Men could potentially breastfeed
Our DNA is made up of 23 chromosomes. Out of these, 22 are 100% the same DNA in both men and and women. The 23rd chromosome controls if you develop a penis or vagina (sexual dimorphism).
Foetuses start out the same, with the same sexual organs, then after four weeks the organs start to differentiate.
“The reproductive organs first develop in the same form for both males and females: internally there are two undifferentiated gonads and two pairs of parallel ducts”https://www.britannica.com/topic/human-sexual-activity/Development-and-change-in-the-reproductive-system
Most male mammals have nipples
Likewise, both male and female mammals develop nipples. Do you have a male cat or dog? take a look at their belly right now! There are a few exceptions such as mice, stallions and platypus. Male mice do start out with nipples, but the protein PTHrp removes them. Scientists have injected oestrogen or progesterone into male cows, goats and steers and succeeded in provoking lactation.
Boys and girls both have nipples and milk lines.
“Milk lines appear in the seventh week of embryonic development before human sexual differentiation, which explains why male humans have nipples. After initial development of the milk lines they go into remission.”https://en.wikipedia.org/wiki/Mammary_ridge
Nipples-wise, boys and girls have roughly the same setup until puberty. When they hit puberty, hormones such as oestrogen in girls cause breast growth and mammary gland development and that’s when things diverge.
Some babies lactate (both boys and girls), it’s called Witch’s Milk
The hormone prolactin facilitates breast milk production in new mums. Oestrogen regulates the production of prolactin in the pituitary gland. If a mother has too much oestrogen they can pass this along in utero to the foetus and the baby comes out with the ability to lactate (this is known colloquially as witch’s milk because, in folklore, they thought the witches came in the night and drank the milk of infants). Neonatal milk affects both boys and girls and typically lasts a couple of weeks. You should not milk the infant as it can prolong milk production.
Spontaneous milk production in fathers
It is more likely if the father has high oestrogen levels or problems with their pituitary gland leading to overproduction of prolactin.
Men with high oestrogen levels that trigger the release of prolactin can potentially produce milk.
The Sri Lanka widower who breastfed his baby
There are a few recorded cases of this happening in history. In 2002 Sri Lanka when a man’s wife died, he took over the breastfeeding of their baby. Mr B Wijeratne, from Walapanee, found that his daughter would not drink powdered milk. He found that he could breastfeed her.
After a baby is born, fathers experience a reduction of testosterone and an increase in oestrogen, thus prolactin. It is thought that as the father holds a baby to his chest it could trigger the production of milk as a physiological and biological response.
“Men with a hyperactive prolactine hormone can produce breast milk.”Dr Kamal Jayasinghe, Kurunegala Hospital, Sri Lanka. Sri Lankan widower learns to breastfeed
Hundreds of male prisoners spontaneously lactated
During the second world war in a Japanese POW camp, 500 men were found to be spontaneously lactating. This was because they were starving. When the pituitary gland produces prolactin, the liver removes these excess hormones, but when you’re starving neither of those organs work. However, as you recover, your pituitary gland recovers faster than your liver and so prolactin is not removed from the body, resulting in a build up which leads to lactation in starving men.
The ancient African tribe whose men suckle their babies
The Aka Pygmy tribe in Africa are known as the best fathers in the world. An Aka father typically spends 47% of their time within arm’s reach of their baby. In the Aka tribe, gender roles are interchangeable. sometimes the women go out to hunt and the men look after the kids. When Professor Barry Hewlett, an American anthropologist, went to study the tribe, he noticed that the babies were sometimes being suckled by their fathers.
Male nipples are vestigial
Much like the appendix, tailbone or wisdom teeth, nipples are vestigial. That means that they represent an evolutionary function that was once necessary for survival.
Just as men can lactate, they can also get breast cancer. In 2012 in the US, 2,200 men got breast cancer.
Bonus fact: Extra nipples
1 in 40 newborns has an extra nipple, normally men and on their left hand side. It is called polythelia.
Men breastfeeding in literature:
“Yes, but a man can’t nurse a baby,” said Pestsov, “while a woman….”Anna Karena, Tolstoy
“No, there was an Englishman who did suckle his baby on board ship,” said the old prince, feeling this freedom in conversation permissible before his own daughters.
It is possible, and has been observed in animals and humans. In 1992, 18 Dayak fruit bats were captured from a rainforest in the Krau Game Reserve, Pahang, Malaysia. Of the 10 mature males captured, each had functional mammary glands from which small amounts of milk were expressed. A breast is a breast. Male lactation is physiologically possible and, according to Dr. Robert Greenblatt, production in males can be stimulated by letting a baby suckle for several weeks. Indeed some human males secrete milk at birth and at puberty. Historically, male lactation was noted by the German explorer Alexander Freiherr von Humboldt prior to 1859, who wrote of a 32-year-old man who breastfed his child for five months. It was also observed in a 55-year-old Baltimore man who had been the wetnurse of the children of his mistress.Male Lactation” by Professor Patty Stuart Macadam of the Department of Anthropology at the University of Toronto (Compleat Mother, Fall, 1996, Volume 43).
Can men lactate and breastfeed babies naturally? – Qrius.com
Why Do Men Have Nipples? – By: Cristen Conger | Updated: Feb 12, 2021, How Stuff Works