The presence of mothers may help find and successfully mate with just the right girl at the right time, at least in northern muriqui monkeys.
In a study of wild primates, University of Wisconsin-Madison anthropologist Karen B. Strier described 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 behavioural 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, said 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 found only in the Brazilian Atlantic Forest.
“The new data show who’s pulling the strings in muriqui society. It’s the mothers,” stated Strier.
“We knew from long-term behavioural studies that mothers, who can live into their thirties, stay with their sons for a lifetime, but the unexpected part of the story is that there may be reproductive advantages as a result of this living arrangement,” he added.
The finding was reported this week in the Proceedings of the National Academy of Sciences.