While driving home today, I was listening to a story on NPR about the discovery of Ardi, who is now considered the oldest human ancestor. A scientist who was interviewed said that one of Ardipithicus ramidus' distinguishing characteristics, one that clearly set it apart from earlier, more ape-like creatures, was its lack of large, fearsome canines. Male apes and chimpanzees use their oversized canines to intimidate other males and impress females. Without these, the scientist said, Ardi's male contemporaries would have had to resort to other meaures to woo females, most likely (and I quote) "exchanging food for copulation."
"And that," I thought, "is where evolution stopped."