Once a human embryo has been conceived, no matter what its ultimate gender, it follows a female template,adopting all female characteristics, including nipples After a number ofweeks in this state, a certain gene in the male embryo stimulates the production of the male hormone testosterone,which prompts the embryo to develop masculine qualities While the nipples remain present (because they are formed before this process takes place), they will not function in theway that they would have had the embryo been supplied with female hormones.
Not only do male babies have nipples, but they are also born with breast tissue and milk ducts and glands These are normally inoperative, but, if men experience increasedlevels of the female hormone estrogen and a lack of testosterone,they can develop breasts like those of women and,in extreme cases, even perform lactation Because men have breast tissue, they are at risk from breast cancer, albeit to afar lesser extent than women are.
It is thought by some that men might once have used nipples to help feed their young during lean times Now that this no longer occurs, ithas been asked of scientistswhy evolutionhas not done away with these superfluous malenipples The commonresponse is that, becausediseases affecting the nipples are rare in men, there is no genetic imperative todo away with the nipples, and so they simply remain.
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