What's more is that men with more than 1 wife have lower levels of testosterone than monogamously married men.
For the study, Peter B. Gray of University of Nevada, Las Vegas, Peter T. Ellison of Harvard University, and Benjamin C. Campbell of Boston University, investigated the links between male testosterone levels and marital status among modern-day pastoralists in northern Kenya, of whom less than 1.5 percent consider their wives a source of emotional support.
Researchers say that their subjects, the Ariaal males, serve as herd boys until they reach puberty, at which point they are initiated, become warriors, and accumulate livestock. They marry late and have children around the age of 30, and value social bonds with male peers more than spousal bonds or familial bonds, they add.
"These findings add to the cross-cultural scope of published data on the topic of human pair bonding, parenting and testosterone. While a number of North American studies have shown lower testosterone levels among monogamously married men compared with their single counterparts, no study outside North America had observed this," the authors say.
To test their theory, the researchers measured testosterone in morning and afternoon saliva samples of more than 200 Ariaal men over the age of twenty.
The analysis showed that monogamously married men had lower testosterone levels than unmarried men in both the morning and afternoon. However, contrary to expectations, married men with more than one wife (polygynously married men) had even lower levels of testosterone that the monogamously married men.
"These results lend further support to arguments that male testosterone levels reflect, in part, variation in male mating effort," the authors say.
"[However], contrary to earlier findings . . . polygynously married men did not show higher testosterone levels. In fact, follow-up analyses among Ariaal men aged 40 and older revealed lower testosterone levels among polygynously married men compared with monogamously married men," they add.
The researchers suggest that this may be due to the fact that it is older men - who typically have lower testosterone levels - who have the social status and wealth required to obtain more than one wife.
The study is published in the October issue of Current Anthropology