Evolution Icon Evolution
Human Origins Icon Human Origins
Paleontology Icon Paleontology

Missed Opportunity: Passing over Scientific Problems with Human Evolution

Casey Luskin
human origins
Photo: Skull fragment, Homo erectus, by Commie cretan (Own work) [CC BY-SA 3.0], via Wikimedia Commons.

Editor’s note: In a multipart series, Casey Luskin is reviewing a new book by philosopher William Lane Craig. Look here for the full review so far.

In his book In Quest of the Historical Adam, William Lane Craig’s rhetorical strategy is essentially to accept whatever mainstream evolutionary paleoanthropology says, and see if Adam and Eve can still stand. As he put it in an interview with Christianity Today, his “hope [is] that, by showing there is no incompatibility between contemporary evolutionary science and the affirmation of a single human pair at the headwaters of the human race, we can prevent that obstacle to faith.” Even a review of the book in the journal Science observes that Craig “takes evolution as a given.” In locating Adam and Eve within the species Homo heidelbergensis, Craig’s goal is to present a position of “reasonable faith,” and his tactical approach could indeed be useful for those who want to claim that the Bible is not in contradiction with mainstream evolutionary science. That’s fine as far as it goes. But this strategy means that sometimes Craig assents to evolutionary assumptions and arguments that are highly dubious, and he misses opportunities to point out severe weaknesses in evolutionary models.

Miracle Mutations and the Evolution of Human Intelligence

Craig focuses on various “crucial genetic mutation[s]” which occurred “in the human lineage since our last common ancestor with chimpanzees.” These could “explain the extraordinary expansion of the brain unique to human beings.” His primary examples involve a single base pair substitution in the gene ARHGAP11B and three human-specific NOTCh2NL genes (pp. 277, 278). He acknowledges that “we do not know” if these mutations had “any direct effect on language ability.” Yet he later cites human-specific features of two other genes that may be necessary for speech. These genes are AUTS2 (which Craig admits has an “unknown” function), and FOXP2 (which Craig argues “seems to be necessary for human speech”) (p. 325). In 2018 the FOXP2 story was discredited because the genetic signal that was thought to exist in the gene turned out to be a false statistical artifact,1 making it surprising that Craig continues to cite it.

Thus, aside from FOXP2 (which has been discredited), it’s not entirely clear what import these genetic traits have for human language and cognition. But let’s assume for the sake of argument that all of these “mutations” are necessary — though surely not sufficient — to explain humanity’s advanced cognitive and linguistic abilities. Craig never makes it exactly clear whether he views these mutations as arising and spreading via standard evolutionary mechanisms, or as having been guided by God’s intervention in the natural world. At one point he suggests the mutations could be “divinely caused” (p. 307), but his general framing lacks such qualifications, suggesting they are ordinary “mutations” that arose via standard evolutionary mechanisms. Writing in First Things, Craig proposes that “God selected two [hominids] and furnished them with intellects by renovating their brains and endowing them with rational souls” — which sounds like “divinely caused” mutations. In his book he is open to divine causation in the creation of Adam and Eve, but does not seem strongly committed to it:

The radical transition effected in the founding pair that lifted them to the human level plausibly involved both biological and spiritual renovation, perhaps divinely caused. (p. 376, emphasis added)

In First Things Craig then proposes that Adam and Eve were not as cognitively advanced as modern humans, and postulates that humanity experienced standard evolutionary changes after Adam and Eve including some that would “emerge slowly through environmental niche construction and gene-cultural coevolution” to evolve the more advanced brains we have today.2 What this suggests is that not only does Craig seem to propose or allow that many (if not all) of humanity’s intellectual abilities evolved via natural mechanisms, but he effectively believes we evolved upward after Adam and Eve — a model which contrasts sharply with the traditional Christian view that humanity has fallen from Adam and Eve’s initial state.

In his book it’s never quite clear if Craig thinks that the specific mutations he discusses occurred via standard evolutionary mechanisms, God’s direct intervention, or some kind of hybrid of the two. To give one of multiple examples, he says, “The most plausible scenario is that in a common ancestor of humans, Neanderthals, and Denisovans, the ancestral PDE4DIP-NOTCH2NL pseudogene was repaired by an ectopic gene conversion from NOTCH2. This event may have been crucial to human evolution…” (p. 279) To give another example, when discussing ARHGAP11B, he writes that Neanderthals, Denisovans, and humans:

share in this crucial genetic mutation that helps to explain the extraordinary expansion of the brain unique to human beings. Indeed, since the mutation occurred in the species ancestral to Neanderthals, Denisovans, and Homo sapiens, these findings are consistent with the humanity of someone belonging to a large-brained ancestral species like Homo heidelbergensis, in which the mutation occurred. (p. 278)

Perhaps these mutations were “divinely caused.” Yet in this retelling, whatever “divine causation” might mean (in Craig’s view), it appears indistinguishable from standard evolutionary explanations. Let’s set aside Craig’s ambiguity about what he means and just ask: What is the raw data here and does it demand assent to an evolutionary view?

