[unspun]

Then you haven't understood at all. Survival of the fittest is an ex-post concept, not an ex-ante. (I would have called it survival of the adequate, but my suggestion came too late.) You should read some biology texts.

Mutations (and other genetic happenings) propose and selection disposes. There's no teleology, just survival. Sometimes (as in the Toba erruption), location is important. Sometimes disease resistance is important. Sometimes naturally curly hair is important.

I am using the word "purpose" here not necessarily to determine cause and effect. My use of the word "purpose" is to describe relationship between an animal or person and that being's environment (everything with which the being interacts with). If you prefer to substitute words such as "functional relationship," or "orientation" those would work, too.

[unspun]

BTW, I think "survival of the adequate" is apt, too. I've also thought that since our physical universe doesn't have a perpetual motion machine, "survival of the least unfit" may be the most appropriate.

[Doctor Stochastic]

"Purpose" doesn't seem to be realted to "orientation" at all. "Purpose" generally is realted to "aims" and "goals" which have nothing to do with evolutionary theory. Evolutionary theory has no teleology.