>
> Is there evidence for this? I'd assumed that population was controlled by
other than disease. After all, they had
> never heard of the "missionary position".

Yes many species regulate their population by regulating the rate of births
, and this have to do,  without us understanding how,  with the coming
availability of the food supply but not only .
bonobos  give birth to young every 5 years
despite they play with sex all the time ( prolonged breast feeding play an
anticonception role , having many partners do that  also )
chickens raised on grain will produce more eggs than chickens raised on
their natural diet ( unvertebrates and greens ) due to hormonal stimulation
of the unatural diet .
jean-claude