Biologists have discovered that wild chimpanzees communicate using similar gestures to humans (do they give researchers "the finger?") This will give linguists a clue as to how language evolved among humans.
Researcher Anna Roberts has identified 20 to 30 manual gestures used by chimps, a third of which are similar to those used by humans. These include beckoning to make someone approach and flailing their arms to make someone leave (so if you don’t want to be compared to a primate, watch your gestures). Roberts thinks they suggest that a common ancestor of both humans and chimps must have used similar gestures.