At most, the data he cites simply shows that humans, Neanderthals, and Denisovans share certain similar genes and genetic traits which are involved in our brain development and linguistic abilities — genes and genetic traits not found in living apes. This is not at all surprising since Neanderthals and Denisovans were highly similar to us, are thought to have had advanced cognitive abilities, and may even belong within our own species Homo sapiens. The evidence he recounts is not evidence of evolution. Rather, it simply identifies human-specific genetic features that probably help endow us with our advanced cognitive abilities. Merely identifying important genetic traits does not necessarily tell us that they arose by blind evolutionary mechanisms. After all, these traits could have been intelligently designed or even specially created by God in the creation of Adam and Eve.

But Craig’s arguments typically seem to treat these mutations no differently from blind evolutionary events, which suddenly produced humanlike intelligence in some early hominid. Those of us who have been around the debate over evolution for a while have heard these kinds of miracle mutation stories before, and we have multiple reasons to be skeptical.

Reasons for Skepticism

First, miracle mutation accounts of the origin of human cognition imply a teleology and design to evolution that contradict an unguided evolutionary story. If our cognitive abilities suddenly evolved by just one or two single mutational events, that implies that our profound human intelligence was sitting on a precipice, just waiting for certain specific mutations to occur before modern human minds could arise. But how did our minds get to that evolutionary precipice, where just one or two mutations could produce everything from Lao Tzu to Beethoven to Einstein? The idea implies a teleological, directed, and designed course to the origin of our cognition. Craig seems open to this option, but he never says it is his preference.

Second, miracle mutation accounts of the origin of human cognition lack credibility and often go belly-up upon closer scrutiny. In The Language of God, Francis Collins asserted that a few specific changes in FOXP2 somehow created our major linguistic abilities.3 An article in Time Magazine that same year similarly asserted that two mutations in FOXP2 could have caused “the emergence of all aspects of human speech, from a baby’s first words to a Robin Williams monologue.”4 More recently Yuval Noah Harari argued in his book Sapiens that humans experienced some kind of a “Tree of Knowledge mutation” that occurred due to “pure chance” and caused a “cognitive revolution.”5

Such arguments that one or a few random mutations magically created humanity’s advanced intellectual abilities strain credulity. The origin of human cognition and speech would have required many changes that represent a suite of complex interdependent traits. Two leading evolutionists writing in a prominent text on primate origins explain that human language could not evolve in an abrupt manner, genetically speaking, because many genetic changes would be necessary:

Bickerton’s proposal of a single-gene mutation is, I think, too simplistic. Too many factors are involved in language learning — production, perception, comprehension, syntax, usage, symbols, cognition — for language to be the result of a single mutation event.6

Humans are quite different because they possess language, which underlies every major intellectual achievement of humanity. This discontinuity theory is implausible because evolution cannot proceed by inspired jumps, only by accretion of beneficial variants of what went before.7

These authors are correct to reject such “single mutation event” hypotheses — and would be justified in doing the same for two or three mutation events because human cognition is vastly too complex to arise in such a fashion.

Third, Darwinian evolution claims that these traits must arise and spread via random mutation acted upon by natural selection (and other standard evolutionary mechanisms such as genetic drift) — blind processes that operate without any intelligent oversight. Such a blind trial-and-error mechanism is highly inefficient at producing new features that require multiple mutations in order to provide an advantage. This is especially true when it comes to an advanced biological feature such as human intelligence, which probably requires numerous complex genetic traits. This suggests a potential challenge to the neo-Darwinian evolution of human intelligence.

Too Many Mutations, Too Little Time 

To understand this challenge, let’s consider a seemingly simple example. In 2004 a study in Nature proposed that a single mutation that inactivated a protein could cause “marked size reductions in individual muscle fibres and entire masticatory muscles” leading to “loss of masticatory strength,”8 which could have loosened jaw muscles, allowing our brains to grow larger. A news story widely circulated, titled “Missing link found in gene mutation,” framed the finding this way: “an ancient genetic mutation for weaker jaws helped increase brain size, a twist that first separated the earliest humans from their apelike ancestors.”9 The story sounds plausible, but there’s more to it. Leading paleoanthropologist Bernard Wood noted that this mutation alone could never have provided a selectable advantage, and would have required additional changes:

The mutation would have reduced the Darwinian fitness of those individuals. … It only would’ve become fixed if it coincided with mutations that reduced tooth size, jaw size and increased brain size. What are the chances of that?

