trobriand society problem

there is one well-known mystery about trobriand custom, and that is how, if
the adolescents go off for a few years by themselves and have free sex,
there are no babies till these years are felt as past, and parenthood
brings re-integration into village society. one loony possibility occurred
to me, thinking of a similar society today, how it might pay off for all
members to give out a free image, but not practise it : flirting all the
time....as then again in old age, but though allowed in parents is not so
really compatible with optimal parenthood, the test of any society. (ours
is notoriously insane.)