Production of milk (lactation) from a male mammal's is well-documented in the dayak fruit bat and the Bismarck masked flying fox. The term "male lactation" is not used in human medicine. It has been used in popular literature, such as Louise Erdrich's The Antelope Wife, to describe the phenomenon of male galactorrhea, which is a human condition unrelated to childbirth or nursing. Newborn babies of both sexes can occasionally produce milk. This is called neonatal milk (also as "witch's milk") and not considered male lactation.
History
Male lactation was of some interest to Alexander von Humboldt, who reports in
Voyage aux régions équinoxiales du Nouveau Continent about a citizen of the Venezuelan village of Arenas (close to
Cumana) who allegedly nurtured his son for three months when his wife was ill,
[
Voyage de Humboldt et Bonpland; 1-3. Voyage aux régions équinoxiales du Nouveau Continent : fait en 1799, 1800, 1801, 1803 et 1804. Tome 1 / par Al. de Humboldt et A. Bonpland; rédigé par Al. de Humboldt; J. Smith (Paris), 1814-1825, p. 376, (Online at gallica)] as well as
Charles Darwin, who commented on it in
The Descent of Man, and Selection in Relation to Sex (1871):
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.
Evolution and biology
Male mammals of many species have been observed to lactate under unusual or pathogenic conditions, such as extreme stress, castration, and exposure to
phytoestrogens, or
. Therefore, it is hypothesized that while most male mammals could easily develop the ability to lactate, there is no selective advantage to male lactation. While male mammals could, in theory, improve their offspring's survival rate through the additional nourishment provided by lactation, most have developed other strategies to increase the number of surviving offspring, such as mating with additional partners. Presently, very few species are known where male lactation occurs and it is not well understood what evolutionary factors control the development of this trait.
Nonhuman animal male lactation
The phenomenon of male lactation occurs in some species, notably the dayak fruit bat (
Dyacopterus spadiceus), lesser short-nosed fruit bat (
Cynopterus brachyotis), and the Bismarck masked flying fox (
Pteropus capistratus). Lactating males may assist in the
Breastfeeding of their infants. In addition, male goats are known to lactate on occasion.
Human male lactation
Spontaneous production of milk not associated with childbirth, known as
galactorrhea, can occur in human males and females.
Case reports of lactation induced in transgender women have been published.
See also
Citations
Sources
-
Cr. J. Covey, Francis, Charles M., et al.; "Lactation in Male Fruit Bats," Nature, 367:691, 1994.
-
Fackelmann, K.A.; Science News, 145:148, 1994.
-
Anomalies and Curiosities of Medicine G.M. Gould and W.L. Pyles
External links
