It is still not very well understood how languages evolved in humans. (But they obviously did.)
Therefore, I found it interesting to read in a recent Science article:
Pity poor Viki the chimpanzee. During the 1950s, two psychologists raised Viki in their own home like a human child and tried to teach her to speak. Viki managed a rough approximation of only four words: mama, papa, cup, and (maybe) up. The following decade, researchers had much better luck with a chimp named Washoe when they tried to teach him American Sign Language. But few scientists think Washoe's impressive efforts represent true language (Science, 2 April, p. 38).
Such evidence that apes are poor at vocalizing, but fairly good at gesturing, has bolstered the so-called gestural theory for language origins. According to this model, the first human language consisted of signing, and articulate speech came later. In recent years, the gestural theory has gained the upper hand in many scientific journals and meetings. "Apes are much better at controlling their hands" than at vocalizing, says Fitch. "Their gestures are more intentional and more under control."It is hard to teach monkeys to speak vocally but not so hard to have them speak through hand gestures. If this was true about out common ancestors than perhaps we were able to communicate with gestures long before we could with words?
I also find this interesting as I keep hearing so many claims that infants can learn sign language easier than vocal language. Could this because speaking with gestures is somehow more instinctive? (Been in our genes longer?)