And furthermore

The National Geographic article goes on to suggest that bipedality arose from the need for males to carry food to the females, for whatever reason; an old theory that’s been battered around for a while.

Pardon me, but that’s impossible. It violates one of the laws of evolution, which is that morphological changes are only made for food. Cosmetics for sex, morphology for food. Got it? Amoebas, birds, people, bacteria, grizzly bears, beans, and sequoias, we’re all the same: food for shape; sex for color. I’m not going to change my shape just to get you food.

It also edges on another evolutionary law: evolution only goes forward; it only moves in a positive direction. I.e. evolution is always towards something, never away from anything. The savannah theory directly violates that rule. One changes evolutionary direction because a new food source is appearing, not because an old one is disappearing.

(I feel the necessity to repeat these rules here because I don’t recall seeing them elsewhere, basic as they may be.)

Another evolutionary law often mentioned here: No species can evolve quickly enough to avoid environmental collapse. This is a correlate of the above law. Another reason why the savannah theory couldn’t be.