Male lactation
Encyclopedia
Male lactation
in zoology means production of milk from mammary gland
s 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 and not considered male lactation.
Male lactation was of some interest to 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.
, notably the Dayak fruit bat
(Dyacopterus spadiceus), and the lactating males may assist in the nursing
of their infant
s. In addition, male goats are known to lactate on occasion.
Lactation
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
in zoology means production of milk from mammary gland
Mammary gland
A mammary gland is an organ in mammals that produces milk to feed young offspring. Mammals get their name from the word "mammary". In ruminants such as cows, goats, and deer, the mammary glands are contained in their udders...
s in the presence of physiological stimuli connected with nursing infants. It is well documented in the Dayak fruit bat
Dayak Fruit Bat
The Dayak fruit bat or Dyak fruit bat is a relatively rare frugivorous megabat species found only on the Sunda Shelf of southeast Asia, specifically the Malay Peninsula south of the Isthmus of Kra, and the islands of Borneo and Sumatra. There are three species in the genus Dyacopterus: D....
.
The term male lactation
Lactation
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
is not used in human medicine. It has been used in popular literature to describe the phenomenon of male galactorrhea
Galactorrhea
Galactorrhea or galactorrhoea is the spontaneous flow of milk from the breast, unassociated with childbirth or nursing.Contemporary Maternal-Newborn Nursing Care defines galactorrhea as "nipple discharge." -Causes:...
which is a well documented condition in humans.
Newborn babies of both sexes can occasionally produce milk, this is called neonatal milk and not considered male lactation.
Male lactation was of some interest to Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
, who commented on it in The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex is a book on evolutionary theory by English naturalist Charles Darwin, first published in 1871. It was Darwin's second great book on evolutionary theory, following his 1859 work, On The Origin of Species. In The Descent of Man, Darwin applies...
(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 shewn by their occasional sympathetic enlargement in both during an attack of the measlesMeaslesMeasles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
."
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
Many male mammals have been observed to lactate under unusual or pathogenic conditions such as extreme stress, feeding castrated animals with phytoestrogens or animals with pituitary tumors. Hence it was hypothesized that while most mammals could easily develop the ability to lactate this does not provide the males, or the species with any evolutionary advantage. While the males could in theory improve the chance to pass on their genes by improving the feeding their offspring by male lactation, most of them have developed other strategies such as mating with additional partners. Presently only 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 other speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, notably the Dayak fruit bat
Dayak Fruit Bat
The Dayak fruit bat or Dyak fruit bat is a relatively rare frugivorous megabat species found only on the Sunda Shelf of southeast Asia, specifically the Malay Peninsula south of the Isthmus of Kra, and the islands of Borneo and Sumatra. There are three species in the genus Dyacopterus: D....
(Dyacopterus spadiceus), and the lactating males may assist in the nursing
Breastfeeding
Breastfeeding is the feeding of an infant or young child with breast milk directly from female human breasts rather than from a baby bottle or other container. Babies have a sucking reflex that enables them to suck and swallow milk. It is recommended that mothers breastfeed for six months or...
of their infant
Infant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
s. In addition, male goats are known to lactate on occasion.
Human male lactation
The phenomenon of successful human male breastfeeding has been credibly observed in several cases. However, the cases are not sufficiently documented to allow distinguishing of possible pathologic galactorrhea.Sources
- Angier, Natalie; New York Times, February 24, 1994. 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. Pyle