Study: Fathers Hard-Wired to Care for Offspring
By Susan Brinkmann, OCDS
Staff Journalist
A new study has found that a father's testosterone levels drop off significantly after their babies are born, which shows that human males are biologically wired to turn away from mating behavior and to focus on caring for offspring.
FoxNews.com is reporting that the research, which was conducted at Northwestern University, followed a group of 624 males aged 21.5 to 26 years old for 4.5 years in the Philippines and found that testosterone levels fell dramatically after the men found partners and became fathers.
This reaction is in keeping with other species in which males take care of dependent offspring. Higher testosterone levels are associated with mating behavior, something that can conflict with the responsibilities of fatherhood, which is why it is advantageous for the body to reduce production of this hormone for the benefit of the offspring.
"Men are, to a certain degree, hardwired to take care of their kids," study researcher Lee Gettler, of Northwestern University in Chicago, Illinois, told LiveScience. "This is important because traditional models of human evolution have portrayed women as the gatherers that take care of the kids and stay behind."
But this study proves women weren't meant to shoulder these burdens alone. "Raising human offspring is such an effort that it is cooperative by necessity," said Christopher Kuzawa, co-author of the study, "and our study shows that human fathers are biologically wired to help with the job."
Previous studies had shown that fathers tended to have lower testosterone levels, but they were not conclusive regarding whether fatherhood diminished testosterone or whether men with low testosterone in the first place were more likely to become fathers.
Gettler said, "It's not the case that men with lower testosterone are simply more likely to become fathers. On the contrary, the men who started with high testosterone were more likely to become fathers, but once they did, their testosterone went down substantially."
This was especially true for fathers who decided to become more involved with child care. Once this decision was made, testosterone levels were found to drop even more. "Their bodies respond by saying, 'This is where we are focused now, we are focused on the kids,'" Gettler said.
The findings may also explain why finding a partner and becoming a father are good for a man's health and longevity. Some researchers believe testosterone lowers immune function: Higher testosterone levels may interfere with the immune system's ability to fight off infection. If this is true, lowering testosterone could be an investment in men's health.
The researchers, who plan to follow up with the same group of men at around age 30, published their findings in the scientific journal, Proceedings of the National Academy of Sciences.
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