The Science of Sex: A Nipple Too Far

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A Nipple Too Far

You’d think that a reasonably observant fifty-six year old, such as myself, would know how many nipples he possessed. Until two weeks ago, I was sublimely confident that I had two. I didn’t have a shred of doubt about it. One on the left side of my chest, and one on the right side. Grand total: two.


This reassuring self-image began to fall apart, however, when the topic of “supernumerary nipples” came up on a sexologists’ mailing list I belong to. “Supernumerary” means “extra.” If you need to ask why doctors replaced a simple word like “extra” with a hexasyllabic tongue-twister like “supernumerary,” you know nothing about the medical profession. Just be thankful they say “nipples,” not “galactophoric peduncles.”


According to one expert on the list, supernumerary nipples don’t have to be very nipple-like. Many are just small patches of reddish-brown skin, like the “areolar” skin around the regular nipples. The surface is often rough but there may be no central promontory. They could easily be mistaken for a large freckle or mole. And there can be one or more of them. What matters is location: extra nipples are found on the “milk lines.” These lines start in the armpits, curve forward through the location of the regular nipples and then descend obliquely to the inner part of the groin.


The mailing-list expert mentioned that poster-boy Marky Mark Wahlburg has such an appendage, and gave the web address for some photos of the buff actor in the buff. I am always happy to check out Marky Mark’s body, so I jaunted over to the site. Yes indeed, there was a large fleck or freckle, an inch or two below and an inch inboard from his left “regular” nipple. And a dermatologist attested that this was indeed a supernumerary nipple. Then I looked down at my own body and, to my amazement, found that Mark and I had identical packages — in the nipple department, at least. Like him, I have three.


I had barely absorbed this fact when another subscriber to the list came up with a bunch of references concerning the genetics of supernumerary nipples. At least some are inherited, it turns out, and they are inherited in an “autosomal dominant” fashion. This means that a parent (of either sex) passes the trait on to about half of his or her children. So I sent a “nipple alert” to the LeVay clan back in Olde England. I quickly heard back that I have a brother and a niece with extra nipples, too. My father found none on himself, and recalled none on my late mother. But my father’s second wife wrote me that she had one, and so did her late sister and mother. That’s strange, I thought — was I switched at birth?


It turns out, however, that extra nipples are quite common. About one in twenty people have them in the same modest form that I and my stepmother do, so the coincidence could easily be exactly that — a coincidence. The better-developed, nipple-like nipples are much rarer. But they may be more common in some populations. One subscriber to the mailing list, a doctor who worked two years on a Navajo reservation, said that he saw them commonly on Navajo women. In these women, they were located in the armpits.


Extra nipples are thought to be an evolutionary throwback. But how far back, exactly? Primates in general have only two nipples. We have to go back several tens of millions of years, to the common ancestors of primates and other mammals, to find species with rows of nipples, as we now see in pigs, cats and dogs. But primates clearly “remember” the milk line. It is evident in embryonic development, and it is also evident in the location of the regular nipples. Whereas humans and most primates have their two nipples near the top end of the milk line, a few primates, like the endangered aye-aye of Madagascar, have them at the bottom end, in the groin. Like cows.


Finally, some FAQs about supernumerary nipples:

  • Do extra nipples secrete milk? Not usually, but entire extra breasts, capable of milk secretion, do sometimes crop up.
  • Are extra nipples unhealthy? Not usually, but any associated breast tissue is liable to the same diseases as regular breast tissue. There is a rare genetic association between extra nipples and some forms of kidney disease.
  • What’s the most number of nipples a person can have? The most I’ve seen reported is ten — all with associated breast tissue. This case was described in 1882.
  • Are extra nipples erogenous? Not in my experience. Perhaps readers will weigh in with more information on this score.
  • Are extra nipples lucky or unlucky? Lucky.