A Response to David Gelernter’s Attack on Evolution (2 of 4)

A Response to David Gelernter’s Attack on Evolution (2 of 4) August 28, 2019

David Gelernter is a well-known professor, but he’s not a biologist. Nevertheless, he has written an attack on evolution that has been praised by a number of conservative and Christian sites.

Though Gelernter isn’t ready to say that Intelligent Design (ID) is the replacement, he is sympathetic. (ID has many problems that he ignores, some of which are addressed in part 1.)

Let’s move on to the two primary arguments he uses against evolution.

Cambrian explosion

Gelernter is impressed by the Cambrian explosion, the period during which the 30-some animal phyla evolved.

In the famous “Cambrian explosion” of around half a billion years ago, a striking variety of new organisms—including the first-ever animals—pop up suddenly in the fossil record over a mere 70-odd million years. This great outburst followed many hundreds of millions of years of slow growth and scanty fossils, mainly of single-celled organisms, dating back to the origins of life roughly three and half billion years ago.

Because this is his key argument against evolution, I’d like to respond in depth. Even though science continues to learn new things about this period, there is plenty to push back against the idea that the Cambrian explosion defeats evolution.

  • The duration of the explosion he gives (70 million years) is 13 percent of the time since it started. Is that too short for thirty phyla to develop? (Even if the duration is 20 million years, more typical of the duration given by biologists, the same question applies.) Surprise is only possible if we have a mismatch between how long it took and how long it should’ve taken—so how long should it have taken? And perhaps the explosion wasn’t as surprising as once thought. “The presence of Precambrian animals somewhat dampens the ‘bang’ of the explosion; not only was the appearance of animals gradual, but their evolutionary radiation (‘diversification’) may also not have been as rapid as once thought. Indeed, statistical analysis shows that the Cambrian explosion was no faster than any of the other radiations in animals’ history” (emphasis added). (An evolutionary radiation is a burst of diversity through speciation.)
  • If creativity is his point about the Cambrian explosion, note that only nine of these phyla have diversified widely. These nine have each produced thousands to a million species. The remaining ones, not so much. For example, two phyla have about a hundred species each. Two other phyla have about twenty.
  • The fossil record is an imperfect record, and the duration of the explosion is just a guess. Did other phyla develop beforehand but die out before they could leave a record? “The sparseness of the fossil record means that organisms usually exist long before they are found in the fossil record” (source).
  • Did these phyla develop earlier than thought but without hard body parts that fossilize well? “Since most animal species are soft-bodied, they decay before they can become fossilized. As a result, although 30-plus phyla of living animals are known, two-thirds have never been found as fossils” (source).
  • One hypothesis that explains the sudden beginning of the period of body plan creativity is that the ocean finally became transparent at that point, which meant that vision was now possible. This set off an arms race between predator and prey, with size, speed, armor, teeth, and more as competitive factors. Additional non-supernatural explanations are also possible.
  • In the big picture, the Cambrian Explosion isn’t that big a deal. Sure, it’s important to us, because it’s the period of animal diversification, and we’re animals. But animals are just one of six biological kingdoms. And above kingdoms are three domains. This diagram may kindle a little humility.

Source: Wikipedia

  • One example that shows there’s a lot more to evolution than the Cambrian explosion is the Great Ordovician Biodiversity Event, which produced many more animal genera than did the Cambrian explosion. (The Ordovician Period followed the Cambrian Period.) The Cambrian explosion was noteworthy, but so were other periods of biological flourishing.
  • Impressive though the Cambrian explosion may be, let’s not overestimate what it produced. The Cambrian period started 541 million years ago (Mya). Land plants didn’t appear until 470Mya. The first land tetrapods (vertebrates with four limbs) appeared 370Mya. Even the jawless fish of the Cambrian Period wouldn’t look much like what we think of as “fish.”

The ultimate evaluation of the Cambrian explosion comes from the people who actually understand the evidence, the biologists. And they still accept evolution. Non-biologist Gelernter’s puzzlement over the Cambrian explosion counts for nothing.

Synthesis of novel proteins

He next argues that evolution couldn’t make useful new proteins.

Your task is to invent a new gene by mutation. . . . You have two possible starting points for this attempt. You could mutate an existing gene, or mutate gibberish. You have a choice because DNA actually consists of valid genes separated by long sequences of nonsense. Most biologists think that the nonsense sequences are the main source of new genes. If you tinker with a valid gene, you will almost certainly make it worse—to the point where its protein misfires and endangers (or kills) its organism—long before you start making it better.

(“Long sequences of nonsense”? I thought ID proponents weren’t allowed to consider the idea of junk DNA.)

He likes the idea of nonsense sequences, by luck, switching on and creating useful new proteins because he has a ready response. The fraction of useful proteins out of all possible proteins is miniscule, so he can cross his arms here, confident that this route won’t yield the answer.

About a string of DNA nonsense being interpreted as a working gene to create a small (150-amino-acid-long) protein, he says:

Try to mutate your way from 150 links of gibberish to a working, useful protein and you are guaranteed to fail. Try it with ten mutations, a thousand, a million—you fail. The odds bury you. It can’t be done.

Guaranteed? You’re saying that evolution has no mechanism to create novel proteins, and you can prove it? Then write your paper destroying evolution, and collect your Nobel. That you’re wasting your time trying to convince ordinary readers rather than scientists betrays your agenda.

And if the repurposing-gibberish route won’t work, we could (dare I say it?) consider the other route, the mutation of a working gene. Suppose that a gene is copied with one base pair wrong. This is technically an error in DNA replication, but this new gene might make a better protein.

Alternatively, the gene might be duplicated (gene duplication is a well-understood error in DNA replication). With two of the genes, one can make the old protein, leaving the other to possibly mutate and give a shot to a new protein. And if the new protein is worse? Then natural selection won’t select for it.

Looks like he needs to reconsider his guarantee that new protein synthesis never works.

Next up: Gelernter weighs evolution against Intelligent Design in part 3.

I like to ask them how God did it.
If they can explain the how,
then in all likelihood the who will no longer be necessary.
This is the entire history of science in a nutshell.
— commenter ThaneOfDrones


Image from FunkMonk, CC license

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