Monday, October 15, 2007

Pluralistic Darwinism

Every year I ask the undergraduate students in my course EEMB 102-Macroevolution the same question. "What do you think of when I say 'Darwin'"?

Some answers are jokes, like "The Darwin Awards". One common answer, "Darwin's Finches", was unexpected to me. But given the ubiquity of these birds in textbooks, perhaps I should not be surprised. Of course the most common answer is "survival of the fittest".

The reason I ask every year is that I like to point out two things in the first lecture of the course. First, that Darwin was not the only one to think up natural selection. A.R. Wallace famously scooped Darwin, and they published their ideas in 1858 at the urging of Charles Lyell. Two others had actually published the idea of natural selection, long before Darwin and Wallace thought of the idea, but in obscure places. I like to cite this when arguing for science as deterministic - a process unto itself that does not depend much on the individuals who practice it.

The second reason I ask is to highlight that Darwinism is so much more than just natural selection - despite most people's tendency to equate the two. All of the above answers (Darwin Awards, Finches, and survival of the fittest) re-enforce the idea that people often equate Darwinism and natural selection. The Darwin Awards go to people who do stupid things, and thereby "improve the accidentally removing themselves from it". The implicit idea is that removing people with genes coding for stupidity will improve the human species. Much research on Darwin's Finches is about documenting natural selection in the wild. And "survival of the fittest" is the most common buzz phrase referring to natural selection.

Never in my (admittedly small number of) years teaching the course has anyone mentioned any of the other Darwinian Theories (see Mayr's classification), besides natural selection. Why should this be, when global common descent is the most profound idea in all of biology? Global common descent provides explanatory power in biology. It is what scares anti-evolutionists the most, as the realization has transformed the view of humankind's place in the natural world from a self-congratulatory perch atop a Scalae Naturae, to an arbitrary outpost alongside other apes as cousins to every conceivable organism, from slime mold to germ.

It makes me wonder. Why is it that global common descent so often gets such a distant second billing to natural selection? Why do people so often equate Darwinism with natural selection, despite the fact that others conceived of natural selection (unlike global common descent, where as far as I know Darwin was the first) and despite the profound implications of common descent?

One idea is that humans - sometimes even practicing evolutionary biologists - have a difficult time coming to grips with global common descent. Perhaps a branching view of time is difficult to internalize compared to linear time. Perhaps it's all just a vestige of the great chain of being concept.

Questions and realizations about common descent are precisely what I want to contemplate in future posts.


AtlantAlex said...

I would guess that the reason people suggest natural selection and not common descent has most to due with the way evolution has been taught to us in the past. In high school, in particular, natural selection was emphasized in great detail, whereas common descent was an idea mentioned in passing. In addition, I previously considered common descent an implicit consequence of natural selection.

Todd Oakley said...

I totally agree. Natural selection is always emphasized in great detail.

Global common descent is not implicit in natural selection. If there actually were multiple separate origins of life, natural selection could still work in each of them.

Interestingly, Darwin himself tended to conflate natural selection and common descent (and its driving mechanism, which is speciation). This led to the famous irony that the book entitled Origin of Species (etc), didn't really discuss the origin of species. It wasn't until Dobzhansky and Mayr in the 1930s and 1940s that evolutionists began to really disentangle speciation and natural selection.