Beverly Strassmann at the University of Michigan in Ann Arbor has spent years studying the Dogon people of Mali, west Africa. Women who practise the traditional Dogon religion, unlike those who are Muslim or Christian, spend five days a month around the time of menstruation in a highly visible "menstrual hut".
Strassmann tested paternity in 1700 Dogon father and son pairs and found that those who practised the traditional religion were four times less likely to be raising someone else's son than those who practised Christianity (Proceedings of the National Academy of Sciences, DOI: 10.073/pnas.1110442109).
The findings suggest that the huts make it easier for husbands to monitor wives close to fertile periods. No differences were observed between the Dogon and the Muslim group, perhaps because women are required to tell their husbands when they menstruate.
Strassmann suggests that these traditions may have developed as a way to boost reproductive success.
New Scientist. 2012. "Menstrual huts protect Dogon men from cuckoldry". New Scientist. Posted: June 10, 2012. Available online: http://www.newscientist.com/article/mg21428684.100-menstrual-huts-protect-dogon-men-from-cuckoldry.html