Darwin Still Rules, but Some Biologists Dream of a Paradigm Shift

 
That's the title of an article in today's New York times. It's written by Douglas H. Erwin, "a senior scientist at the National Museum of Natural History at the Smithsonian Institution and a research professor at the Santa Fe Institute." You can read the entire article here.

Erwin says some rather silly things about "paradigm shifts" but I'll leave that to people like John Wilkins who know what Thomas Kuhn really meant. Suffice to say, the term is very much abused these days.

Putting that aside, Erwin makes some good points about the controversies in modern evolutionary theory. He points out that most of the old "paradigm" about evolution by natural selection is being challenged in one way or another. For example,

In the past few years every element of this paradigm has been attacked. Concerns about the sources of evolutionary innovation and discoveries about how DNA evolves have led some to propose that mutations, not selection, drive much of evolution, or at least the main episodes of innovation, like the origin of major animal groups, including vertebrates.

This is correct. There's a resurgence of "mutationism" that puts more emphasis on the role of mutation in evolution. This re-emphasis is not popular among evolutionary biologists but it's gaining ground.

Comparative studies of development have illuminated how genes operate, and evolve, and this places less emphasis on the gradual accumulation of small genetic changes emphasized by the modern synthesis. Work in ecology has emphasized the role organisms play in building their own environments, and studies of the fossil record raise questions about the role of competition. The last major challenge to the modern synthesis came in the 1970s and 1980s as my paleontological colleagues, including the late Stephen Jay Gould, argued for a hierarchical view of evolution, with selection occurring at many levels, including between species.

Again, these new ideas are all in play in modern evolutionary theory. The first refers to "evo-devo" and there's no question that some evolutionary biologists are rethinking evolution in light of the discoveries in developmental biology. (I think they're wrong, but that's not the point here.)

The last item refers to punctuated equilibria and hierarchical theory. There's little doubt that Gould's ideas have shaken up the old "paradigms."

I was disappointed that Erwin omitted the biggest threat to the old view of evolution, namely random genetic drift. While we've known about drift for decades the full scale of it's role in evolution is only now beginning to be appreciated. Most people still don't realize that random genetic drift is by far the most common mechanism of evolution.

[Hat Tip: Greg Laden]