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Are Biologists Rejecting Neo-Darwinian Evolution?

As Paul Nelson recently observed, Robert Bishop's critique of Darwin's Doubt over at BioLogos tries to deny that any evolutionary biologists are entering a post-Darwinian world where they are abandoning neo-Darwinism. Dr. Bishop writes:

Meyer successively reviews a variety of attempts, such as evo-devo [evolutionary developmental biology] to rectify this shortcoming in macroevolution. Each attempt surveyed is presented to the reader as being in competition with and a replacement for neo-Darwinian evolution (population genetics and natural selection)....[but] researchers working in evo-devo typically don't see themselves as replacing population genetics and natural selection.

Of course none of these skeptical biologists are saying natural selection doesn't occur. (We're not saying that either.) Rather, what these post-Darwinian biologists are saying is that certain forces -- natural selection or random mutation, for example -- might not be as important in driving and shaping evolution as once thought. Thus, many examples could be cited where evolutionary biologists are specifically critiquing the core tenets of neo-Darwinism. And in fact Meyer cites many such examples in Darwin's Doubt (just read chapters 15 and 16 and see for yourself).

What's interesting is how many biologists say they are seeking new mechanisms of macroevolution -- thus implicitly rejecting the neo-Darwinian paradigm. What's even more interesting is that many are citing the Cambrian explosion as a reason for these efforts. Consider how Oxford's Simon Conway Morris has described current thinking in biology:

The other day I was walking past an immense building from which emanated uproar. The noise was terrific. A door swung open and, looking in, I saw to my surprise that nearly everyone was dressed in white. But, strange to say there was not one pulpit but two. The crowd surged back and forth, spotless laboratory coats streaming in the rush. From one pulpit the proclamation rang out: "The Cambrian 'explosion' is real!!! Hundreds of phyla evolved, almost instantaneously. Listen, neo-darwinism is in terminal crisis, we must summon forth new mechanisms of macroevolution". From the other pulpit, however, I heard the following: "No, the Cambrian `explosion' is a mirage, a mere artefact! For aeons tiny animalcules slithered through the slime, avoiding fossilization, hoarding their Hox genes, swaying to the sonorous tick of molecular horology."

(Simon Conway Morris, "Nipping the Cambrian 'explosion' in the bud?" BioEssays, 22: 1053-1056 (2000) (emphasis added).)

In other words, according to Conway Morris, the two main schools of thought about the Cambrian explosion are either (1) to claim it is simply an illusion, and an artifact of an imperfect fossil record, or (2) to seek "new mechanisms of macroevolution," rejecting neo-Darwinian explanations because they are "in terminal crisis". According to his report, many biologists are willing to question the neo-Darwinian paradigm itself. They are turning to what Conway Morris elsewhere calls "post-Darwinian" models of evolution.

Whether these post-Darwinian models solve the mystery of the Cambrian explosion (and the origin of new body plans) is another question. As Meyer reviews in chapters 15 and 16 of Darwin's Doubt, they don't look very promising. But the fact of the matter is that biology is uncovering evidence unanticipated by Darwin and the subsequent neo-Darwinian paradigm. And this evidence provides the impetus for post-Darwinian models of evolution, leading many biologists to say things like, "neo-darwinism is in terminal crisis, we must summon forth new mechanisms of macroevolution."