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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, such as Louise Erdrich's ''The Antelope Wife,'' 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,〔 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.〔Descent of Man, Chapter VI〕 ==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 pituitary tumors. 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 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Male lactation」の詳細全文を読む スポンサード リンク
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