Test this tos ter one

Marlene Zuk, professor of ecology, dvolution and behavior at the University of Minnesota, notes in her forthcoming book Paleofantasy: What Evolution Really Tells Us About Sex, Diet and How We Live that “conventional wisdom holds that men are unreliable long-term mates because they’re always questing for new partners, but “what if the urge to find a new mate is ameliorated by the experience of fatherhood itself?”

In a long-term study of 600 men in the Philippines, anthropologist Lee Gettler of Northwestern University measured the men’s testosterone and predicted those with higher testosterone levels at the start of the study would become “partnered fathers” by the follow-up, four and a half years later. And he was right.

“But then something interesting happened,” Zuk writes. “The fathers showed a dramatic decline in testosterone compared with both their own single, pre-paternal levels, as well as the levels of the men who had remained single. What is more, testosterone was lowest in those men who spent at least three hours a day caring for their son or daughter, after controlling for the effects of sleep loss and other variables.”

“This study is illuminating for several reasons,” Zuk writes. First off, the same men being re-measured, instead of fathers being compared to single men, allows for fewer variables. Second “it indicates a finely tuned back-and-forth between a person’s physiology and behavior. Cues from the environment can influence fathers’ hormone levels as well as those of mothers. The scientists suggest that while seeking a mate requires characteristics that may be antithetical to being a good father, it is, in fact, possible to have it all, and testosterone acts as the mediator.”

Finally, Zuk writes "As Peter Gray, an anthropologist at the University of Nevada, pointed out in a commentary accompanying the article, the research serves as a nice case study of the relevance of evolution to everyday human life. The trade-off between mating and parenting is one that is predicted by evolutionary theory, and it means that a longing for new sexual partners might not be part of our heritage.”