Theravive Home

If you’re wondering what new year’s resolutions to make, you might want to consider adding another spouse or two.

According to a recent study of 2000 participants over two decades living in Tanzania, multiple husbands can be advantageous to women and children when times are difficult. While this scenario might not exactly play well in most relationships today, it seems that in that remote village in East Africa where the study took place, having an extra spouse can be a buffer in economic and social crises and help children live longer.

The study, titled, Unpacking mating success and testing Bateman’s principles in a human population, was published in Proceedings of the Royal Society B. The study looked at the differences between men and women in the effects of having multiple marriage partners on their production of surviving children.

“As scientists we don't actually hope to find anything,” study author of the University of California at Davis Department of Anthropology, Monique Borgerhoff Mulder, told us, “but rather we are interested in whether the patterns that we predict from theory hold with real data.”

Mulder explained to us that biologists typically find that, in mammals, because females must gestate and lactate, males benefit more from multiple spouses than do females. This is called Bateman's third principle.

“Bateman's principle would seem to suggest that men should value marrying multiple times whereas women would benefit more from staying faithful to a single husband,” Mulder told us. “This has generated many sexual stereotypes, but to me (and many evolutionary anthropologists) it seems to be a big oversimplification.”

The study participants were of Pimbwe ethnicity, and hail from a small village near the Rukwa Valley. The area is next to floodplains and is now known as the Katavi National Park. Mainly hunter-gatherers, the Pimbwe make their living through gathering honey and brewing beer. But due to changing weather patterns, the Pimbwe’s main staple of cassava and maize can be unreliable. As far as relationships, the Pimbwe do get married but they also allow easily divorce and have more sexual partners than marriage partners throughout their lives.

Mulder used data collected over a 20 year period in an East African village to look at how the marriage histories of individual men and women was associated with their success in producing children.

“We found that both men and women had more children the more years they were married (not surprisingly),” Mulder told us.

“However, when we looked at the number of different individuals a person married over their lifetime the pattern diverged. While men with multiple spouses had a lower rate of producing children than men with fewer spouses, women with multiple spouses had a larger number of surviving children over their lifetime than women with fewer spouses.”

The results were surprising to Mulder. She found the pattern unusual and in fact, determined that the pattern had never been seen before. However, she says, it is not surprising in this particular context where rural African villagers face challenges in supporting themselves and their families. Women may benefit from multiple spouses by replacing poor or sick husbands with men in better condition. They may also benefit from having multiple sets of in-laws on whom to call for help in tough times.

“Humans are a highly variable species. Simple biological stereotypes about gender differences models don’t explain very much,” Mulder told us. “However, more complex biological models, that take into consideration the ecological and social conditions that people face, can shed light on the variability in our species.”

Mulder says more comparative studies are needed of how marriage systems relate to the ecology of food production across different societies.