The Reason Men Have Nipples

Ok, explaining that mysterious phenomenon isn’t the main thrust of this article at Scientific American‘s site, which claims that men are biologically at risk because of the way male bodies develop in the womb. But the article suggests there’s a reason men have those things on their chests that aren’t very useful:

The male’s problems start in the womb: from his more complicated fetal development, to his genetic makeup, to how his hormones work.

The nine-month transformation from a few cells to an infant is a time of great vulnerability. Many chronic illnesses are seeded in the womb. In our species, the female is the default gender, the basic simpler model: Humans start out in the womb with female features (that’s why males have nipples). The complicated transformation in utero from female to male exposes the male to a journey packed with special perils.

When the first blast of testosterone from the Y gene comes along at about the eighth week, the unisex brain has to morph into a male brain, killing off some cells in the communication centers and growing more cells in the sex and aggression centers. The simpler female reproductive system has to turn into the more complex male reproductive tract, developing tissues such as the testis and prostate.

Further, it takes a greater number of cell divisions to make a male; with each comes the greater risk of an error as well as the greater vulnerability to a hit from pollutants.

On top of that challenge, the human male’s XY chromosome combination is simply more vulnerable. The two XXs in the female version of our species offer some protection: In disorders where one X chromosome has a genetic defect, the female’s healthy backup chromosome can take over. But with his single X chromosome, the male lacks a healthy copy of the gene to fall back on. The X chromosome, which never shrank, is also a larger chromosome “with far more genetic information than the Y chromosome,” finds … a University of California, Davis, autism researcher, “so there may be some inherent loss of key proteins for brain development or repair mechanisms in boys”…

Females also have a stronger immune system because they are packed with estrogen, a hormone that counteracts the antioxidant process… Low estrogen even leaves boys more sensitive to head injuries. The male brain “is simply a more fragile apparatus, more sensitive to almost all brain insults.”

The article says that males have more premature births, worse reactions to environmental toxins, more asthma, higher infant mortality and more neurological disorders. The good news, assuming that men are necessary at all, is that the male Y chromosome seems to have stopped shrinking, after millions of years of decline.

I can’t vouch for the science in this article. But there must be some explanation for the statistical differences between males and females that the author describes.

Reading this reminded me of something I read years ago about boys facing a special psychological challenge as they grow up. Children generally start out feeling closer to their mothers than their fathers. At some point, however, boys have to deal with the fact that they are different from their mothers — they can no longer identify with their primary caregiver the same way girls can. I don’t remember what conclusions were drawn from this or who drew those conclusions. This difference between the sexes might not mean anything at all. Anyway, it looks like us guys have other things to worry about, starting in the womb.

2 thoughts on “The Reason Men Have Nipples

    1. Larry Post author

      I’m not sure what that statement about the female body being the “default” really means. Apparently, males and females have the same organs for about 9 weeks, then they start to change. If females stopped changing after 9 weeks, and males didn’t, you could certainly say that the female body is the default. Maybe what the statement means is that the testosterone arriving at around 9 weeks makes the male body goes through some changes over and above what the female body goes through.

      Reply

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