Brain evolution: Keeping your Witts about you

Discovery Institute Fellow Jonathan Witt has a post over on his blog (“Darwinism and Demarcation: Ducking the Debate”, see also his comments on that post and his subsequent post, Comments on Ducking the Debate).

Witt is quite confident that modern biology is totally wrong, but it’s clear that he doesn’t even understand the basics.

“Micajah,” a commenter on Witt’s blog, cites this press release about the cover story of this week’s issue of Cell. The Cell article, “Accelerated Evolution of Nervous System Genes in the Origin of Homo sapiens, gives new insight into how the human brain evolved.

Unfortunately, the comments by Witt in reply to “Micajah” and other posters indicate almost total unfamiliarity with the relevant science. It is, I think, an example of “this is your brain on ID/creationism.”

The commenter “Micajah” says,

You may have noticed the publication of a study yesterday which points to the apparently special nature of the human brain’s evolution.

Here’s the HHMI web page:

And, here’s the first sentence of the second paragraph in that notice: “The accelerated evolution of these genes in the human lineage was apparently driven by strong selection.”

Is it just me, or is that a relatively dogmatic way of explaining what happened?

The driving force for this “special event” was natural selection, according to these scientists’ view.

What, then, was the driving force for the wealth of beneficial genetic mutations which provided the opportunity for selection to work its “magic”?

It’s been a long time since I took a close look at evolution via natural selection, but isn’t it odd to point to selection as a driving force for a rapid mutation rate? It’s not quite the same as arguing that acquired characteristics can be inherited by offspring, but it seems to be similar.

Unfortunately for this poster, natural selection is directly detectable at the molecular level by comparing the synonymous and non-synonymous substitution rate. This is exactly what the article’s authors found. (Note that the substitution rate is what changes, not the mutation rate, as the commenter mistakenly claimed.)

The Cell article, “Accelerated Evolution of Nervous System Genes in the Origin of Homo sapiens,” is really a majestic piece of research. The authors compared the sequences of a whole bunch of nervous-system-associated genes between humans, macaques, rats, and mice. With high statistical significance, they discovered that these genes have evolved more rapidly in primates than in rodents, and furthermore more rapidly in humans than in macaques. In addition, they found a significantly higher ratio of nonsynonymous-to-synonymous substitutions, a clear indication that natural selection spread these mutations to fixation in the populations. The mutations occurred across a broad suite of genes, with no evidence of gene duplication or other obvious changes in complexity at the genetic level. A plausible model is that the changes occurred piecemeal, each random mutation yielding a bit more brainpower, or a more efficient use of that brainpower, being retained by selection. None of this is particularly surprising to anyone aware of evolutionary theory and the fossil record of hominids, but it is nice to begin documenting the changes on the genetic level. The evolution of the human brain is certainly “special,” but the evidence indicates that normal evolutionary processes produced it.

Witt’s replies are revealing:

1. Evolution of the brain: Witt doesn’t correct any of the above mistakes by the commenter, but instead replies, “The evolution of the brain doesn’t fit well at all with Darwinian gradualism” and goes on to discuss punctuated equilibria, as if that were relevant in this case. But brain size increases gradually in the human fossil record:

Why can’t the ID folks just admit, straight up, that the fossil record of human evolution is just about exactly what we should expect if Darwin was right?

2. Punk Eek: Witt continues,

The Neo-Darwinian theory called punctuated equilibrium tries to explain these supposedly rapid evolutionary events and the dearth of transitional forms in the fossil record (We should see millions transitionals; we only see a handful).

Punctuated equilibria is just allopatric speciation (that is, speciation of geographical isolates, a common process in the Recent) applied to the fossil record. It properly applies only to a transition between closely-related species – on the level of a horse/zebra difference. Stephen Jay Gould argued that, if allopatric speciation was the dominant speciation process in evolutionary history, transitional fossils between two closely related species would be rare at this near-microevolutionary scale (that’s right folks, Punk Eek is basically microevolutionary theory applied to the fossil record). Over larger-scale transitions, Gould was quite clear that lots of transitional fossils exist (for example, for the origin of birds, mammals, amniotes, tetrapods, elephants, sirenians, whales, humans, horses, rhinos, etc.). Gould has been on record on this point for 20 years:

I count myself among the evolutionists who argue for a jerky, or episodic, rather than a smoothly gradual, pace of change. In 1972 my colleague Niles Eldredge and I developed the theory of punctuated equilibrium. We argued that two outstanding facts of the fossil record – geologically “sudden” origin of new species and failure to change thereafter (stasis) – reflect the predictions of evolutionary theory, not the imperfections of the fossil record. In most theories, small isolated populations are the source of new species, and the process of speciation takes thousands or tens of thousands of years. This amount of time, so long when measured against our lives, is a geological microsecond . . .

Since we proposed punctuated equilibria to explain trends, it is infuriating to be quoted again and again by creationists – whether through design or stupidity, I do not know – as admitting that the fossil record includes no transitional forms. Transitional forms are generally lacking at the species level, but they are abundant between larger groups.

  • Gould, Stephen Jay 1983. “Evolution as Fact and Theory” in Hens Teeth and Horse’s Toes: Further Reflections in Natural History. New York: W. W. Norton & Co., p. 258-260.

…but creationists are so committed to the “no transitional fossils” dogma they just refuse to recognize these basic points. They’ve fooled the whole intelligent design movement into following in their misbegotten footsteps on this one.

