>What I don't
>understand is why bipedalism developed
>and why Lucy evolved a first rate hand
>when she still had a third rate brain.
Bipedalism is a mystery, but all the apes have excellent hands. Opposable
thumbs allow a nice secure grasp on a tree branch. So Lucy got her hands
from her ancestors. Likewise her second-rate brain (hey, it was the best of
its time - not too shabby, really) is more or less the same as her other ape
relatives.
Hominids didn't gain hands, they lost them, going from 4 to 2.