Friday Weird Science GUEST POST: Extra nipples – They’re just a matter of timing

Apr 01 2011 Published by under Friday Weird Science

For today's Dose of Friday Weird Science, I thought I could do something April Fools'y, but I've always thought that day was really pretty dumb. Instead, I have something MUCH BETTER. TODAY, Sci presents to you Brian Switek, of the Laelaps Blog over at Wired (Brian is also the writer of the Smithsonian's Dinosaur Tracking)! And, more pertinently, Brian is presenting you today with...HIS THIRD NIPPLE. With photos, or it didn't happen. As of now, he has not yet named the nipple. I am rooting for something like "Winston".

And while you're here, head over and congratulate Brian on getting a deal for his second BOOK!!! It'll be a retrospective on dinosaurs, and I think it will be awesome!!!

By Brian Switek

I have a third nipple. I don’t think about it much. It doesn’t bring me good luck or give me superpowers (as far as I know, anyway). It’s nothing more than a smaller version of its siblings that sits about two inches below my right nipple. Unless I’m standing shirtless in front of a mirror, I don’t even know it’s there.
But why is it there? I never bothered to find out. The dark-colored nubbin gives my chest some character, but if you asked me yesterday why it was there, I couldn’t say. After it popped up in conversation again a few months ago, though, I figured that I would see what I could find out about my superfluous nipple. Scicurious was kind enough to give me the perfect place to talk about it.

Extra breast tissue is fairly common and varies in placement and development in the people who have got it. There are two main categories – polymastia (accessory breasts) and polythelia (supernumerary nipples). The two are obviously related, but need not go together, and since I don’t carry an accessory boob – natural or otherwise – I’ll stick to extra nipples. (Wait, that didn’t sound quite right… Damn. Carrying on.)
Remember the villain Francisco Scaramanga from the 1974 James Bond flick The Man With the Golden Gun? Me neither – I never saw it – but Sci told me that the Bond foe had a third nipple, too. Wikipedia filled me in on the details. Unfortunately for Christopher Lee – who played Scaramanga – the make-up department just slapped on the prosthetic nipple wherever they thought it looked good, and it was a bit off-course.

(Figure 1: James Bond and his incorrectly placed nipple for the Man with the Golden Gun. Source)

My extra nipple falls along the milk line. That’s right where a third nipple should be. Way back when I was a six week old embryo these thickened lines of tissue began to develop on my body – running from the base of my arms and down across my chest before terminating at the upper thighs – but, instead of just creating a typical pair of nipples, an extra one developed on my right side. (I wish there was a better comparison for the extent of milk lines – and I warn you to specifically envision someone you think is sexy before finishing this sentence to avoid any unfortunate mental imagery – but the milk lines have roughly the same pattern as a slingshot thong, which, in truth, probably shouldn’t be worn by anyone, ever.) Scaramanga’s extra nipple was therefore a bit too far to the middle of his chest, which is a line I never anticipated writing.

Not all extra nipples fall along these lines. Extra nipples and accessory breasts – with and without nipples – have shown up on people’s faces, sides, backs, buttocks, feet, and elsewhere. Sometimes these become fully developed and lactate, and other times they don’t. In most cases, though, extra breast tissue develops somewhere along the milk line not far from the typical set of nipples.

In my case, the extra nipple is just the result of a small quirk of development. It’s not – as Charles Darwin once speculated – a sign that I am a partial throwback to some primeval mammalian state. Maybe I’m genetically part Neanderthal thanks to some rare Pleistocene romances, but my extra nipple, by itself, isn’t prehistoric.

(Figure 2: Mr. Switek's correctly placed third nipple)

Darwin first covered extra nipples and breasts in his 1868 book The Variation of Animals and Plants Under Domestication. (Thrilling title, I know.) Part of understanding variation – which was essential for his evolutionary mechanism of natural selection – was keeping track of exceptional cases. As far as extra breast tissue, Darwin thought symmetrical pairs of extra breasts in some women might be a “reversion” to what is seen in other mammals, and would therefore throw some unexpected support to the idea that we shared a deep ancestry with other mammals.

But Darwin later realized that his examples were cherry-picked. In a footnote included in 1871’s The Descent of Man, Darwin cited the observations of the German naturalist William Thierry Preyer that some breasts and nipples appeared off the milk line, therefore suggesting that extra breast tissue had some other cause. They could not be used as good evidence of our ancient mammalian past, leaving Darwin to lament “the force of my argument is greatly weakened or perhaps quite destroyed.”

