the birth of Jesus in Bethlehem just over two thousand years ago. The familiar narrative of Joseph leading Mary to the stable to give birth to the Messiah, of the angels telling the shepherds in the fields of the great event that was happening nearby, and of the three men from the east who came to pay homage to the new King of Israel is re-told or acted out in countless churches, schools and homes. And from countless pulpits, the message goes out that those events are not just a quaint story and an excuse to give gifts, but the central mystery of our faith—that God himself became one of us in order to redeem us and the cosmos from our bondage to sin and death. That mystery—that the Creator God is also the Redeemer Christ—has been to focus of our worship since the first days of the church, and is the subject of the 7th-century Latin hymn Conditor alme siderum, presented here in a new setting from Alex Mejias and High Street Hymns.

While this recording includes only verses one and three from the original text (given in full below), it adds a refrain that catches the spirit of the whole hymn and emphasizes the longing we still feel even in our Christmas joy—the “already, but not yet” state in which we find ourselves today, living between that first Advent and the second Advent yet to be: “Come, O come to us!” For while we know that God has come to us in Jesus—that his death and resurrection have redeemed us and the universe—we are still waiting for that final consummation, depending on the Spirit to be working out our salvation even now. Until the time when, as the hymn says, “all hearts must bow,” the entire BioLogos community invites you to join us in the blessed work of declaring, celebrating, and following the Christ who is both Creator and Savior.

Creator of the Stars at Night

Alex Mejias is the founder and director of High Street Hymns, a non-profit music ministry that exists to spread the Gospel and worship the Triune God in spirit and truth through hymns, psalms and spiritual songs. Alex grew up in New Jersey and outside Washington, DC, receiving a BA in Religious Studies from the University of Virginia and a J.D. from the University of Virginia School of Law. For the past 15 years he has been leading worship for churches and ministries, writing and recording both new and old hymns, and touring the east coast as a singer-songwriter. Alex is also committed to the power of the creative arts to advance the Gospel and promote justice and healing in the name of Christ, serving, supporting, and collaborating with several other non-profit ministries.

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?

Keeping History Safe

In the cold morning air with the sun not yet over the ridge, the place to begin preparation for summiting Mount Darwin is to ponder the reasonableness of miracles. Many Totalizers would like to ban miracles from university consideration and inquiry. Trouble is: human history is awash with credible people reporting miracles.

Modern academic tradition tends to try and maintain order. For historians it behooves us professionally to avoid accounts of alleged spiritual events. We find comfort in a little logical gymnastics that keeps history safe for us to wander in, a deceptively formulaic avoidance method that helps us avoid what people are telling us about extraordinary events in the past.

David Hume popularly articulated this logical gymnastics in an essay titled “Of Miracles” that was eventually printed in Enquires Concerning Human Understanding (1748). “I flatter myself,” Hume triumphantly proclaimed, “that I have discovered an argument . . . which, if just, will, with the wise and learned, be an everlasting check to all kinds of superstitious delusion, and consequently, will be useful as long as the world endures.”

His everlasting check on superstition begins with a circular argument that because miracles can’t happen, a reasonable person should not even listen to reports of them. Hume taught that though the normal job of a historian was to listen to the testimony that comes down to us from the past, there is a point at which you can close your ears. Hume knew that historical testimony can get wild, so he came up with a way to domesticate the wildness, a way to make history a zoo rather than allow it to be a jungle. His “Of Miracles” has been tremendously influential in the discipline of human history over the last two hundred and fifty years, not because his ideas are strong, but because his ideas are useful. Get rid of “superstitious delusions,” and the discipline of history can be turned from a safari into a form of home economics. Hume’s domestication of history is seductively simple. Instead of following the Aristotelian tradition of linking the credibility of hard-to-believe testimony to the credibility of the testifier, Hume recommended disregarding the testifier and focusing only on the testimony. This effectively removed the persuasive power from hard-to-believe testimony. Miracles need the credibility of an eyewitness in order to have persuasive power. Hume cut the power source from the unwanted testimony.

Essentially, Hume adopted the modeling technique that Darwin later used and is best seen in Global Positioning System (GPS) units. Hume recommended gathering testimony from the past and every region to create a general model of what humans generally experience. Using this mass of information, one should generalize standards of common experience. Now if anyone reports a miracle, the alleged event can’t be true because it does not conform to the generalized standards of common experience. (Of course, Hume had already refused to allow that any reports of miracles could be used even to generalize common experience.) It’s tricky. Its logic is circular. But it works to weed out awkward, quirky information. It is as if a domineering GPS unit created a sphere to serve as an abstraction for the earth, then insisted that the earth can’t have wobbling poles and flattening in the upper latitudes because the sphere in the GPS shows it can’t be true. Given a useful and trustworthy GPS, don’t listen to a scientist who might tell you something different than what the GPS tells you.

The circularity of this argument has been noted ever since Hume first proposed it, but Hume was a good writer and said what a lot of people wanted to hear. Miracles are impossible so miracle reports can’t be true. Don’t even listen to reports of them.

Balancing Likelihoods

Also embedded in Hume’s essay is the awkward “rule of logic,” most often called “Balancing Likelihoods.” By combining math and logic in an odd way, Hume’s “Of Miracles “ offered another way for historians to avoid thinking about miracles. Balancing Likelihoods has many names but is probably best stated by David Hackett Fischer, in his Historians’ Fallacies: Toward a Logic of Historical Thought, as “the rule of probability:”

“[A]ll inferences from empirical evidence are probabilistic. It is not, therefore, sufficient to demonstrate merely that A was possibly the case. A historian must determine, as best he can, the probability of A in relation to the probability of alternatives. In the same fashion he cannot disprove A by demonstrating that not-A was possible, but only by demonstrating that not-A was more probable than A. This is the rule of probability.”

