How I know there is a common ancestor

Why do primates have the irresistible urge to throw things?

As part of a promotional night to debut the new "Reggie Bar", a candy bar named after Reggie Jackson, fans at Yankee Stadium received free samples. The marketing scheme backfired though as fans threw hundreds of them back onto the field forcing the game to be halted until the ground crew was able to clear them away.

The only reason humans no longer throw our own dung is that no one will conveniently hand it to us.