We thus have a situation where multiple coordinated mutations would be necessary to provide the advantage. Yet a 2008 population genetics study in Genetics found that to obtain only two specific mutations via Darwinian evolution, “for humans with a much smaller effective population size, this type of change would take > 100 million years.” The authors admitted this was “very unlikely to occur on a reasonable timescale.”10 In other words, when a trait requires multiple mutations before an advantage is gained, it would require more than 100 million years within a species such as ours.

Craig did not cite the above example in his book, but it is highly analogous to the examples he does raise. He cites at least three mutational events (some of which might themselves have required multiple point mutations) as necessary for the advent of human intelligence. Undoubtedly, numerous complex mutational events would be required to transition from the apelike australopithecine intellect of our supposed ancestors to modern human cognition. If the Genetics paper cited above is correct, then if among these events, just two point mutations were ever required to yield an advantage, they would be extremely unlikely to arise via blind evolution in a population of hominids on the timescale allowed by the fossil record (i.e., ~750,000 years since the appearance of Homo heidelbergensis, or ~2.5 million years since our genus Homo supposedly evolved from australopithecines). 

This represents a potent challenge to the neo-Darwinian evolution of human cognition that flows directly out of the mathematics of population genetics. Unfortunately, because Craig never directly disputes mainstream evolutionary theory, his readers miss out on an opportunity to hear about this powerful challenge to neo-Darwinism.

Another Missed Opportunity to Challenge Human Evolution: Fossils

Craig doesn’t spend much time discussing the origin of the genus Homo, although he does cite anthropologist Ian Tattersall, arguing for “the futility of trying to divide what is now a very extensive hominid record between australopiths and Homo” (p. 256). In his quest to fit Adam and Eve within mainstream evolutionary science, he misses another major opportunity to point out a serious deficiency in the evidence for human evolution: the lack of fossil evidence documenting a transition from the ape-like australopithecines to the human-like Homo. This “gap” in the fossil record is well attested in the literature. 

One Nature paper noted that early Homo erectus shows “such a radical departure from previous forms of Homo (such as H. habilis) in its height, reduced sexual dimorphism, long limbs and modern body proportions that it is hard at present to identify its immediate ancestry in east Africa”11 — or anywhere else for that matter. Another review similarly notes, “…it is this seemingly abrupt appearance of H. erectus that has led to suggestions of a possible origin outside Africa.”12 Likewise, a paper in the Journal of Molecular Biology and Evolution found that Homo and Australopithecus differ significantly in brain size, dental function, increased cranial buttressing, expanded body height, visual, and respiratory changes, stating:

We, like many others, interpret the anatomical evidence to show that early H. sapiens was significantly and dramatically different from… australopithecines in virtually every element of its skeleton and every remnant of its behavior.

Noting these many differences, the study called the origin of humans, “a real acceleration of evolutionary change from the more slowly changing pace of australopithecine evolution.” It stated that such a transformation would have required radical changes: “The anatomy of the earliest H. sapiens sample indicates significant modifications of the ancestral genome and is not simply an extension of evolutionary trends in an earlier australopithecine lineage throughout the Pliocene. In fact, its combination of features never appears earlier.” These rapid and unique changes are termed “a genetic revolution” where “no australopithecine species is obviously transitional.”13

For those unconstrained by an evolutionary paradigm, it’s not obvious that this transition took place at all. The stark lack of fossil evidence for this hypothesized transition is confirmed by three Harvard paleoanthropologists:

Of the various transitions that occurred during human evolution, the transition from Australopithecus to Homo was undoubtedly one of the most critical in its magnitude and consequences. As with many key evolutionary events, there is both good and bad news. First, the bad news is that many details of this transition are obscure because of the paucity of the fossil and archaeological records.

As for the “good news,” they admit: “[A]lthough we lack many details about exactly how, when, and where the transition occurred from Australopithecus to Homo, we have sufficient data from before and after the transition to make some inferences about the overall nature of key changes that did occur.”14 In other words, the fossil record shows ape-like australopithecines (“before”), and human-like Homo (“after”), but not fossils documenting a transition between them. In the absence of intermediates, we are left with inferences of a transition based strictly upon the assumption of evolution — that an undocumented transition must have occurred somehow, sometime, and someplace. Evolutionists assume this transition happened, even though we do not have fossils documenting it.

