I found a link that sums up this thread very neatly,
and what most of the members have posted is true.........
The phenomenon of male lactation in humans has become more common in recent years due to the use of medications that stimulate a human male's mammary
gland.(milk-secreting organ of female mammals) It is common knowledge that human males have nipples. It is not so often understood that they also have
mammary glands. Ordinarily the mammary tissue is low in volume and cannot be noticed. Under the appropriate hormonal stimulus, the mammary glands of
human males can also produce milk.The volume of milk produced will be small relative to the amount that a female can produce.
The most common circumstance under which lactation is induced is when hormonal treatments are given to men suffering from prostate cancer.
The secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effecthormones are used to retard the
production of cancerous prostate tissue, but the same hormones also stimulate the mammary glands.
(A person whose sexual identification is entirely with the opposite sex) Transsexuals may also produce milk due to the hormones they take to reshape
Has also been known to be a cause of male lactation, as evidenced upon the return of American POWs from the Korean and Vietnam Wars, where physical
activity and food were in short supply.
The phenomenon of male lactation occurs in some non-human species, and the lactating males may assist in the nursing.One species of fruit bat
(Dyacopterus spadiceus) is notable for this reason.
Lactation and even nursing have occasionally been observed in humans (*).
I had to edit the above a bit because all the links came in with the part I cut, but you can read the original text from the link.
I do have one question that I haven't been able to answer on Google though....
Sympathetic lactation in females.
I have heard that in a close group of female humans, that one woman can give birth and start breast feeding, and other females in the group will start
lactating. It seems like a very valid survival instinct for our species. Having more than one lactating female would increase the chances that the
young would be provided for if the primary care-giver was injured, diseased or lost.
And if this is true in humans, anyone know if this occurs in other simian groups?
(let's hear from ape and monkey folks)