Re: Breast Size (Was: Re: Homosexuality and genetic determinism)

Bryant (
5 Jun 1995 14:44:35 -0600

Eric Bohlman ( wrote:
>: Bryant ( wrote:
>: : You don't evolve. Lineages and populations evolve. Because fitness
>: : advantages shape many traits (adaptations), it's fair to say that those
>: : traits evolved TO provide those fitness advantages. Our opposable thumbs
>: : evolved TO grasp (Gil, leave that one alone, eh?)...
: Nope, it's not fair to say that. It implies that the "purpose" of a
: trait existed in advance of the trait's appearance. If a trait makes
: something useful (like grasping) possible, then the trait is likely to
: stick around; that's what natural selection means. But until something
: resembling the opposable thumb appeared, grasping didn't exist, so it
: could not have been a cause of the trait.

Function does not imply any such thing. The trait is shaped by the
selective pressure(s) favoring certain aspects of it. Insomuch as
purpose implies intentional processes, I'll make sure to use "function"
in the future. But once one understands how selection works, a little
working short-hand language isn't so horrible a thing. We talk about
evolutionary "strategies" all the time, but none of us means this literally.

: Evolution is *not* a directed process by which species converge to some a
: priori Platonic ideal; it's the process by which species become able to
: survive their current environments. What's adaptive in one environment
: may be maladaptive in another environment (and environments are
: constantly changing).

All of this is true...

:Unless some a priori Platonic ideals for
: environments can be found, the concept of "purposive" evolution is
: meaningless.

But this is silly. We understand you're point, but adaptations can be,
amongst friends, discussed in terms of their purposes or evolved functions.