Comment by wizofaus

There are definitely cultures where, for instance, polygamy is seen as the desirable goal (for men) and monogamy is the poor man's fallback. And cultures where abstinence/celibacy etc. is revered. I would be surprised if there'd never been a culture where heterosexual marriage (implying a life-long commitment etc.) was the exception rather than the rule. The Na of Yunnan is supposedly one such example though I know very little about it.