This seems to be practical but is impossible. Balancing Likelihoods, in the way described by Fischer, cannot be used by historians in any normal practice. It is a talisman to keep history mentally safe from the wildness that is reported to exist. Logicians, especially mathematicians, have long criticized intellectual constructions like this. The “probability” that Fischer writes about is seemingly mathematical, but the math is simply implied to give a sense of strength to human feelings.

Before Hume wrote “Of Miracles” probabilistic logic had been advancing rapidly and there was a great hope that mathematical analogies would strengthen human thinking—even Christian apologetics. “Pascal’s Wager,” the most famous mathematical apologetic from the seventeenth century, equated eternal salvation with mathematical infinity and then applied it to a gambling formula. Antoine Arnauld, in The Port-Royal Logic (1662), and John Locke, in his Essay Concerning Human Understanding (1690) and Discourse on Miracles (1706), carried probabilistic math and logic into the handling of reported miracles. A half-century later, however, Hume reacted against Arnauld and Locke’s teachings that mathematical analogies could help in the discussion of the credibility of miracles. Hume insisted that to handle a reported miracle, a historian had to create two separate ratios, pro and con, for believability. The ratios were then to be weighed against each other. This is Fischer’s “rule of probability” quoted above. In the language of Hume’s era, this was proclaimed as the “calculus of good sense.”

Lorraine Daston, in Classical Probability in the Enlightenment (1988), offers an excellent study of Hume and the many eighteenth-century mathematicians who wanted to help bring rigorous quantitative thinking to what today would be called the humanities. Daston writes that by the 1840s, mathematicians realized that “the ‘calculus of good sense’ had become antithetical to good sense,” and that today most of what these early probabilists were trying to do is considered “patently absurd.”

In 1901, one of America’s preeminent philosopher-mathematician-logicians, Charles Sanders Peirce, wrote three essays attacking the way historians had adopted Hume’s bad logic: “A Preliminary Chapter, Toward an Examination of Hume’s Argument Against Miracles, in its Logic and in its History,” “Hume’s Arguments Against Miracles, and the Idea of Natural Law,” and “On the Logic of Drawing History from Ancient Documents especially from Testimonies.” Peirce showed that historians are in error when they talk of judging testimony by balancing probabilities because “in a scientific sense, there are no ‘probabilities’ to be judged.”

Probability, Peirce wrote, “is the ratio of the frequency of occurrence of a specific event to a generic event.” A testimony “is neither a specific event, nor a generic event, but an individual event.” Peirce further pointed out that what people were justifying by claiming Balancing Likelihoods was really simply relating “what they prefer to do” to what they don’t prefer. “Likelihood is merely a reflection of our preconceived ideas.”

Historians like me who teach in universities about the reasonable credibility of Jesus’ resurrection need to be students of Peirce not Hume on the subject of assessing the credibility of reports that come down to us from ancient history. Dealing wisely with reports of events verging on the incredible is just part of the normal job of being grounded in the social study of our complex human past.

“Come to history as a doubter,” Richard Marius advises in a historical methods manual. “Skepticism is one of the historian’s finest qualities. Historians don’t trust their sources. . . . Nothing is quite so destructive to a historian’s reputation as to present conclusions that prove gullibility.”

But Marius is wrong. In practice, historians have to trust more than doubt. In practice, historians, especially ancient historians, can’t rely on doubting. Historians have to be close listeners, discerning listeners, wise listeners, who sometimes have to make harmonies and stretch for belief.

There are several different kinds of arguments that people bring along these lines; I want to talk about just one. So first… the Heidelberg catechism, one of the forms of unity of the church I go to (the Christian Reformed Church), says

Providence is the almighty and ever-present power of God, by which he upholds as with his hand heaven and Earth and all creatures and so rules them, that leaf and blade, rain and drought, fruitful and lean years, food and drink, health and sickness, prosperity and poverty. All things, in fact, come to us not by chance, but from his fatherly hand.

And part of the way it comes to us—not by chance, but from his fatherly hand—part of the way God has designed our world, is that there is a great deal of regularity and dependability in our world. Of course, if it were not for this regularity and dependability, we couldn’t do the things that we actually do. I mean, for example, if I just wanted to walk off the stage—if, for example, all the sudden those stairs over there suddenly turned into a ladder going up—well, that would make it really difficult.

If you are trying to build a house, for example, you have this hammer, but all the sudden the hammer turns in to a goose or a pigeon. Again, that would make things really difficult…or if the nail turned into a worm…or if you get in the car and turn the key and the car turns into a camel, things would be really hard, much harder than they are. This regularity and dependability in our world is an essential condition of our being able to live in the world in which we actually do.

If the world were irregular enough, we would not even be able to live in it, but there are also, according to classical Christianity here (the Heidelberg catechism, for example) there are also special divine actions; sometimes God does things specially. There are miracles in Scripture: the parting of the Red Sea, for example, Jesus walking on water, Jesus changing water into wine. There are miraculous healings: Jesus rising from the dead, Jesus raising Lazarus from the dead, and so on. And according to classical Christians, many of them, perhaps most of them, are special divine actions. God, for example, responds to prayers. He works in the hearts and minds of his children to effect sanctification. There is, what Calvin called, the internal testimony or witness of the Holy Spirit, and there is what Thomas Aquinas called the internal instigation of the Holy Spirit. So, these things are all special actions on the part of God. God constantly causes events in the world. Ok, so far fair enough—what is the problem?

