Faster Growing Baby Boys Have More Sex as Men

Male babies that rapidly put on weight during their first six months will likely wind up having more sex when they reach young adulthood.

Researchers reported their conclusions today in the Proceedings of the National Academy of Sciences.

Based on their survey tracking more than 700 men from birth to early adulthood in the Philippines, the researchers said that this set of males reached puberty earlier. It also found that as young adults, they had higher testosterone levels and tended to be taller, more muscular, and possessed higher grip strength.

"They also had sex earlier and were more likely to report having had sex in the past month, resulting in more lifetime sex partners," the paper reports. However, the researchers were unable to find evidence of similar links in female subjects.

Although biologists have previously established links between babies' pre-natal adaptation and subsequent behavior as adults, today's findings elicited some skepticism in scientific circles. For instance, speaking with Science Now, Peter Ellison of Harvard University offered an alternative explanation to the proposed link between these boys' rapid maturation and their adaptive response later on in life.

The differences in growth rates could reflect genetic traits inherited from parents that influence how sensitive different boys are to testosterone, for example, which would make them grow faster and stronger. Regardless, Ellison says this is a very "rich" result that suggests many angles of new research, such as testing whether levels of testosterone in newborns, really influence rates of weight gain.