Why do men have nipples?

nipples
If men can not feed the babies , why they have nipples? The answer comes from the hand of biology, on how humans we develop in the womb, as explained by the paleoanthropologist Ian Tattersall of the American Museum of Natural History in New York (EE. UU.)

The key is that all males and females, are built with the same genetic plan ; we develop in the womb slightly different way and especially after reaching puberty .

During the first few weeks, male and female embryos are exactly the same model, including the issue scheme covering us, the development of the nipples. However, at 6 or 7 weeks 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 produce testosterone , as it says in the book "Exploring the Biological Contributions to Human Health: Does Sex Matter "? (National Academies Press, 2001).

After formation of the testes , the male fetus begins to produce testosterone at 9 weeks gestation, changing the genetic activity of cells in the genitals and brain. But then, nipples, as we have seen, are already there, but subsequent human development make this vestigial structure is useless. Thus, the development of human beings explains why men have nipples .

The fact continue to count on this trail does not meet an evolutionary purpose is because t ener nipples is not harmful to men . There is no organic cost for their presence, hence continue although there 'are useless', biologically speaking.

Moreover, only because men do not need nipples all, is not so consistent evolutionary level to get rid of this trait reason. And it is that natural selection is not as pragmatic as we could imagine.