Monkey Moms Are Key To Sons’ Reproductive Success

If you are a male human, nothing puts a damper on romantic success like having your mother in tow. If you are a male northern muriqui monkey, however, mom’s presence may be your best bet to find and successfully mate with just the right girl at the right time.

In a study of wild primates, reported this week (Nov. 7, 2011) in the Proceedings of the National Academy of Sciences, University of Wisconsin-Madison anthropologist Karen B. Strier describes a monkey society where equality and tolerance rule and where sexually mature males, still living at home, seem to get helpful access to mates by the mere presence of their mothers and other maternal kin.

The new study, which combines Strier’s long-term behavioral studies of wild muriquis with new genetic assays obtained from their scat, is important because it can inform conservation practices for critically endangered primates. But the study’s big surprise, says Strier, was evidence that could extend the ‘grandmother hypothesis,’ the notion that human females evolved to live well past their reproductive years because of the rearing advantages conferred by post-menopausal women on their grandchildren.

The northern muriqui is a large, long-lived, socially complex and critically endangered New World primate. There are at most 1,000 animals left in patches of the Brazilian Atlantic Forest , the only place the species is found.

The monkey has been the subject of intensive behavioral study by Strier and her Brazilian colleagues for nearly three decades. Muriqui culture stands in stark contrast to many other primate societies: It is egalitarian, peaceful, and reproductive success, it seems, is spread evenly across the males of a group instead of determined by male social rank, as it is in most other species.

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