Many theologians seem to think there is a science-religion problem here. I don’t think any of the theologians of Biola think this, (I don’t know, but I doubt it) but many theologians do. For example, Rudolf Bultmann says, “The historical method,” which of course he thinks that is the method we should use, “includes the presupposition that history is a unity in the sense of a closed continuum of effects in which individual events are connected by the succession of cause and effect. This continuum, furthermore, cannot be rent by the interference of supernatural, transcendent powers.”

That’s what he says. Alright, there is this continuum that cannot be rent by the interference of supernatural (that would be God) or transcendent powers. So, it is a little bit like the laws of the Medes and Persians. You probably remember Daniel. Daniel was a favorite of King Darius, and well, the other courtiers became jealous of Daniel (they didn’t like it that the king liked him so well). So, they came to the king and said, “Oh king, live forever, we think it would be a great idea if you passed an edict to the effect that you alone can be worshipped. Everybody has to worship you and nothing else.” Well the king thought that over for a minute, and that sounded pretty good to him so he said, “I guess that it is a pretty good idea.” So he made this edict; he made this declaration: “Only King Darius is to be worshipped—no one else, nothing else.”

These courtiers knew that Daniel worshipped God, and they thought probably Daniel would keep right on worshipping God despite this edict. So they were watching Daniel, and he was, in fact, worshipping God. So they came to the king. Now the penalty for worshipping something else was to be thrown into the lion’s den and they said, “Well, king live forever, looks like Daniel has been violating this edict. You have got to throw him in the lion’s den.”

Well, the king didn’t want to do this because he really liked Daniel. He thought this was a miserable way to proceed, and he didn’t want to do it, but then they said to him, “O king live forever, and remember a law of the Medes and Persians cannot be abrogated, even by the king himself.” So once it’s put in place, not even the king himself can change it or abrogate it or go against it.

That is sort of the suggestion that you get here from Bultmann. Bultmann thinks, “Maybe God created the world and set it up in a certain way, but once he did that, not even he can interfere in it”—he uses that word interference—“not even he can do anything in it. He just has to keep hands off.” It is like the law of the Medes and the Persians.

Another theologian who agrees is John Macquarrie, who says,

The way of understanding miracle (and that would be one kind of special divine action) that appeals to breaks in the natural order and to supernatural intervention belongs to the mythological outlook, and cannot commend itself in a post-mythological climate of thought. The traditional conception of miracle is irreconcilable with our modern understanding of both science and history. Science proceeds on the assumption that whatever events occur in the world, can be accounted for in terms of other events that also belong within the world, and if on some occasion, we are unable to give a complete account of some happening, the scientific conviction is that further research will bring to light further factors in the situation that will turn out to be just as imminent and this worldly as the factors already known.

Ok again, no room there for special action. And the third thinker here, Langdon Gilkey (still another theologian), says something similar, but I will pass. I will not read that one in the interest of saving a little bit of time, but these three theologians, plus many others want to assert that there is something wrong with the idea of God acting in the world, acting in the world in a way that goes beyond creation and sustaining, or creation and holding things in existence. So they think, “Ok, God created the world; God sustains it in existence”…that is ok with them, but anything beyond that, God performing any miracles, raising Jesus from the dead, or for that matter working in somebody’s heart and mind in a special way, that, they say, is a real problem. The question is, what is the problem?

Well, the next little bit here…according to the Christian and theistic idea, God is a person; he has knowledge, loves, and hates. He has aims and ends. He acts on the basis of his knowledge to achieve his ends. He is all-powerful, all-knowing, and wholly good. Thirdly (noted above by the Heidelberg catechism), God has created the world. Fourth is God conserves and sustains and maintains in being this world he created, but fifth, at least sometimes, God acts in a way going beyond creation and conservation in miracles, but also in his providential guiding of history, his working in the hearts of people, his internal instigation of the Holy Spirit, and so on, and it is with that fifth category that these people have a problem. It is God’s special action in the world—action beyond conservation and creation—and miracles would be an example.

So we might think of these theologians as endorsing what we could call hands off theology. God has got to keep his hands off. God could create the world. God conserves the world, sustains it in being, but he can’t do anything else—that is as far as he could go. It is hands off theology, and Bultmann, even in this context, even talks about interfering. I mean if God did something in the world that would be interfering, which, when you think about it, is a sort of strange thing to say—I mean if God created the world, he is the omnipotent, omniscient, holy, good creator of the world—when you accuse someone of interfering, you are saying they are doing something they should not be doing, right?

So Bultmann thinks if God did something in the world that would be interfering, and he should be ashamed of himself. Ok, now why is this a problem? Their suggestion is that somehow it is contrary to science. It is contrary to science the suggestion that God acts specially in the world. I didn’t read that bit, but Gilkey says, "The causal nexus in space and time which the enlightenment science and philosophy introduced into the western mind is also assumed by modern theologians and scholars. Since they participate in the modern world of science, both intellectually and existentially, they can scarcely do anything else.”

From a presentation sponsored by Biola University’s Center for Christian Thought, and delivered February 12, 2012 at EV Free Church, Fullerton, CA. Used by permission.

