The Evolution of Evolution: Gradualism, or Punctuated Equilibrium?

In some ways I’m glad I’m not an evolutionary biologist, even though the subject matter is undoubtedly fascinating and fundamental. Here in the US, especially, it’s practically impossible to have a level-headed discussion about the nature of evolutionary theory. Biologists are constantly defending themselves against absurd attacks from creationists and intelligent-design advocates. It can wear you down and breed defensiveness, which is not really conducive to carrying on a vigorous discussion about the state of that field.

But such discussions do exist, and are important. Here’s an interesting point/counter-point in Nature, in which respectable scientists argue over the current state of evolutionary theory: is it basically in good shape, simply requiring a natural amount of tweaking and updating over time, or is revolutionary re-thinking called for?

I’m a complete novice here, so my opinion should count for almost nothing. But from reading the two arguments, I tend to side with the gradualists on this one. As far as I can tell, the revolutionaries make their case by setting up a stripped-down straw-man version of evolution that nobody really believes (nor ever has, going back to Darwin), then proclaiming victory when they show that it’s inadequate, even though nobody disagrees with them. They want, in particular, to emphasize the roles of drift and development and environmental feedback — all of which seem worth emphasizing, but I’ve never heard anyone deny them. (Maybe I’m reading the wrong people.) And they very readily stoop to ad hominem psychoanalysis of their opponents, saying things like this:

Too often, vital discussions descend into acrimony, with accusations of muddle or misrepresentation. Perhaps haunted by the spectre of intelligent design, evolutionary biologists wish to show a united front to those hostile to science. Some might fear that they will receive less funding and recognition if outsiders — such as physiologists or developmental biologists — flood into their field.

Some might fear that, I guess. But I’d rather hear a substantive argument than be told from the start that I shouldn’t listen to those other folks because they’re just afraid of losing their funding. And the substantive arguments do exist. There’s no question that the theory of evolution is something that is constantly upgraded and improved as we better understand the enormous complexity of biological processes.

The gradualists (in terms of theory change, not necessarily in terms of how natural selection operates), by contrast, seem to make good points (again, to my non-expert judgment). Here’s what they say in response to their opponents:

They contend that four phenomena are important evolutionary processes: phenotypic plasticity, niche construction, inclusive inheritance and developmental bias. We could not agree more. We study them ourselves.

But we do not think that these processes deserve such special attention as to merit a new name such as ‘extended evolutionary synthesis’…

The evolutionary phenomena championed by Laland and colleagues are already well integrated into evolutionary biology, where they have long provided useful insights. Indeed, all of these concepts date back to Darwin himself, as exemplified by his analysis of the feedback that occurred as earthworms became adapted to their life in soil…

We invite Laland and colleagues to join us in a more expansive extension, rather than imagining divisions that do not exist.

Those don’t really read like the words of hidebound reactionaries who are unwilling to countenance any kind of change. It seems like a mistake for the revolutionaries to place so much emphasis on how revolutionary they are being, rather than concentrating on the subtle work of figuring out the relative importance of all these different factors to evolution in the real world — the importance of which nobody seems to deny, but the quantification of which is obviously a challenging empirical problem.

Fortunately physicists are never like this! It can be tough to live in a world of pure reason and unadulterated rationality, but someone’s got to do it.