Did chickens decide they needed to lay eggs, or did eggs decide they needed to produce chickens.
1. People play with their hair because it is there. I don't think hair playing is some sort of species imperative. if it were, bald guys would probably all be psychotic.
2. Squirrels or whatever their ancestors were developed claws overtime because the ones that could climb the trees rather than waiting around for food to fall to the ground had a much higher survival rate. Plus being able to escape whatever was roaming the ground eating proto-squirrels.
3. Whales that didn't have a nice layer of blubber didn't survive because all of the good food was in the colder water. That's probably where all the hot whale babes were too.
and so on.
Aw, c'mon, Steve. The history of life is all about life finding an even more crazier way to survive. Isn't that phenomenon worth our attention...?
It is definitely worth our attention. It's even worthy of a lively debate about which is the cause and which is the effect!
My contention is that the effect is, in a lot of cases, the cause. Or, to put it less zenly [word?]: Life evolves and adapts because that is what life does as a matter of course; not just by accident.
A proto-squirrel will try to climb a tree and, eventually, the neccessary claws develop and we have a squirrel. It's a super-sized case of "Use it or lose it" that's maybe best described as "Need it and breed it".
Life is nothing if not creative!