Male Lactation

Male lactation in zoology means production of milk from mammary glands in the presence of physiological stimuli connected with nursing infants. It is well documented in the Dayak fruit bat.

The term male lactation is not used in human medicine. It has been used in popular literature to describe the phenomenon of male galactorrhea which is a well documented condition in humans.

Newborn babies of both sexes can occasionally produce milk, this is called neonatal milk (also known as "witch's milk") and not considered male lactation.

Male lactation was of some interest to Alexander von Humboldt, who reports in Voyage aux régions équinoxiales du Nouveau Continent of a citizen of the village Arenas (close to Cumana) who allegedly nurtured his son for three months when his wife was ill, as well as Charles Darwin, who commented on it in The Descent of Man, and Selection in Relation to Sex (1871):

"It is well known that in the males of all mammals, including man, rudimentary mammae exist. These in several instances have become well developed, and have yielded a copious supply of milk. Their essential identity in the two sexes is likewise shown by their occasional sympathetic enlargement in both during an attack of the measles."

Darwin later considered the nearly perfect function of male nipples in contrast to greatly reduced structures such as the vesicula prostatica, speculating that both sexes may have nursed young in early mammalian ancestors, and subsequently mammals evolved to inactivate them in males at an early age.