I. Evolution is driven by opportunity, not necessity;
1. Evolution cannot outrun ecological change
2. Evolution cannot fill an occupied eco-niche
II. Evolution cannot anticipate
Two current theories of human bipedal evolution make the logical error of evolution envisioning a future condition and hence heading that way. One is the common theory that proto-humans stood up to lessen their surface area available to the sun. The second is Daniel Lieberman’s (see the PBS show, Becoming Human) suggestion that people stood up because it was more efficient to walk that way than to walk like a chimp.
As to the common theory, aside from the problem that the sun is rarely directly overhead, if it really were the case of less solar exposure in an upright posture, the benefits of such a posture wouldn’t be realized in a chimp-like walker until many, many mutations had passed; which means that there would be no selective pressure to maintain any one of those mutations active, if each were isolated. Selective breeding only works if each mutation provides immediate benefit, not a future one.
The argument is the same for the efficiency of human walking. It’s a result of evolution, not a goal of evolution. Evolution has no goals, it simply bulges out where the walls are the weakest.
I’ll stick with habitual tool use morphing into obligate bipedalism. We know that tool use preceded the split between chimps and humans, because chimps use tools today (unless you think they might have learned from us). But chimps only use tools occasionally. I’m willing to wager that our tool habits led to the split between us and our cousins.
It is a reasonable question whether or not a tree falling alone in the forest has made any sound. Why, Good God, do I keep on writing this for my eyes only? So that one day in the far distant future someone will stumble upon this and say, “Good Lord, look here, this fellow had it all figured out way back when.”
It’s not rocket science, ladies and gentlemen; it’s really not. Why, oh why, am I falling here alone?