3. Cambrian explosion: In a later comment, Witt continues,

The first commenter asked for one fact that doesn’t fit with Darwnism. The list of facts that don’t fit with what it predicted are almost endless. Darwinism has become dogma, though, so there’s always someone to offer a patch/revision to the theory where data doesn’t fit.

To take one of the more striking examples, the Cambrian explosion doesn’t fit Darwinism. Various patches have been tried to salvage the appearance of radically new animal forms in the geological blink of an eye–punctuated equilibrium, the artifact hypothesis, the Vendian radiation, the Deep Divergence Hypothesis, the idea that animals before the Cambrian were soft-bodied and, therefore, weren’t preserved. All of them fail.

Just one of the many evidences for why: Cambrian and Precambrian finds in sites like one in China do preserve Precambrian soft-bodied forms quite nicely. None are even remotely like what we find in the Cambrian. None are suitable precursors or transitionals. Again, see the Stephen Meyer article. It was peer-reviewed by experts in these fields, from Ivy league and other respected institutiions. The editor, who works in The Smithsonian Institution, has two relevant Ph.D.s, one in evolutionary biology. The article has been ridiculed but not refuted.

Witt strangely doesn’t link to the criticism he’s talking about, and relies on the authority of a guy, Sternberg, who is an odd enough duck to hang out with Baraminologists (this is rather like an astronomer hanging out with astrologers). We’ve been over all of the problems with Meyer’s PBSW article before, but it is worth mentioning that in that article, Meyer actually doesn’t go through the various hypotheses about the Cambrian explosion, except for Punk Eek which is irrelevant. Instead, Meyer basically says, “I don’t care how much time it took or how gradual it was, evolution can’t produce new information, full stop.” So Witt doesn’t really even know what’s in the Meyer article he recommends.

I also doubt that Witt actually knows that Meyer’s article was “peer-reviewed by experts in these fields.” Meyer’s paper makes elemental mistakes that would have been caught by any competent reviewer working in their specialty. Everyone can draw their own conclusions, but I doubt that the “experts” Sternberg chose as reviewers were actually experts in the relevant fields, namely information theory, the origin of genes, or Cambrian paleontology. If they were, I suspect this would have been trumpetted from the hilltops already.

Witt’s argument that soft-bodied fossils are preserved in the Precambrian, therefore if transitionals existed we would have found them, is hopelessly simplistic:

Just one of the many evidences for why: Cambrian and Precambrian finds in sites like one in China do preserve Precambrian soft-bodied forms quite nicely. None are even remotely like what we find in the Cambrian. None are suitable precursors or transitionals.

Witt doesn’t mention that the depositional environment changed drastically between the Precambrian and Cambrian. In the classic Edicaran rocks in the late Precambrian, algal mats covered the sediment (there were no algae-grazers yet), providing special conditions that allowed coarse features of the soft-bodied Edicaran fauna to be preserved. These conditions specifically do not allow for the preservation of millimeter-scale worms. Witt refers to one very special Precambrian site in China where Precambrian phosphatized sponge embryos were preserved, and – like Meyer and several other ID advocates – uses this one location as his silver bullet against all possibility of Precambrian bilaterians. However, we know these bilaterian worms existed, because their tracks have been preserved in many places. Even worse, the “silver bullet” recently hit the ID movement in the foot, because small bilaterian fossils were discovered at the same location. Witt neglects to mention this even though this very paper was cited in the critique of Meyer.

Given the ambiguity of Meyer’s position on gradualness and timing of the origin of the bilaterian phyla in the PBSW paper, Witt ironically defends the traditional creationist “poof” model of the Cambrian explosion, arguing that it represents the instantenous origin of modern phyla. However, the phyla were not modern, and the process was not instantaneous. This is true even if we look at a timeline from James Valentine – who basically argues that we should trust the fossils and not the molecular dates, an essentially “conservative” view:

590-550 mya – First appearances of metazoans 565-542 mya – Ediacaran fossils 570 mya – First fossils of metazoan tracks/trails 545 mya – First minute shells 543 mya – Offical base of the Cambrian 543 mya – First penetrating burrows 543-530 mya – Small shelly fossils, gradually increasing in diversity (tiny shelled metazoans and disarticulated skeletons) 530 mya – Tommotian, beginning of “Cambrian explosion”, which continues for at least 13 million years, perhaps 23 million years 530 mya – First brachiopods/mollusk fossils 525 mya – Atdabanian 525 mya – First echinoderm fossils, arthropod body fossils ~518 mya – Chengjiang fossil beds ~505 mya – Burgess Shale

Derived from James W. Valentine (2002). “Prelude to the Cambrian explosion.” Annual Review of Earth and Planetary Sciences. 30: 285-306.

So, even on the conservative view we have about 52 million years to get from the worms making the tracks in the Precambrian at 570 mya to the diverse – but still relatively primitive in modern terms (many stem-group forms) – fauna present at Chenjiang at 518 mya. In the trace fossils we have evidence of gradually increasing diversity all of the way, but mostly in millimeter-scale worms. Since the basal state within most phyla, or of close sister group phyla, appears to be of the worm/slug grade of organization, it’s hard to see where the miraculous intervention is required.

Readers may recall that Jonathan Witt recently felt well-enough informed on evolution to tell the hundreds of thousands of readers of the Seattle-Times that evolution was wrong and intelligent design was the “best explanation.” But all he’s got is an old-fashioned creationist’s understanding of the science, and he repeats canards that even the more sophisticated ID proponents shy away from. It’s hard to see how ID will ever convince the scientific community that it deserves to be taken seriously if it can’t even dissuade its lieutenants to avoid long-discredited creationist arguments.