Posted on: July 27, 2016 at 10:05 am
Last updated: September 13, 2017 at 11:36 am

Why Do Men Have Nipples? And Can They Breastfeed?

The first true mammals are thought to have started to walk the Earth some 210 million years ago, named as such from the Latin mamma meaning ‘breast’. Animals in this classification get their name because they feed their young with milk from their breasts.

Through many millennia, these first creatures evolved into the broad spectrum of mammal species we see today, including, of course, humans, and though the female of the species needs nipples to continue this vital milk delivery to her young, what’s the deal with male nipples?

Embryonic Development

why men have nipples

What this all essentially comes down to is that fact that for the first 8 or so weeks of development in the womb, male and female embryos develop identically. We are all built to a common blueprint. More specifically, we all develop to a female blueprint, before our chromosomes determine our sex as male or female. The gene for nipples is found in the X chromosome, which we all possess. Women having two, XX, and men holding both an X and a Y chromosome.

The formation of mammary glands and tissues begins very early on before any of the gender-specific processes take place. It is during these first weeks of embryonic growth, that we all develop a mammary ridge, or ‘milk line’, essentially a thickening of the skin running from the armpit to the thigh (think about the rows of nipples on other mammalian species.) In human development, this ridge pulls back and leaves us with nipples.

At around the 8th week of development, an embryo developing into a male will begin to secrete factors that block development of female structures in the body. It’s at this point that the Y chromosome kicks in and the embryo begins development into a male. The nipples, however, remain.

Why Hasn’t it Been ‘Written Out’ of Male Code?

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As humans we are the product of our parents, we all essentially copy one set of genes from our mother and one from our father, as such becoming a combination of traits from both parents. One could wonder how genders ever branch off if genes from both parents are inherited?

To answer this, consistent differences in males and females of the same species are common, but they only evolve if the same trait in males and females has become “uncoupled” at the genetic level. Uncoupling occurs if there is a reason for it; if the trait is important for the success of reproduction, but is different for a male and a female.

This is how you end up with birds of the same species, but different sexes, having plumages of different colors, for example. This uncoupling won’t occur if the attribute is important to both sexes, or if it is important to one sex, but unimportant to the other. Case in point (no pun intended) nipples!


For women, nipples are vital for the continuation of the human race; to breastfeed children, and seeing as for males, these nipples are merely unimportant – they don’t affect the continuation of the species either way – it doesn’t make sense for them to be eliminated.

If you’re still feeling confused, it is better to think of nipples as never having been selected against, rather than having been selected for.

Can Men Breastfeed?

Sorry for putting that image in your head, but if men have nipples, taking this to the logical conclusion, can they breastfeed? Male lactation isn’t actually that farfetched, and will usually happen soon after birth, in something referred to as ‘witch’s milk’. Prolactin, a hormone that facilitates breast milk production in new mothers, and can pass through the placenta into a baby’s body, causing it to spontaneously lactate after birth, though this usually stops after one or two weeks.

There have also been studies on adult male breastfeeding, and it was found that spending prolonged amounts of time with babies can increase levels of prolactin in fathers’ bloodstreams, and coupled with a suckling baby, this could very well lead to a male breast yielding milk though it is still uncommon. Unfortunately, breast cancer can also occur in men, though this only accounts for about 1% of breast cancer cases, so is incredibly rare.

Your Nipples Have a Lot of History


So if you’re female, you probably already knew the importance of your nipples, but if you’re male, you can now look down and feel proud in the knowledge of the rich evolutionary history behind your nipples, and in the knowledge that you were once female, even if only for a couple of months.

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