Extra nipples may not be revisions to ancestral states, as Darwin had briefly speculated, but they do have a basis in an ancient, shared developmental pathway. Milk lines are a shared trait among many mammals and produce varying numbers of nipples in different places in diverse species. I wouldn’t call extra nipples true atavisms, but those along the milk line occur because of patterns of development that have been in place for tens of millions of years. Maybe I have Morganucodon or some other early mammal to thank for that.
As primates, though, our milk lines have been specialized to typically produce just two areas of symmetrical breast tissue, and an alteration in the timing of development can trigger the formation of extra ones. A 1995 review by Vic Velanovich states that it’s a simple matter of developing breast tissue not shutting off as expected. After the regular breast tissue develops along the milk lines, the ridges recede, and a delay in the regression causes extra nipples or breasts to form.

I’m glad I finally have some idea of my extra nipple’s origins. Not as exciting as being bitten by a radioactive spider, but, for a science geek, still pretty cool. My extra breast tissue may even be a little rarer than your average third nipple along the milk line. Velanovich stated that most extra nipples are found on people’s left side, and a small sample of twenty eight patients reported in 1998 also had extra nipples that were more common on the left side than the right. (A left/right ratio of 15/7 in males and 5/4 in females in a sample size of 28, meaning some individuals had extra nipples on both sides.) Not a terribly significant point, but interesting if your extra nipple is a rightie.

The trouble is that I don’t know what to do with this new information. “Hey, guess what I just learned about my third nipple?” isn’t exactly prime dinner conversation material. (Not when guests are over, at least.) An “Ask me about my third nipple” button wouldn’t really work, either. We spend so little time thinking about how to came to be as we are. I’m glad a little hiccup in my own early development gave me a reason to look into what makes me who I am.

Grossl NA (2000). Supernumerary breast tissue: historical perspectives and clinical features. Southern medical journal, 93 (1), 29-32 PMID: 10653061
Velanovich V (1995). Ectopic breast tissue, supernumerary breasts, and supernumerary nipples. Southern medical journal, 88 (9), 903-6 PMID: 7660204
Schmidt H (1998). Supernumerary nipples: prevalence, size, sex and side predilection -- a prospective clinical study. European journal of pediatrics, 157 (10), 821-3 PMID: 9809822

Darwin, C. 1868. The Variation of Animals and Plants Under Domestication. Vol. II. London: John Murray. p. 57
Darwin, C. 1871. The Descent of Man and Selection in Relation to Sex. London: John Murray. p. 125.

17 responses so far

  • Gillian B says:

    But what a horrid thought - getting your nipples pierced is now 50% more expensive???

  • Not Michelle says:

    Everyone I know who has an extra nipple (including myself) has it on the right side. I wonder if that is anecdotal or represents an actual trend, and if so, why?

  • Mike Keesey says:

    Since nipples are a therian feature, not mammalian (monotremes primitively lack nipples), I wouldn't expect stem-mammals like Morganucodon to have them. Maybe a stem-therian like Peramus? (I suppose the lines of development could have originated earlier, though.)

    • Brian Switek says:

      Thanks for catching that Mike. As you said, phylogenetic bracketing would suggest that nipples are a therian feature, but can we take monotremes as an example of the ancestral state? They are probably better models since they branched off earlier, but obviously we can't be sure. Likewise, I am curious whether monotremes have milk lines or some similar developmental pathway that was a precursor to what's seen in therians.

  • khan says:

    I have an extra nipple in my left armpit; makes shaving fun.

  • alice says:

    I love this so much. My mum has a third nipple, she delights in telling everyone that she didn't realise till she started lactating when she had me.

    I have different coloured eyes. If Brian ever wants to start a sci writing coven of THOSE WHO SHOULD BE BURNED.

  • EMJ says:

    I represent one of the few who has witnessed this "in the flesh" as it were (though how that came to pass will remain mysterious). Great to see the little feller get some media attention finally.

  • Martin says:

    As long as we're keeping count, my third nipple was on the left, exactly where it should (statistically) be. Sadly, it was a casualty of some other surgery I had in that area, and I now have only the usual two nipples in the standard location(s).

  • Tom says:

    Thanks for writing this. As it happens, I have 5 extra nipples, two (right and left sides) up by my shoulders, small, and not really developed, one more fully developed under my left nipple, and two more smaller ones (L and R side) down by my waist.

    Always thought it was a little strange, but no one seems bothered by it, and I've never been asked why im that way either.

  • claire says:

    Cool to know i always wondered about my extra nipples i also have four nipples one right side and one left side so does that make me double sided.. haha thanks for writing!

  • Anonymous says:

    I have 2 extra if anyone can tell me how to remove I'd like that so about my extras one on each side left and right. My right one is closer to my actual nipple and the left is further away it really disturbs me that my mother probably realised this but didn't do anything about it.

  • Koichi Ito says:

    I have heard that celebrity like Joanna Krupa and Lily Allen has extra nipples. But I saw a woman with 9 nipples on Dr. Mehmet Oz Show. And in fact I have 6 nipples in each armpit?

  • destiny says:

    I technically have four nipples. two under each breast. my mom an niece have the same thing. it's weird.

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