Similarly, the great evolutionary biologist Ernst Mayr recognized the abrupt appearance of our genus:

The earliest fossils of HomoHomo rudolfensis and Homo erectus, are separated from Australopithecus by a large, unbridged gap. How can we explain this seeming saltation? Not having any fossils that can serve as missing links, we have to fall back on the time-honored method of historical science, the construction of a historical narrative.15

Another has commentator proposed that the evidence implies a “big bang theory” of the appearance of Homo.16

This large, unbridged gap between the apelike australopithecines and the abruptly appearing humanlike members of genus Homo challenges evolutionary accounts of human origins. Unfortunately Craig mentions none of this problematic evidence in his book. While he convincingly shows that Adam and Eve could be located within an evolutionary scenario, his readers are deprived of opportunities to learn why an evolutionary scenario might not be the right answer, after all.

Notes

  1. Matthew Warren, “Diverse genome study upends understanding of how language evolved,” Nature (August 2, 2018), https://www.nature.com/articles/d41586-018-05859-7
  2. Writing in First Things, Craig proposes a model of human intellectual origins that seems to include a combination of God’s direct involvement and natural evolution: “We may imagine an initial population of hominins—animals that were like human beings in many respects but lacked the capacity for rational thought. Out of this population, God selected two and furnished them with intellects by renovating their brains and endowing them with rational souls. One can envision a regulatory genetic mutation, which effected a change in the functioning of the brain, resulting in significantly greater cognitive capacity. Such a transformation could equip the individuals with the neurological ­structure to support a rational soul. Thus the radical transition effected in the founding pair that lifted them to the human level plausibly involved both biological and spiritual renovation. Some behavioral outworkings of this transformation would be immediate, whereas others would emerge slowly through environmental niche construction and gene-cultural coevolution.” William Lane Craig, “The Historical Adam,” First Things (October, 2021), https://www.firstthings.com/article/2021/10/the-historical-adam 
  3. See Francis Collins, Language of God: A Scientist Presents Evidence for Belief (Free Press, 2006), pp. 139-141.
  4. Michael D. Lemonick and Andrea Dorfman, “What Makes us Different?,” Time (October 1, 2006), http://content.time.com/time/magazine/article/0,9171,1541283,00.html.
  5. Yuval Noah Harari, Sapiens: A Brief History of Humankind (Harper, 2015).
  6. Charles T. Snowdon, “From Primate Communication to Human Language,” p. 224, in Tree of Origin: What Primate Behavior Can Tell Us About Human Social Evolution (Frans B.M. de Waal ed., Harvard University Press, 2001).
  7. Richard W. Byrne, “Social and Technical Forms of Primate Intelligence,” pp. 148-149, in Tree of Origin: What Primate Behavior Can Tell Us About Human Social Evolution (Frans B.M. de Waal ed., Harvard University Press, 2001). 
  8. Hansell H. Stedman, Benjamin W. Kozyak, Anthony Nelson, Danielle M. Thesier, Leonard T. Su, David W. Low, Charles R. Bridges, Joseph B. Shrager, Nancy Minugh-Purvis & Marilyn A. Mitchell, “Myosin gene mutation correlates with anatomical changes in the human lineage,” Nature, 428: 415–418 (March 25, 2004).
  9. Joseph B. Verrengia, “Missing link found in gene mutation?,” NBC News (March 24, 2004), https://www.nbcnews.com/id/wbna4593822
  10. Rick Durrett and Deena Schmidt, “Waiting for Two Mutations: With Applications to Regulatory Sequence Evolution and the Limits of Darwinian Evolution,” Genetics, 180: 1501-1509 (November 2008).
  11. Robin Dennell and Wil Roebroeks, “An Asian perspective on early human dispersal from Africa,” Nature, 438: 1099-1104 (December 22/29, 2005).
  12. Alan Turner and Hannah O’Regan, “Zoogeography: Primate and Early Hominin Distribution and Migration Patterns,” inHandbook of Paleoanthropology: Principles, Methods, and Approaches, ed. Winfried Henke and Ian Tattersall, 2nd ed. (Heidelberg: Springer, 2015), 623-642. 
  13. John Hawks, Keith Hunley, Sang-Hee Lee, and Milford Wolpoff, “Population Bottlenecks and Pleistocene Human Evolution,” Molecular Biology and Evolution, 17: 2-22 (2000).
  14. Daniel E. Lieberman, David R. Pilbeam, and Richard W. Wrangham, “The Transition from Australopithecus to Homo,” in Transitions in Prehistory: Essays in Honor of Ofer Bar-Yosef, eds. John J. Shea and Daniel E. Lieberman (Cambridge: Oxbow Books, 2009), 1.
  15. Ernst Mayr, What Makes Biology Unique?: Considerations on the Autonomy of a Scientific Discipline (Cambridge: Cambridge University Press, 2004), 198.
  16. “New study suggests big bang theory of human evolution” University of Michigan News Service, January 10, 2000, accessed July 10, 2016, http://www.umich.edu/~newsinfo/Releases/2000/Jan00/r011000b.html.

This Post Has Been Updated