Nine out of every 10 glasses of raw milk produced in the world come from domestic cattle. The remaining one is sourced primarily from goats, buffaloes, sheep, and camels. Less commonly, humans consume the milk of a menagerie of domesticated and semi-domesticated ungulates, such as alpaca, elk, llama, moose, musk ox, and yak.

Altogether, global dairy operations produce some 700 million tons of milk each year. But there is, of course, one more species missing from this list of milk providers: our own.

According to the CDC, more than three-quarters of American parents provided at least some breast milk to their infants in 2013. While there are many benefits to breastfeeding, one of its primary functions is to provide nutrition to a growing infant. But what’s actually in human milk, from a nutritional perspective? How similar is human milk to milk produced by domestic cows? And what other animals might have milk closer in make-up to our own? Fortunately, the scientific literature is awash in milk research.