Why Do Men Have Nipples, Anyway?

Men’s nipples do not serve a vital function.
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There is a logical explanation about why women have nipples: to feed babies. But why do men's bodies retain what appears to be redundant body parts? The Darwinian natural selection process would seem to dictate that male nipples really should not be there. So what's the deal? Why do men have nipples?

Why Men Have Nipples

As embryos in the womb, males and females have similar tissues and body parts. In fact, all embryos start out as female, which is why nipples are present in both sexes.

In boys, the Y chromosome and the hormone testosterone bring about changes to the embryo, including the growth of the penis and testicles. However, because the nipples have already developed before the sex of the baby is determined, the nipples stay. These vestigial nipples have no functional use.

Men and Breast Cancer

Believe it or not, male breasts can produce milk and are prone to breast cancer. That's because a certain level of the female hormone estrogen is present in all men. Sometimes, as a result of disease or a condition affecting hormones, breast tissue in men can grow (a condition called gynecomastia) and men can produce breast milk.

Gynecomastia is more commonly seen in adolescence, a period in development when hormones fluctuate a lot. It is also seen in some men with liver disease and sometimes in alcoholics.

Other 'Useless' Body Parts

Organs that have become functionless due to evolution are called "vestigial organs," and we have quite a few.

So what are some other seemingly useless body parts? Here are a few that you would have thought would have been victims of evolution:

Foreskin: Many men from different cultures all over the world have their foreskin removed during circumcision. In the past, the foreskin served to protect the penis from infection.

However, in the modern day when humans are fully clothed from birth, this is less important, and there is some evidence that an intact foreskin can actually harbor infection.

Eyebrows: While your eyebrows play a significant role in your appearance, have you ever wondered what they're actually doing up there on your face? At one point, our prehistoric ancestors probably had hair covering their entire face. While experts aren't exactly sure why the patches of hair above the eyes remained, eyebrows do serve to keep moisture out of the eyes from rain or sweat.

Wisdom Teeth: If most people just wind up having to have them surgically removed, why do humans have wisdom teeth? The wisdom teeth are really just our third set of molars, and our ancestors relied on them to eat coarse, rough food such as leaves, roots, nuts, and meats. Now that our modern diet is softer and we have more tools at our disposal to make consuming tough food easier, the wisdom teeth aren't necessary. Instead of growing in and helping us eat, many people's wisdom teeth instead stay put within the jaw and can push up against other teeth, causing problems that warrant their removal.

Other extraneous body parts include armpit hair, the appendix, and the tonsils, all of which can be removed without any impact on body function.

Sources:

Braunstein GD, Anawalt BD. Clinical features, diagnosis, and evaluation of gynecomastia in adults. In: UpToDate. 2017.

Gradishar WJ. Breast Cancer in Men. In: UpToDate. 2017.

Wilcox D. Care of the uncircumcised penis. In: UpToDate. 2017.

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