In my previous essay, I discussed “Darwin’s finches” and how surprisingly little Charles Darwin himself had to say about them. In fact, it was actually the British ornithologist David Lack (1910-1973) who conducted the critical research that immortalized the finches in biology textbooks and popular lore. In 1973, the eminent German zoologist Ernst Mayr wrote:

Already well known among professional ornithologists, his work on the Galapagos finches gave David Lack world fame… There is no modern textbook of zoology, evolution or ecology which does not include an account of his work.¹

Ernst W. Mayr

Decades have passed since Mayr wrote these words, and David Lack’s name has largely faded from public discourse. On the other hand, the Galapagos finches have become one of the most recognized symbols of evolution in the world today. Does it really matter whether Lack or Darwin gets credit for describing the evolution of these remarkable birds?

Insofar as evolutionary theory contrasted with religious belief, it makes a big difference. In a culture that is eager to equate evolution with atheism, it should come as no surprise that these birds are only known as “Darwin’s finches”. Darwin’s personal struggles and ultimate rejection of Christianity are well documented, and people are eager to link his loss of faith to his evolutionary theory. David Lack, on the other hand, began his scientific career as an agnostic, but shortly after publishing his famous book on the evolution of Galápagos finches, he converted to Christianity! ²

A Christian at the forefront of evolutionary biology

Lack’s Christian conversion did not mark the end of his scientific achievements, either. In fact, he continued as a prolific researcher until just weeks before he died. Among his many achievements, he was Director of the Edward Grey Institute of Field Ornithology (1945-1973), Fellow of the Royal Society, and President of both the International Ornithological Congress (1962-66) and the British Ecological Society (1964-65). His fellow scientists held him in great esteem:

He was described as one of the most outstanding among world ornithologists; he was certainly this, but he was also one of the world’s leading evolutionists. All the time one saw developing his use of birds as material for the study of wider, deeper, biological problems.³

David Lack at the International Ornithological Congress, 1962.

Clearly David Lack was an outstanding scientist, and his commitment to Christianity did not tarnish, hinder, or undermine his research on evolution. But we might also ask, what was Lack like as a Christian? Did he keep his faith hidden from view, afraid that it might compromise his reputation as a scientist? Ernst Mayr, who interacted with David Lack professionally and personally for nearly 40 years, had this to say:

I have known only few people with such deep moral convictions as David Lack. He applied very high standards to his own work and was not inclined to condone shoddiness, superficiality and lack of sincerity in others. This did not always go well with those who preferred to compromise in favour of temporary expediency. David had been raised in an environment in which great stress was layed on moral principles and this attitude was later reinforced by his Christian faith. This explains his extraordinary unselfishness and modesty, and his great devotion to his family, to his students, to his friends, and to all the things that he lived for. The equanimity, indeed serenity, with which he faced death after his terminal cancer had been diagnosed is further evidence of the strength which his faith gave him.⁴

Like Asa Gray⁵ before him, and Francis Collins⁶ after, David Lack was an sincere, devout Christian, as well as a leading scientist who employed evolutionary theory to make brilliant discoveries about the natural world. Though Lack did not see any conflict between his scientific and Christian beliefs, he was sympathetic to the concerns of his fellow Christians. Therefore, ten years after publishing his masterpiece on Darwin’s Finches, Lack wrote another book entitled Evolutionary Theory and Christian Belief: The Unresolved Conflict.

Originally published in 1957, this book deals with the very same science and faith questions that Christians struggle with today— topics like randomness and chance, death in nature, miracles, and evolutionary ethics. While it would be unreasonable to expect anyone to completely resolve these matters, Lack offered numerous insights both as a devout Christian and one of the world’s leading biologists.

Let’s take a brief look at how Lack addressed some of these questions.

Blind Chance or Divine Plan?

Evolutionary theory does not invoke supernatural forces in explaining the history of life on Earth; instead, it relies on naturally-occurring processes to account for the vast diversity of life. Additionally, it explains animal behavior largely in terms of survival and reproduction, without appealing to any higher purpose of life. Taken together, does this imply that God is absent, and that our lives are ultimately meaningless?

David Lack responded,

Behind the criticism that Darwinism means that evolution is either random or rigidly determined lies the fear that evolution proceeds blindly, and not in accordance with a divine plan. This is another problem that really lies outside the terms of reference of biology. It is true that biologists have inferred that, because evolution occurs by natural selection, there is no divine plan; but they are being as illogical as those theologians whom they rightly criticize for inferring that, because there is a divine plan, evolution cannot be the result of natural selection.⁷

When rendering judgment on the ultimate meaning of life, biologists are speaking from their person beliefs, not from scientific authority. Moreover, Lack pointed out that many science enthusiasts have employed the concept of “randomness” in ambiguous and misleading ways:

Mutations are random in relation to the needs of the animal, but natural selection is not. Selection, as the word implies, is the reverse of chance.⁸

In support of his view, Lack pointed out that convergent evolution has produced uncanny resemblances between distantly-related species across the world, notably among marsupials in Australia. Different evolutionary trajectories can lead to very similar results.⁹

Death in Nature

After addressing concerns about the seeming “randomness” of evolution, Lack turned to another great concern, the role of death in natural selection:

Various writers–some Christian and others agnostic–have been troubled about natural selection not only because it seems too random, but also because it is so unpleasant.¹⁰

Image courtesy John Marsh Photography via Flikr

Genetic mutations are generally harmful, and for evolution by natural selection to produce new forms of life, an awful lot of organisms must die. For many Christians, it is inconceivable that a loving and merciful God would allow death on such a vast scale.

But Lack also pointed out that rejecting evolutionary theory doesn’t actually get rid of the problem of death. Regardless of what we think about evolution, the brute fact of mass extinction remains. Fossils of innumerable animals, plants, and microorganisms clearly demonstrate that the vast majority of species that have ever lived are now dead. It may be quite troubling for us to observe that our planet is a giant graveyard of natural history, but rejecting evolution will not change this fact.

