Men l Testosterone and the Evolution of Fatherhood
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by Lisa Catherine Brown
Studies Link Fatherhood to Low Testosterone Levels
News outlets and bloggers alike have been reporting on new study results that link fatherhood to a drop in testosterone in men. The study conclusions answer some of the questions raised from previous studies that determined men who were fathers had lower testosterone levels than their single counterparts.
One of the dispelled notions was that men with lower testosterone levels were more likely to become fathers. The opposite proved true; men with higher testosterone levels were more likely to find a mate and become fathers.
The study led by Lee Gettler, Northwest University biological anthropologist, and his colleagues researched 624 men in the Philippines whose testosterone levels were measured over a five-year span.
The t-levels in men who remained single and without children remained stable but for those who became fathers the levels dropped dramatically - about in half - right after the birth of a child. The testosterone levels in the new fathers then rebounded but in varying amounts.
Men actively involved in caring for and spending three hours or more a day with their children remained at lower testosterone levels than uninvolved fathers. “There’s something about being an active father that’s contributing to these dramatic declines,” Lee Gettler, the NU study leader says, “There’s something that’s going on in their first months that’s helping them transition to their role as fathers.”
An article in the Los Angeles Times notes another study by Peter Ellison, an evolutionary biologist at Harvard University who was not involved in the current study.
Ellison pointed to a 2008 paper he co-wrote in which he and colleagues documented the very different parenting styles of men in two neighboring groups living around Lake Eyasi in northern Tanzania, the Hadza and the Datoga.
Hadza men were ideal fathers in many ways, Ellison said: They carried, cleaned, fed and pacified their infants and slept around the same hearth as their children.
The Datoga, on the other hand, considered child-rearing to be women’s work, so they rarely interacted with their infants and slept and ate separately from their wives.
Those opposing views of fatherhood were mirrored in the men’s hormones. The Datoga fathers’ testosterone levels were no different from their childless peers. Among the Hadza, however, fathers registered levels that were 30 percent lower in the morning and 47 percent lower in the evening than for men who weren’t raising children.
Ellison’s study of the neighboring groups was the first to show that a father’s role in child care was directly linked to testosterone production.
Beneficial Outcomes
The evolution of men into active fatherhood roles can also have health benefits – Christopher Kuzawa of the NU study is quoted in a VOA News article, “Having high levels of testosterone can increase your risk for diseases like prostate cancer [and] testicular cancer. Also, testosterone can suppress the immune system so that you’re less capable of fending off pathogens.”
This in itself may be a evolutionary response for fathers caring for young children whose immune systems are less developed and more vulnerable.
In an article posted in Health News on healthfinder.gov more questions are raised warranting further study. Robert J. Quinlan, associate professor of anthropology at Washington State University, suggests whether testosterone levels don’t drop in men who end up having poor relationships with their children. “One might manipulate the system by encouraging fathers to get the early experience with children that lowers testosterone levels, and then perhaps family stability and child outcomes would improve,” he said.
So for now, news writers and bloggers will continue to consider the implications of the study – are we talking manliness vs. fatherhood or fatherhood equals manliness? The simple conclusion may well be as Ellison suggests in the LATimes, “We’ve evolved to be good fathers.”
The study is published online in the Proceedings of the National Academy of Sciences.
Related reading:
Male Mice Brains Grow After Touching Their Babies
One of the most interesting stories about men’s lives in the last few decades is the importance of relationships with their children. Many a man has demonstrated himself to be a darn good parent and sometimes better than mom.
Neuroscientist Samuel Weiss, PhD, director of the Hotchkiss Brain Institute at the Faculty of Medicine, has demonstrated that paternal lab mice that physically interact with their babies grow new brain cells and form lasting memories of their babies. The study is published online in the journal Nature Neuroscience.
Specifically, new brain cells develop in the olfactory bulb, the part of the brain responsible for sense of smell, and in the hippocampus, which is responsible for memory. Weeks later, after separation, the father mice who bonded with their offspring continue to recognize them.
Among father mice who didn’t bond physically with their babies, no new neurons were grown and they couldn’t recognize their offspring weeks later. via Science Daily
New Dads Suffer From Postpartum Depression, Too
Researchers from Eastern Virginia Medical School in Norfolk, Va analyzed 43 studies involving over 28,000 men and concluded that about 10 percent of new fathers experience the equivalent of postpartum depression. Three months after the birth, researchers estimate that 25 percent of new fathers are depressed.
In general, 10-30 percent of new mothers are depressed.
Researchers have usually associated postpartum depression with the changing hormones surrounding birth. But more and more researchers have noted that the lack of sleep, the increased stress and family strain associated with the little bundle of joy are classic triggers for depression. Read on at ABC News
