Monday, March 19, 2007

Levels of selection (group selection)   posted by Razib @ 3/19/2007 08:44:00 PM

The topic of "group selection" emerges many times on this blog. My own issue with this debate is that semantics are often rather tortured...and people have to be on the same page for any intellectual utility to be derived. With that in mind, I would like everyone who wishes to discuss groups selection to read Elisabeth's Lloyd's entry in the Stanford Encyclopedia of Philosophy, Units and Levels of Selection. It's long, but pretty definitive as far as surveys go. I think it will suffice as a semantic recalibrator. Also, David S. Wilson, the main promoter of higher level selection, has a new paper out, Human groups as adaptive units. If the topic interests you, I suggest you check it out. I've only skimmed the paper, but I'll give it a closer look soon....

Update: I read Wilson's paper...and it really doesn't push the ball beyound what you'd find in Unto Others. I am reminded of an anecdote that Martin Gardner related about Rodulf Carnap and the animosity that Karl Popper held toward him, "...the distance between him and Popper was not symmetrical. From Carnap to Popper it was small, but the other way around it appeared huge...." It seems Wilson wants it both ways, on the one hand, the mainstream is already where he is, they simply don't recognize it, on the other hand there is going to be a seismic Kuhnian paradigm shift in the near future. I will excise a portion of Wilson's paper which I think illustrates the problem with his sort of theorizing:
As an example, consider a single group consisting of two types of individual, A and B. Type A individuals behave in a way that increases the fitness of everyone in their group (including themselves) at no cost to themselves. The idea of providing a public good at no private cost might seem unrealistic but is useful for illustrative purposes. Type B individuals are free-riders that enjoy the benefits provided by A-types without providing any benefits of their own. By increasing the fitness of everyone, the frequency of A-types does not change within the group (except by drfit)....

Continuing this example, suppose that there are many groups, not just one, that vary in their frequency of A and B types. Even though the frequency of A does not change within any group (except by drift), groups with a higher frequency of A will contribute more to the total gene pool than groups with a lower frequency of A. In effect, we have added a process of natural selection at the group level: a population of groups, that vary in their genetic composition, with corresponding variation in their contribution to the gene pool (fitness). Group selection provides the fitness differences that were lacking within groups. In the case of a no-cost public good, any variation among groups is sufficient for the A-type to evolve to fixation in the total population, because positive among-group selection is unopposed by within-group

Yes, and money grows on trees! Group selection will not be validated by a priori analysis, it needs to be supported by empirical examination. A few examples already exist, and more will no doubt emerge, but evolution is a science of variation. The issue is not whether something occurs, but its importance in the order of things. As Wilson states in his paper, everyone agrees in principle that group selection can occur, so why the need for a toy model to illustrate that it can occur in the best of all worlds? I guess I feel that I want my 20 minutes back.

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