Some Christians conclude that death could not have been part of the divine plan; instead, it must be the work of the devil, or the result of human sin. But this interpretation contains an implicit assumption that death is always evil. Is this really true? David Lack offered two intriguing insights:

Blue-cheeked Bee-eater (Merops persicus) pair in
courtship, seen in Basai, Gurgaon, India.
Image courtesy Koshy Koshy.

1. For a population to maintain a stable size, all births must be balanced by a corresponding number of deaths. A world in which no animals die is a world in which no animals are born. That means no reproduction, no courtship, and by implication, no singing birds—much to the dismay of ornithologists and people in love!

2. Some people, taking cues from Isaiah 11:6-7, suppose that in a perfect world, animals only eat plants. But in fact, plants themselves depend on the bacterial decay of dead organisms. If animals didn't die, then essential nutrients would disappear from the ground, and plants could not continue to grow. Eventually, there would be nothing left for animals to eat, and all life would cease.¹¹

Miracles

Many Christians are uncomfortable with evolutionary theory because it denies a miraculous, supernatural origin of life. They fear that if those miracles are denied, it might lead people to reject the possibility of miracles altogether, including the central feature of the Christian faith—the resurrection of Jesus from the dead.

As a devout Christian, David Lack certainly affirmed the fundamental tenets of the gospel. But at the same time, he explained to his readers that invoking miracles to account for unusual features of the natural world is not particularly helpful when trying to deepen our understanding of God’s great multitude of creatures:

[The biologist's] research depends on repeated observations. It need not, as popularly supposed, consist solely, or even mainly of measurements and experiments, but unless events are repeated, they cannot be assessed by science. Hence truly unique events come outside the domain of science, though biologists are not usually convinced when told they must, therefore, leave such problems as miracles to others. For one of the chief ways in which research has advanced is through the discovery of apparent exceptions to the known rules, and if further study shows the exceptions to be replicable, new regularities are revealed from which modified rules can be propounded. This method has been so successful that the biologist tends to doubt whether there are any types of irregularity, or seeming irregularity, that will not yield to it.¹²

But just because a scientist cannot repeat a particular event doesn’t mean it didn’t happen. Both natural history and human history contain unique events that only happened once. As we peer into the past, the difficulty of discerning fact from fiction inspires us to further investigate the mysteries that surround us.

Conclusion

David Lack’s book Evolutionary Theory and Christian Belief was quite insightful, but his enduring achievements took place in evolutionary biology, a place where many Christians are afraid to tread. While it is significant that he himself found no contradiction between his faith and his science, perhaps the greatest testament to the compatibility between Christian faith and evolution is the life he led as a believer in both. As we saw in Ernst Mayr’s candid praise, Lack reflected the light of Christ through both his personal and his professional relationships.

Today, many voices in our culture still insist that evolution is incompatible with a sincere faith in Jesus, but a careful look at history demonstrates otherwise. In the future, perhaps more people of faith will have confidence to study biology knowing that one of the most iconic symbols of evolution—the Galapagos finches—owe their fame in large part to a devout Christian named David Lack.

Notes

1. Mayr (1973) “David L. Lack.” Ibis: 433.
2. Larson, E. J. Evolution's Workshop: God and Science on the Galapagos Islands. New York, Basic Books, 2001: 218. See also Lack, David. (1973) “My life as an amateur ornithologist.” Ibis: 431.
3. Alister C. Hardy (1973). "David L. Lack." Ibis: 436.
4. Mayr (1973) “David L. Lack.” Ibis: 433.
5. For more about Asa Gray, see the BioLogos FAQ “How have Christians responded to Darwin’s Origin of Species?”
6. See Francis Collins’ autobiography The Language of God: A Scientist Presents Evidence for his Belief (New York: Free Press, 2007) (book info)
7. Lack, David. Evolutionary Theory and Christian Belief: The Unresolved Conflict. Methuen & Co., 1957: 67.
8. Lack, p65.
9. For more on convergent evolution and the possibility that evolution could be compatible with some form of divine purpose, see the work of Simon Conway Morris, especially The Deep Structure of Biology: Is Convergence Sufficiently Ubiquitous to Give a Directional Signal? Templeton Press, 2008.
10. Lack, p72.
11. Lack, pp75-76.
12. Lack, p82.

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.

(Written by the BioLogos editorial team)

In a recent lecture in Washington, D.C., Intelligent Design advocate Stephen Meyer noted that scientists and theologians are generally uncomfortable with the idea of "supernatural intervention" in natural processes such as evolution. He then posed the question, “What's so bad about supernatural intervention?” Meyer’s comment touches on a point of particular tension among Christians engaged in understanding how our science and our theology interact: the nature of divine action.

Much of the confusion in this area, however, stems from the inexact meaning of intervention, which—like evolution or Darwinism—implies different things to different people. All Christians affirm that God works powerfully in the world, doing extraordinary acts of creation and salvation. In common conversation, then, intervention tends to mean simply “acts that are recognizably or obviously God’s,” whether as dramatic as the parting of the Red Sea or as subtle as an individual believer hearing a clear call to repentance or to mission from the Lord. Even in this most casual sense, intervention tends to mean special occasions of God’s providential care, rather than his ordinary sustaining work.

