A rather old, but still interesting article which probably wouldn't be published today:
Barry and Bonnie Hewlett had been studying the Aka and Ngandu people of
central Africa for many years before they began to specifically study
the groups' sexuality...
What the Aka and Ngandu have in common, besides geography, is this: In
both cultures, men and women view sexual intercourse as a kind of "work
night." The purpose of this work is the production of children -- a
critical matter in an area with a very high infant mortality rate...
Is the strong cultural focus on sex as a reproductive tool
the reason masturbation and homosexual practices seem to be virtually
unknown among the
Aka and Ngandu? That isn't clear. But the Hewletts did find that
their informants -- whom they knew well from years of field work --
"were not aware of these
practices, did not have terms for them," and, in the case of the
Aka, had a hard time even understanding about what the researchers were
Read the whole article over here.