It seems that the way humans mate is fairly unusual among primates. No, not the missionary position, but the fact that we don't couple randomly with each other, as bonobos do.
Anthropologists call this "a system that minimizes competition between sperm." In other words, human females usually only mate with one male at a time so his sperm don't have to compete with someone else's on the way to her eggs.
Anthropologists see evidence of this difference in the recent decoding of human and chimp genomes. Many anthropologists believe that the development of language was a necessary component to the way we organize ourselves sexually. Grunts and body displays just couldn't cut it.
Chris Knight has shown that language could never develop in the standard ape social structure where males contribute very little to survival, fight among themselves and take whatever females they want.
Come to think of it, that may explain the current devolution of language in some quarters. For more, go here.