But to Christian scientists and philosophers trying to understand God’s action in creation—especially how he might go about his sustaining role—intervention has another connotation: namely, that recognizing something as “divine action” requires it to be in violation of the natural laws which God himself established. Put another way, many Christian thinkers associate the word intervention with the idea that to act in the world God “must” act from outside the world. That view is a central tenet of deism, not Christianity. One response to Meyer’s comment, then, is to ask whether intervention is the only (or even a helpful) way of thinking about God’s work in biological creation. Is there another way of talking about “divine action” that does not restrict God's work to only extraordinary events? Can we conceive of divine action in a way God is never absent, distant, or in any way removed from the creation he sustains at every moment?

Finding such an alternative vocabulary to talk about the different ways God acts in his creation is the purpose of this short series introducing the work of theologian and physicist Robert John Russell. Russell’s book Cosmology: From Alpha to Omega explores the history of Christian thinking about divine action and proposes one model for how we might understand it in light of Scripture, the traditions of the church, and contemporary scientific explorations of the material world.

To be clear, Russell argues that God does unmistakably act in the world. He singles out the bodily resurrection of Jesus not only as a prime example, but as a truly unique event distinct even from Christ’s other miraculous acts during his ministry on earth. That is, the resurrection was an in-breaking of God’s new reality into the present one, something “beyond miraculous.” This series, though, offers his perspective on the more basic issue of how God might be at work in what we have called the “ordinary processes” of his world.

We begin our three-part series below with Professor Russell’s description of how views of divine action have changed throughout history (excerpted from Chapter 4 of Cosmology: From Alpha to Omega).

Historical background to the problem of divine action

The notion of God’s acting in the world is central to the biblical witness. From the call of Abraham and the Exodus from Egypt to the birth, ministry, death and raising of Jesus and the founding of the church at Pentecost, God is represented as making new things happen. Through these “mighty acts,” God creates and saves. Rather than seeing divine acts as occasional events in what are otherwise entirely natural and historical processes, both the Hebrews and the early Christians conceived of God as the creator of the world and of divine action as the continuing basis of all that happens in nature and in history.

The view that God works in and through all the processes of the world continued throughout Patristic and Medieval times. For example, God was understood as the first or primary cause of all events—where all natural causes are instrumental or secondary causes through which God works. The conviction that God acts universally in all events, and that we act together with God in specific events, was maintained by the Reformers and the ensuing Protestant orthodoxy. John Calvin (1509-1564) argued that God is in absolute control over the world and at the same time maintained that people are responsible for evil deeds. Questions about human freedom and the reality of evil were seen more as problems requiring serious theological attention than as reasons for abandoning belief in God’s universal agency.

Moreover, faith in God the creator was articulated through two distinct but interwoven doctrines: creation and providence. The doctrine of creation asserts that the ultimate source and absolute ground of the universe is God. Without God, the universe would not exist, nor would it exist as “universe.” Creation theology, in turn, has often included three related but distinct claims: 1) the universe had a beginning; 2) the universe depends absolutely and at every moment on God for its sheer existence; and 3) the universe is the locus of God’s continuing activity as Creator. The first two have traditionally been grouped in terms of creatio ex nihilo(creation from nothing), and the third in terms of creatio continua (continuing creation).

The doctrine of providence presupposes a doctrine of creation, but adds significantly to it. While creation stresses that God is the cause of all existence, providence stresses that God is the cause of the meaning and purpose of all that is. God not only creates but guides and directs the universe towards the fulfilling of God’s purposes. These purposes are mostly hidden to us, though they may be partially seen after the fact in the course of natural and historical events. The way God achieves them is hidden, too. Only in the eschatological future will God’s action throughout the history of the universe be fully revealed and our faith in it confirmed. General providence refers to God’s universal action in guiding all events; special providence refers to God’s particular acts in specific moments, whether found in personal life or in history.

Divine intervention arises in the Enlightenment

The rise of modern science in the seventeenth century and Enlightenment philosophy in the eighteenth, however, led many to reject the traditional views of divine action. Although Isaac Newton (1643-1727) argued for the essential role of God in relation to the metaphysical underpinnings of his mechanical system, and in this way defended the sovereignty of God in relation to nature, Newtonian mechanics depicted a causally closed universe with little, if any, room for God’s special action in specific events—and then only by intervention: that is, by acting as from outside that closed system. A century later, Pierre Simon Laplace (1749-1827, pictured left) combined the determinism of Newton’s equations with epistemological reductionism (the properties and behavior of the whole are reducible to those of the parts) and metaphysical reductionism (the whole is simply composed of its parts), to portray all of nature as a causally closed, impersonal mechanism. This in turn led to the concept of interventionism: if God were really to act in specific events in nature, God would apparently have to break the remorseless lock-step of natural cause and effect by intervening in the sequence and violating the laws of nature in the process.

The eighteenth century also saw the rise and fall of deism, in which the scope of divine agency was limited to an initial act of creation. According to deism, the universe was like a clock which, once built and set in place, proceeded to run on its own. David Hume (1711-1776) challenged the deistic (and theistic) arguments for God as first cause and as designer. In response, Immanuel Kant (1724-1804, pictured right) constructed a new metaphysical system which emphasized the mind’s role in organizing sense-data through universal categories of intuition and forms of sensibility. According to Kant, the sphere of religion lies not in our knowing (the activity of pure reason) but in our sense of moral obligation (the activity of practical reason). It is our ethical system, not our knowledge of nature, that requires us to postulate God, freedom and the immortality of the soul. The consequence of Kant’s thought for the West was the philosophical separation of the domains of science and religion into “two worlds”—a move which was to have an immeasurable effect on Christian theology up to the present.

