Q: Nipples in Men...
Why do men have nipples?
David
Dr Trisha Macnair responds
Men not only have nipples but rudimentary breast tissue too. This means that they are at risk from breast cancer, although it is far less common than in women, and occasionally have other breast problems.
Like women, men's breasts are influenced by hormonal changes. In some circumstances, such as in liver disease, levels of female type hormones (oestrogens) may rise and the breasts may grow - a condition known as gynaecomastia.
In fact one of the peaks of my journalistic career was when I reported for the BBC on the unusual development of breasts by an American man. On holiday in the Caribbean, he had gorged on chickens which had been fed oestrogen-based growth promoters, while at the same time he was boozing wildly on tropical cocktails so wiping out his liver's ability to metabolise the hormones. The story finally made page 3 of The Sun!
Men can even make breast milk if their nipples are stimulated enough - I once saw a case of a man whose wife enjoyed nibbling his nipples during sex - to the point where the hormonal control system which produces milk was switched on. He eventually needed medication to turn it all off again.
But why?
After conception the developing embryo follows a female template. It is only after 6-8 weeks that the effect of a gene on the Y chromosome kicks in for boy embryos. This gene stimulates the production and influence of hormones such as testosterone which 'masculinise' the embryo by altering physical development to form male features.
But nipples are formed very early in the embryo, before this masculinisation process takes place, and nothing that goes on later in fetal development reverses nipple formation.
So the story that God made Eve from Adam's rib got it the wrong way round. Males are an adaptation of females and the nipples are just one piece of evidence of this.
Evolution may hold an answer
But why hasn't evolution meant that men have lost these nipples? Over the millennia the human body has been adapted and shaped by what makes one man more successful than another.
Having breasts and nipples - being able to suckle the young - may have conferred an advantage over those men who could not. For example it may have increased the chance of survival in lean times if the father could feed the babies as well as the mother. Conversely it doesn't seem to have been a disadvantage - nipple disease in men is very rare. Because nipples in men don't cause problems there is no genetic drive to lose them.
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If you saw two guys named Hambone and Flippy, which one would you think liked dolphins the most? I'd say Flippy, wouldn't you? You'd be wrong, though. It's Hambone.