If men can’t feed babies, why do they have nipples? The answer comes from the hand of biology, on how human beings develop in the womb, as explained by the paleoanthropologist Ian Tattersall of the American Museum of Natural History in New York (USA).
The key is that all of us, males and females, are built with the same genetic blueprint ; In the uterus we develop slightly differently and especially after reaching puberty.
During the first weeks, male and female embryos follow exactly the same model, a scheme that includes the topic that covers us, the development of the nipples. However, at 6 or 7 weeks of gestation, a gene on the Y chromosome induces changes that lead to the development of the testes, the organ that produces and stores sperm and produces testosterone , according to the book “Exploring the Biological Contributions to Human Health: Does Sex Matter? “ (National Academies Press, 2001).
After the formation of the testes, the male fetus begins to produce testosterone at 9 weeks of gestation, changing the genetic activity of cells in the genitals and brain. But by then, the nipples, as we have seen, are already there, although their later human development renders this vestigial structure useless. Thus, human development explains why men have nipples.
The fact that we continue to have this trace that does not serve an evolutionary purpose is because having nipples is not harmful for men . There is no organic cost for their presence, hence they are still there even though ‘they are useless’, biologically speaking.
Also, just because men don’t need nipples at all is not an evolutionarily consistent reason to shed this trait. And it is that natural selection is not as pragmatic as we might imagine.