Theology splits into conservative and liberal interpretations of divine action

As a consequence of the philosophical division of science and religion, theology in the nineteenth century was faced with a fundamental challenge not only to its contents and structure, but even to its method. The variety of responses to this challenge tend to fall into two groups: “liberals” largely accepted and worked within the terms of the discussion that modernity dictated while “conservatives” upheld traditional formulations and tended to reject “modernity.” The earliest and most influential figure among liberals was Friedrich Schleiermacher (1768-1834), who responded to Kant by locating religion as neither a knowing nor a doing. Instead religion is grounded in personal piety—the feeling of absolute dependence.

Schleiermacher held that theological assertions emerge from the immediacy of the religious self-consciousness. He understood God’s relation to the world in terms of “universal divine immanence” [the idea that God is present to the entire cosmos at all times], and he blurred the distinction between creation and providence by collapsing the later into the former. In a famous move he defined miracle as “. . . simply the religious name for event. Every event, even the most natural and usual, becomes a miracle, as soon as the religious view of it can be the dominant.” Schleiermacher’s arguments became characteristic of liberal Protestant theology throughout the nineteenth century and continued into much of twentieth century theological work.

The second half of the nineteenth century saw the rise of Darwinian evolution, which combined random variation and natural selection to explain biological complexity. To some in the nineteenth and twentieth centuries, the fundamental role of chance in nature seemed to undercut any notion of divine action in the world; to others, such as the Anglo-Catholic liberal movement in Britain and America, Darwinian evolution could be accommodated and even integrated into theology without interventionism, since God works immanently in and through the very processes of nature. In contrast, religious conservatives tended either to reject evolution as a whole or give it a limited acceptance with the proviso that the objective acts of special providence constitute divine interventions in nature.

The rise of neo-orthodoxy in the twentieth century

Protestant theology in the first half of the twentieth century was largely shaped by Karl Barth. In his rejection of nineteenth-century liberal theology, Barth returned theology to its biblical roots and focused it on the God who is “wholly other.” Recognizing that a religion founded exclusively on subjective experience is vulnerable to the critiques of Feuerbach and Freud, Barth and his followers held fast to the objective action of God in creating and redeeming the world. “The Gospel is . . . not an event, nor an experience, nor an emotion—however delicate! ... It is a communication which presumes faith in the living God, and which creates that which it presumes.” The ‘God who acts’ became a hallmark of the ensuing “biblical theology” movement which arose in the 1940s and 1950s. To many this movement seemed to offer a tertium quid between liberal and conservative theologies.

But do Barthian neo-orthodoxy and the biblical theology movement actually produce a credible account of divine action? On the one hand neo-orthodoxy attempts to distance itself from liberal theology by retaining biblical language about God acting through wondrous events and by viewing revelation as including an objective act. Yet on the other hand, it, like liberalism, accepts the modern premise that nature is a closed causal system, as depicted by classical physics. The result is that neo-orthodoxy seems to assert a contradiction: God does act objectively in nature (as conservatives believe) and God does so without intervening, violating, suspending or obstructing the ordinary processes of nature understood as a closed causal system (as liberals believe).

A third way between liberal and conservative theologies

Any purported “third option” will require an intelligible concept of objectively special providence which does not entail divine intervention. Such a concept could serve as a genuine tertium quid to conservative and liberal notions of special providence, combining strengths borrowed from each. Specifically, we will seek to speak about special divine acts in which God acts objectively in an unusual and particularly meaningful way in, with, and through events which serve to mediate God’s action. We will seek to do so without entertaining—in fact by refusing—the additional claim that God must intervene in, or at least suspend, the laws of nature. Those laws are themselves the result of and description of God’s continuous creation, after all. I call this type of divine action Non-Interventionist Objective Divine Action (NIODA).

In part 2 of this series, Tom Burnett will explore in more depth what Russell takes to be wrong with the Enlightenment concept of “supernatural intervention.” Part 3 will explain and clarify Russell’s theory of NIODA.

From Chapter 4, “Does ‘The God Who Acts’ Really Act? New Approaches to Divine Action In Light Of Contemporary Science,” in Cosmology: From Alpha to Omega by Robert John Russell, copyright © 2008 Fortress Press. Reproduced by permission of Augsburg Fortress Publishers. All rights reserved. No further reproduction allowed without the written permission of the publisher.

This ongoing series grew out of a conversation that Kenneth Keathley, the Senior Vice President for Academic Administration at Southeastern Baptist Theological Seminary and I had last year. We agreed that he would solicit a set of essays from scholars at Southern Baptist Seminaries who would specifically identify their concerns about what they perceive to be the BioLogos view of creation. In response to this request, Dr. William Dembski of Southwestern Baptist Seminary submitted the essay “Is Darwinism Theologically Neutral?” Although I do not consider my view Darwinian, I am sure that my view and that of others associated with BioLogos is perceived that way by some, so this gives me an opportunity not only to respond to his analysis, but to clarify my position on creation and how I think it is distinct from what Dembski calls “Darwinism."

God’s Activity in Creation

I will begin by summarizing my view of the nature of God’s activity in creation. I think that God created all living organisms, including humans, through the evolutionary process. Acceptance of creation through evolution does not mean that I reject the notion of a miracle-working God. On the contrary, I believe in the miracles of Scripture, and I believe that we’ve experienced God’s supernatural activity in our own lives. I stand in awe of a personal God whose activity is not constrained by natural laws, but also includes supernatural acts.

