A new Northwestern University study of men in the Philippines makes a strong case for nurture’s role in male to female differences. For male infants, rapid weight gain in the first six months of life predicts a future where they will be taller, more muscled, stronger, have more sex partners and higher levels of testosterone than the average male.
The researchers, writing about their work in theProceedings of the National Academy of Sciences, speculate that testosterone may hold the key to understanding these long-term effects.
“Most people are unaware that male infants in the first six months of life produce testosterone at approximately the same level as an adult male,” said Christopher W. Kuzawa, author of the study. “We looked at weight gain during this particular window of early life development, because testosterone is very high at this age and helps shape the differences between males and females.”
Testosterone has long been known to increase muscle mass and put a person on a higher growth trajectory to be taller. This study suggests that the age of puberty is also influenced by events in the first six months of life. “Another way to look at it is that the differences between the sexes are not hard wired, but are responsive to the environment, and in particular to nutrition,” Kuzawa said.
Utafiti mpya wa Chuo Kikuu cha Northwestern wa wanaume nchini Ufilipino hufanya kesi yenye nguvu kwa jukumu la kulea katika tofauti za kiume na kike. Kwa watoto wa kiume, kuongezeka kwa uzito kwa haraka katika miezi sita ya kwanza ya maisha kunatabiri siku zijazo ambapo watakuwa mrefu, wenye misuli zaidi, wenye nguvu zaidi, watakuwa na washirika zaidi wa ngono na viwango vya juu vya testosterone kuliko wanaume wa kawaida. Watafiti hao waliandika juu ya kazi yao katika jarida la Proceedings of the National Academy of Sciences, na wanadhani kuwa testosterone inaweza kuwa ufunguo wa kuelewa athari hizi za muda mrefu. "Watu wengi hawajui kwamba watoto wa kiume katika miezi sita ya kwanza ya maisha hutengeneza testosterone kwa kiwango sawa na cha mtu mzima wa kiume", alisema Christopher W. Kuzawa, mwandishi wa utafiti huo. """Tuliangalia kuongezeka kwa uzito wakati wa dirisha hili maalum la maendeleo ya maisha ya mapema, kwa sababu testosterone ni ya juu sana katika umri huu na husaidia kuunda tofauti kati ya wanaume na wanawake."" - Testosterone imekuwa ikijulikana kwa muda mrefu kuongeza misuli na kuweka mtu kwenye trajectory ya ukuaji wa juu kuwa mrefu." Utafiti huo unaonyesha kwamba umri wa kubalehe huathiriwa pia na matukio katika miezi sita ya kwanza ya maisha. "Njia nyingine ya kuitazama ni kwamba tofauti kati ya jinsia si ngumu, lakini zinaitikia mazingira, na haswa lishe", alisema Kuzawa.