Athropology Doco

I saw a documentary the other day about Chimpanzee monkeys in the savannah and they were speculating how human prehistoric ancestors first stood erect - on two feet/legs. 
They showed the monkeys standing up to see over tall grass.

Now that may well be the case but by just looking over tall grass does not appear to be a reason for animals to walk on two feet.

I have hunted rabbits for years, and they too rear up on their hind legs to look over long grass. Mind you the legs are not fully extended.
I had a hunting dog that used to do the same thing! Dogs stand up to do tricks, but they are not destined to walk on two feet/legs.

There are other animals that from time to time stand erect.

The diversity of nature is a pleasure and a fascination.