I have heard of several women who were unable to nurse their babies because of low supply. I don't know the details about how they came to that conclusion (ie. if they were correct), but I am curious how common is it for a woman to be unable to provide enough milk for her baby -- at least in the first 6 months -- I understand that after that it is normal for the baby to need some other foods in addition to breast milk.
It does not seem likely to me that a low supply could really be all that common because how would we have made it as a species if we could not feed our young a significant percentage of the time? I made this point to my sister-in-law and she countered that in many societies wet-nurses are common, so it would be possible for low-supply women to rear their young as long as a milk-producing woman was around to provide the milk.
Does anyone know? I have looked around on various websites but have not found an estimate to the incidence of TRUE low supplies.