[Vinnie]

The females were the first bipedal. Down on all fours put them in an 'exposed' position. They got tired of being continously mounted. ( The headache hadn't been invented yet).
The females decided to try two feet only as a defense against the males.

[U S Army EOD]

You must have seen "Quest for Fire". As a result of that movie, I at times wonder what certain young ladies would look like bent over at the waterhole.