Men have nipples because of gestational economy.
Dear Matthew Alice: I’ve heard that a woman who is not pregnant can produce breast milk, but it takes many months of preparing the breasts. Is it possible for men to breast-feed as well? If not, then why do men have nipples? — Sherry Valencia, [email protected]
Your second question reappears regularly in the Matthew Alice compostal heap of queer-ies, and we floated one possible answer here in the not-so-distant past. Your first question, though, is a whole different beast, so I figured I’d try squeezing a few more column inches out of it.
According to UCLA physiologist Jared Diamond, in Discover magazine, anyone willing to do a little tinkering with hormones can get milk out of all kinds of things: kangaroos, steer,, male goats and guinea pigs, nonlactating women, and human males. The only male mammal that seems to develop enlarged mammary glands and lactate spontaneously under normal conditions is the Dayak fruit bat. (This discovery is new, and unfortunately Diamond offers no more details. Like why they’d bother.)
All male mammals have at least the basic plumbing needed to nurse an infant. The only thing missing is a sufficient quantity of the hormone prolactin (for humans; it goes by other names in other mammals). Those darned experimenters, who just can’t seem to leave well enough alone, have injected prolactin into patients being treated with estrogen as a cancer therapy. The double whammy of female hormones generated enlarged breasts and milk in the men. Starvation also stimulated breast enlargement and milk production in some World War II POWs. Medical speculation is that glandular systems shut down under these extremes. When they return to normal, the liver, which destroys hormones, recovers more slowly than the glands that produce lactation-related hormones, so they’re free to build up and circulate for a while.
I can’t imagine that the sample in this next study was very large, but lactation has been observed in certain surgery patients being treated with tranquilizers that affected the hypothalamus, as long as the surgery stimulated the nerve endings related to suckling an infant. Many species of female mammals (including humans) will produce milk if their nipples are stimulated sufficiently, since this releases lactation hormones. It also releases the hormone in the human male, so Diamond speculates that this is another way to produce lactation in men. The theory is unproven. Apparently the science guys haven’t found enough willing subjects to test it, or maybe they just can’t find anybody to fund a grant proposal for experimental nipple-tweaking. Make the NEA look like kindergarten; Congress would have a field day. Perhaps you Alicelanders would like to do your own tests.
None of this should lead you to the conclusion that men have nipples because they need them now or needed them in the past. In fact, no lactating male of whatever species (except presumably that odd fruit bat) has produced nearly as much milk as can a female. Male nipples are probably the result of a sort of gestational economy and efficiency. All human embryos develop from common tissue structures during early gestation. When the fetus is differentiated by sex, the common tissue is modified into “male” and “female.” So boys and girls at birth, with one notable exception, look pretty much alike. In the case of mammary tissue, female hormones at puberty enlarge the breasts to prepare them for lactation. Lacking those hormones, men’s breast tissue just sits there. Not very decorative, not very useful. As Stephen Jay Gould says, men have them because women need them. And with that, I think we’ve milked this topic for about all we can.
Anonymous in faxland contributes this to the growing files in our archive of famous body parts. In this case, it’s Revolutionary War naval hero John Paul Jones, and it’s all his parts. When he died in Paris in 1792, the French buried him in a coffin filled with alcohol in case we wanted his preserved remains back one day. Somehow, it took 100 years for anybody to remember he was there. But when they exhumed him for shipment back to Annapolis, he was pickled like a gherkin and nearly as good as new.