Tuesday, December 28, 2010

Kin selection, or natural selection?

I've written about the "gay gene" before, and its possible implications. However, this snippet of the blog Bering in Mind started the wheels turning again:

Modern technological methods helping gays to be parents aside, there are many ways that childless individuals can still be genetically successful, in some cases more so than simply being a biological parent, such as investing heavily in biological kin who share their genes. (In scientific parlance, this is known as kin selection or inclusive genetic fitness.)

I've heard of kin selection before. I wonder what other "many ways" he refers to (though not enough to bother looking them up.) Anyway, modern technology, while opening direct biological success, simultaneously closes kin selection as a means of genetic success.

The rise of the single-child family is the key trend. With a single child, two adults (perhaps six, if both parents were singletons themselves), are already focused on the success of a single individual. The law of diminishing returns should apply here. The ratio of adults to children is already so high--6:1 isn't much different from 7:1--that the impact should be marginal. In addition, if the number of children is stable at one, an increase in resources will not increase genetic success. One child is one child, no matter the resources.

If kin selection is no longer effective, natural selection will become the dominant force in determining genetic success.


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