Monday, January 21, 2013
Dawkins v. Gould & Plato
While cleaning up my basement today, I found a book I didn’t remember that I had. It’s Dawkins v. Gould: Survival of the Fittest, by Kim Sterelny. I have been interested in the Dawkins-Gould debate for some time.
Dawkins (along with philosopher Daniel Dennett) are “ultra-Darwinians”. They think that the central question in biology is how organisms are so well adapted to their environments and they hold that the answer is always natural selection. Moreover, Dawkins thinks that the primary unit on which natural selection acts is the genes or, more correctly, gene lineages. Organisms are just military vehicles built to carry and maintain their genetic architects, largely by victories in battle with other lineages. Finally, the larger level of evolution‑the emergence of distinct species‑is just the aggregate of events at the level of organisms and genes.
Reading a portion of Sterelny’s book tonight, I think I finally have a grasp of Gould’s counter position. Gould thinks that the basic question is why there are really a rather small number of basic organism forms and why there is so much stability in organic form over time. The basic division of the animal kingdom is into phyla, of which there are about thirty. Gould thought that they all appeared at about the same time and observes that there has been little change in the arrangement since. While adaptation surely continues, the era of phyla innovation seems to be well over.
Gould interprets this as pointing to species selection as one of the primary force in evolutionary history. From time to time, usually or always as a result of some big change in the environment (think comet strike), a lot of the biological landscape is scraped clean and there are openings for new types of organism. There are only so many basic possibilities in biological design space and only some are suited to the new environment. These are the ones that appear. In this account, it is the species that is the target of selection and limits on species design that account for the basic organic models. Chance plays a very big role in this, as it is chance that steers the comet or whatever else roles the dice.
By contrast, natural selection plays a minor role. Individuals in a successful line will tend to be, well, successful. Once the successful models have been established, there will be relatively little change until the next apocalypse.
I discussed the difference between chance, unintentional biasing, and intentional biasing in a previous post with the regard to explaining the origin of life. While unintentional biasing looks dubious as a solution to the origin problem, it strikes me that Gould took it very seriously as an explanation of the basic disparity of life, i.e. explaining why organisms fall into a number of basic patterns.
Consider the beetle. There are hundreds of thousands, if not millions, of distinct species of beetle. All of them (by definition) follow the same pattern. A second set of wings evolved into a retractable coat of armor protecting the functional wings. In the organic form of the species from which all beetles descend, there was unintentional biasing towards the beetle form. The proto-beetle, apparently having two sets of wings and whatnot was unintentionally biased toward a new and very successful area in design space.
I confess that this strikes me as a quarrel that does not force me to take sides. I suspect that Gould was right to insist on the importance of general forms and stability in evolution. I have often thought that the chief thing that Darwin explained was not how species come to be but why so many of them remain so stable over time. I like the emphasis on species selection because it looks to me like a modern version of Plato and I have the hots for Plato.
At the same time, Gould’s successful species types are successful because the individual members are well adapted to their environments. Even if cumulative instances of selection are less important in the explanation of general species forms than the ultra-Darwinians suppose, every species is just a bunch of critters and each critter has to make a living and leave a legacy. The emphasis on natural selection and adaptation is still the fundamental explanation of how organisms are adapted to their environment and how a general species is kept in business.