But what are the natural laws? Are not the the laws of nature simply a description of God’s ongoing and non-ceasing activity in the universe? The Law of Gravity, for example, is not something that God set up in the beginning, thereafter recusing himself from further involvement and exiting from the scene. Instead, the Law of Gravity works as it does because of the ongoing activity of God’s Spirit in the universe. So consistent is that activity that it can be described mathematically through scientific analysis. If God ceased to be active, however, then not only would the matter of this universe no longer function in a way which enables a mathematical description of gravity, matter itself would cease to exist. Paul, referring to Christ, writes “All things are created by him and through him.” Continuing, he goes on to state that “He himself is before all things and in him all things hold together” (Colossians 1:17). So he created in the beginning and, indeed, “…without him not one thing came into being.” (John 1:3) But it doesn’t end there: his ongoing activity is necessary for the universe to function. As the writer to the Hebrews declares “He sustains all things by his powerful word.” (Hebrews 1:4) The laws of nature, then, are simply a description of the ongoing activity of God which—because it is so consistent, dependable, and pervasive—points to the trustworthiness of God. Put another way, the activity of God is not restricted to that which we call the supernatural; it is all God’s activity. It is just that some aspects of God’s activity are so consistently repeatable that we can develop laws which describe the regularity of the divine activity which “holds” and “sustains” the universe. This latter type of activity is no less magnificent just because God does it continuously. Indeed, the Psalmist marveled at God’s natural activity and worshipfully reflected upon it.

On the other hand, the God we know through Scripture and personal experience also works in ways that are not mathematically predictable. We call this aspect of God’s action supernatural, and we seem to think of this facet of God’s work—this law-defying activity—as being more God-like. Indeed calling it super-natural suggests we think of it as God’s “turbo-charged” activity. But are not miracles simply a reflection of God choosing to work in a unique, non-customary manner to accomplish God’s purposes in God’s time? (See here for more detail.) When God works in this way, Scripture generally presents such activity in the context and purpose of God’s desire to enter into or renew a relationship with an individual or with a community of people. For example, God’s miraculous involvement in the lives of the elderly couple, Abraham and Sarah, led to the birth of their son, Isaac, and marks the beginning of God’s very special relationship with their descendents. God’s interaction with Moses through the burning bush initiated a new phase of God’s relationship with the Hebrew people as they moved out of slavery and back into the Promised Land. And of course, the supreme examples of miraculous activity are the incarnation, the empty tomb, and the resurrected Body. We worship a personal God whose desire for an ongoing loving relationship with humankind is first laid out in the early chapters of Genesis, but does not end there. In all divine activity—supernatural and natural—God is just being who God is: Creator, Sustainer, and loving Father. There are not two sets of activities, even though we label them “super” and “ordinary.” All are “super,” because all describe the activity of our supernatural God. Some are regular, predictable and ongoing, while other activities of God are not, for reasons often based in the fact that God is lovingly responsive and relational.

The Genesis narrative gives us no details about the mechanism by which God brought the universe and life into existence. God gave the charge: “Let there be lights in the dome of the sky..., “ “Let the waters bring forth…,” “Let the land bring forth…,” “Let the birds multiply…,” and, in response, we are told, it happened. Scripture does not explain how it happened, although as we read God’s other book—the book of nature—we see that God’s work extended over a long period of time. In these details, the Bible does not say whether the “bringing forth” was fulfilled through God’s natural activity (that which is regular, ongoing, and can be described by science) or God’s supernatural activity (that which is not regular and predictable). Given the many examples of supernatural activity in Scripture, we human beings tend to expect that for something as special as creation of stars or new species, supernatural activity would have been required. But we cannot derive this from the scriptural account and, therefore, it is wise not to second-guess how God might have worked based on the Scriptures.

Indeed, the distinction is softened by Scripture itself, which often speaks of God’s natural activity in ways that sound supernatural. For example, the Psalmist writes of God opening his hand to feed the living creatures (Psalm 104:28). We know how God does this and so did the Psalmist—he did it through natural means—but it was still God’s process and God’s provisions. Job speaks of thunder as being the voice of God (Job 40:9). We know God’s natural activity produces thunder and we can describe the laws that are responsible for it, but the fact that we know how it works certainly doesn’t negate the point being made in the book of Job. When the Psalmist describes the heavens as being the work of his fingers (Psalm 8:3), this does not negate astronomy’s description of the regular and ongoing processes that give rise to stars in God’s universe. Those processes are natural, but they are every bit as much God’s activity as if he were to take huge balls of matter and miraculously fashion sparkling stars with his hands.

Still, given that there is extensive supernatural activity exhibited in God’s interaction with Israel and in the life of Jesus, it is entirely possible that he did work supernaturally in fulfilling the creation command, as well. Even though the miracles described in the Bible primarily serve some theological or pastoral purpose that stems from God’s earnest desire to make his presence known and to deepen his relationship with humankind, we should reserve judgment about whether only God’s natural activity was responsible. It is not clear though, that supernatural activity would often be God’s chosen mode of action millions of years before humans had arrived. Thus, we should not assume with certainty that God would choose to use supernatural flurries of activity if his ongoing regular activity—that described through natural laws—would accomplish the same end, albeit over a longer period of time. For all we know, God may prefer slowness, even though we seem to be inclined to think that faster is better. After all, in the history of Israel and the church, God gave no new prophecy for 400 years before the coming of Christ, and it took the early church five centuries to come to a clear—albeit mysterious—understanding of the Trinity. Even now, two thousand years after Christ, we wait for his return.

In the next part, Darrel responds to Dembski’s lists of non-negotiables and clarifies how he sees BioLogos as different from “Darwinism”.

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.

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.

Introduction: What’s all the fuss?

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

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

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

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

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

Intelligent design advocate Stephen Meyer and others have written:

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

And:

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

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

Geologic Time Scales: How big was the bang?

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

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

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

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

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

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

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

Notes

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