On women they are multitaskers: suckling aids, an indication of sexual arousal, a work of art; on men they do little more than resemble mosquito bites and have no obvious function. The answer to the enigma of male nipples lies under the microscope.
In the first few weeks of development, each embryo is effectively bisexual. The base template for humans includes nipples, which continue to develop fully if the foetus gains female characteristics, and become redundant if the Y chromosome kicks in and testosterone starts pumping around the developing foetus. As it is more effective for the body to keep what has already been added than to remove parts, the nipples remain.
In fact, male nipples are not entirely redundant. They contain all the essentials of functioning organs and are connected to blood vessels, nerves and even milk ducts. Men do possess the milk-producing gland but this only develops if there are sufficient quantities of oestrogen present.
Some male babies contain an overdose of their mother’s oestrogen when born, causing them to lactate dramatically upon suitable stimulation. Rather than imagine why anyone would want to rub a baby’s nipples on the remote chance that milk might spurt forth, let’s leave this so-called phenomenon of “witches’ milk”.
It is not only newborn male babies who could rival Moo Moos for milkshakes, but also some grown men and teenagers. Gynaecomastia is the clinical term for abnormal enlargement of the breasts. While this might be every lads-mag fantasy, it’s not such a turn-on when it applies to men themselves.
Certain diseases or hormonal conditions, including many provoked by excess consumption of alcohol, can cause breast tissue to grow and men to lactate. In a particularly unsexy turn of evolution, it is teenage boys who most frequently suffer such a fate.
Redundant nipples are present in most male mammals, whilst in other genera, such as horses and mice, the male sex hormones completely prevent nipple growth. On the contrary, female possums are endowed with between seven and twenty five nipples, making our own two seem rather pitiful.
In fact, in the early stages of human development, up to seven pairs of nipples are arranged along a “milk line” running from the upper chest to the navel. Usually only one pair develops but aproximately one in a hundred people have a third mole-like nipple.
Why do men have nipples?
