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

Eric Bohlman (
Fri, 2 Jun 1995 23:30:32 GMT

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.

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