Men experience a drop in testosterone after the birth of their children, a phenomenon that may help them meet the challenges of caring for their offspring, said a study released on Monday.
Testosterone is a hormone that fuels male sexuality, aggression and physical robustness, and is typically highest in young, single men with no children, said the research in the Proceedings of the National Academy of Sciences.
With less testosterone coursing through their veins, men are more likely to adopt fatherly roles and help nurture their children, a particular need among humans who have much longer dependent childhoods than other mammals.
"Raising human offspring is such an effort that it is cooperative by necessity, and our study shows that human fathers are biologically wired to help with the job," said co-author Christopher Kuzawa of Northwestern University in Illinois.
The research was based on 624 men, age 21-26, in the Philippines who were tracked for nearly five years -- a period in which some of them entered stable relationships and became new fathers.
Of those who started the study single and became fathers by the end of it, the men with the highest initial testosterone levels were more likely to have become dads.
This distinction was important because previous studies had not been able to establish whether a testosterone dip observed in newly married men was a trait that made men more likely to marry, or if it resulted from the act of partnering.
"The men who started with high testosterone were more likely to become fathers, but once they did, their testosterone went down substantially," said co-author Lee Gettler, a doctoral candidate in anthropology at Northwestern.
"Our findings suggest that this is especially true for fathers who become the most involved with child care."
Men who became fathers during the study showed a median 26 to 34 percent drop in testosterone levels, which was significant compared the normal age-related decrease seen in single men who were not fathers (12-14 percent).
The steepest declines were seen in fathers of newborns, one month old or younger.
"Fatherhood and the demands of having a newborn baby require many emotional, psychological and physical adjustments," Gettler said. "Our study indicates that a man's biology can change substantially to help meet those demands." (AFP)
<한글 기사>
좋은 아빠일수록 남성 호르몬 빨리 감소한다
"아이 낳으면 가족에 헌신"하는게 '자연의 순리'
아버지가 되면 남성 호르몬인 테스토스테론이 감소하는 것으로 나타났다.
미국 노스웨스턴대학의 리 게틀러 박사 연구팀은 1983∼1984년에 출생한 필리핀 세부섬의 남성 600명을 대상으로 조사해 이 같은 결과를 얻었다고 뉴욕타임스(NYT) 가 13일(현지시각) 보도했다.
연구팀은 이들을 대상으로 독신이었던 21세 때와 5년 뒤인 26세 때의 테스토스테론 수치를 비교한 결과, 아이가 있는 남성은 아이가 없는 남성보다 호르몬이 두 배 이상 빨리 감소한 것으로 나타났다고 밝혔다.
특히 조사 대상 중 놀이, 독서, 목욕 등을 통해 하루 3시간 이상 아이들을 돌본 남성들의 호르몬 수치가 가장 낮았다고 연구팀은 덧붙였다.
나이가 들면서 남성 호르몬의 수치가 떨어지는 것은 자연스러운 현상이지만, 아 이를 낳고 육아에 관심이 있는 좋은 아빠일수록 남성 호르몬 감소 속도가 빨라진다는 것이다.
게틀러 박사는 "테스토스테론이 감소하기 때문에 남성들이 아이를 돌봐서는 안 되다는 의미가 아니라, 생물학적으로 여성만 부모가 되도록 적응하는 게 아니라 남성 역시 좋은 부모가 돼야 한다는 자연의 순리를 보여주는 것"이라고 조사 결과의 의미를 설명했다.
다른 전문가들도 이번 조사 결과가 남성의 호르몬 체계도 일단 아이가 태어나면 가족들에게 헌신하도록 진화됐다는 것을 보여준다고 말했다. (연합뉴스)
