Debbie says:

One of the many good things about Nicholas Day’s article in Slate about the science of breast milk is that, pretty close to the beginning, he goes out of his way to say that “conversations about lactation always seem to require disclaimers,” and his is that lack of breast milk

has never been a death sentence. Hundreds of years before halfway-decent formula, infants were fed gruesome substitutes for breast milk (mushed bread and beer, say)—and although many more died than those who were nursed, many also survived. So the lesson of the new science of milk isn’t that formula is some sort of modern evil. (It isn’t modern or evil.) It’s that milk is really complicated—and evolutionarily amazing.

Of course, this is important because of how intensely mothers (at least white, middle-class American mothers) can blame themselves if they can’t nurse or don’t like it or don’t do it for two years or whatever the current thinking is. In my history, the story was the opposite: my mother wanted to nurse and it was thoroughly unfashionable. Her doctor wished her well but said, “I can’t help at all; I don’t know anything.” And nursing is, contrary to many people’s beliefs, often neither simple nor intuitive. So when she ran into trouble, she went to the African-American women waiting on the corner for the bus to take them (to? from?) their jobs as maids (this is Baltimore in 1951) and got their advice. I’ve always admired that–and wondered why she didn’t ask her own mother, who almost certainly nursed all three of her children.

But I digress.

In the article, Day relies mostly on the work of Katie Hinde, a Harvard assistant professor who studies breast milk in humans and rhesus macaques, and writes an occasional blog called Mammals Suck … Milk (Day shortens the name, which I think is a pity). According to Hinde, breast milk is not very well understood. L. Bode at the University of California San Diego recently published a paper demonstrating that some of the carbohydrates in breast milk are indigestible by babies … instead, they feed the bacteria in the baby’s gut, and perform a wide variety of health protection tasks in the process.

Hinde, whose field is evolutionary biology, focuses more on what she calls “milk as signal.” In rhesus macaques, “The composition of early milk seems to mold infant temperament. But—and here’s the twist—the males were much more sensitive than the females. Roughly, the more cortisol, the more bold and exploratory the male rhesus macaques were.”

Although evolutionary biology is a more sophisticated and scientifically defensible field (by far) than evolutionary psychology, nonetheless this is probably very simplistic gendering and might not withstand a more nuanced examination. There is so much data, beginning with the now almost 15-year-old Biological Exuberance, undermining binary descriptions of animal sexual/gendered behavior that I can’t trust statements like:

In rhesus macaques, daughters stay in their social groups their whole lives,” Hinde notes. “They form a bond with their mother that only ends when one of them dies. So it might be that mothers are nursing their daughters more frequently and that helps establish this bond.” In contrast, the sons end up leaving the group—and fattier milk means they nurse less often, which means they can spend more time playing with strangers, developing skills they’ll need later in life. The milk, in other words, reflects and cements the social structure of rhesus macaques.

And, of course, Day (if not Hinde) feels perfectly free to hint that these findings will illuminate human behavior.

Nonetheless, there’s more in the article about the complexity of the content of mother’s milk, and the whole thing is worth reading. I only wish that, as a culture, we were able to extend our observation of chemical/biological/hormonal/tactile substances and experiences that we know we don’t understand without trying to fit them into our extremely reductive concept of two immediately identifiable, vastly different, and non-overlapping genders.

Thanks to boingboing for the pointer, and to whatever link list got me to boingboing to find it.