Stop and Think About: Milk
Milk (along with toilets and opposable thumbs) is one of the main reasons I decided to start this blog. The fact that we drink milk is bizarre. Well, cow’s milk that is. We’re mammals, after all; drinking milk is part of our shtick. But to drink the milk of ANOTHER mammal? So weird.
Why do we drink milk, anyways?
First, we need to distinguish between the types of milk produced. Colostrum is produced right around the end of pregnancy, and it is loaded with all sorts of good things a newborn needs, including the antibodies of the mother. Colostrum is a great way to boost the immune system of a baby during the first few days after it is born. Not surprisingly, many humans have tried to take advantage of these properties by taking colostrum in capsule form (the benefits of these pills are disputed, however, as many of the beneficial components of colostrum should hypothetically be digested by the stomach before they can be used. One the other hand, colostrum is advertised as a great way to increase muscle mass and boost your immune system. The jury is still out on this one).
The second type of milk produced is the more common kind. It isn’t quite as nutrient-packed as colostrum, but it is still full of important vitamins and minerals, and is easily digested by babies who can’t really digest much else. Moms everywhere should be thanked for getting their children off to such a great start in life.
That’s why we drink HUMAN milk as babies, but it doesn’t explain why we drink COW milk well beyond infancy. Let’s avoid the question and talk about cows first!
Cows have been domesticated for thousands of years, and provide a valuable source of food as well as labor. They tend to be fairly non-aggressive, and have a simple diet consisting of mainly grasses (which can grow on land unsuitable for crops, thus rendering the land still usable). Cows are also adorable.
With such an easy-to-raise animal, it’s no surprise that humans started to use all of the parts of the cow they could. Meat for eating, manure for fertilizer or fuel, hides for shelter and clothing, and milk for drinking. It makes sense to me why we would have started drinking milk. If a baby was born and the mother couldn’t produce her own milk, or died for some reason and couldn’t raise her child, why not take advantage of the animals being raised all around it?
How can we even stomach this stuff?
The above idea makes sense for babies, but not necessarily adults. Adults shouldn’t even have the ability to digest milk. Levels of the enzyme that makes digestion of milk possible, lactase, starts to drop off soon after a baby is weaned. In some populations, however, lactase activity remains high. This genetic ability, known as lactase persistence, exists in three genes found in human populations (a European variety, a Middle Eastern variety, and a East African variety). There are a couple of theories out there as to why humans evolved the ability to digest milk long-term in the first place. One theory, which works best for people having the Middle Eastern/East African gene, is that this mutation was passed down because digesting milk was beneficial to people who depended on raising cattle. If you lived in one of those cultures, it was in your body’s best interest to utilize all the nutrients provided to you in the most efficient manner. The other theory, which applies to those having the European gene, is that milk is a substitute for sunlight. In other words, people living in cold climates could substitute the beneficial properties of being exposed to sunlight (such as increased calcium absorption) with the compounds found in milk (Gerbault, et al. 2009). While these theories don’t explain why humans started drinking milk as adults in the first place, it at least gives us an idea as to why we are still able to drink it today. Awesome!
I hope I’ve given you something to think about the next time you sit down to eat your cereal! Despite the fact that humans have been using the milk of other animals for thousands of years, the whole idea still strikes me as more than a little twisted. You’re drinking the fluid that comes out of another animal, produced solely for the nourishment of their babies. When it’s put that way, it makes it a little hard to ever look at a glass of milk the same way again.
What do you think about drinking cow milk? Perfectly normal, or WEIRD? Let me know in the comments.
How to Make Homemade Almond Milk (so tasty, and helpful if you are lactose intolerant like me and all other good, normal people out there)
Gerbault P, Moret C, Currat M, Sanchez-Mazas A (2009) Impact of Selection and Demography on the Diffusion of Lactase Persistence. PLoS ONE 4(7): e6369. doi:10.1371/journal.pone.0006369
What is colostrum? - LLLI
Holy Cow - PBS
History of the Cow - Straus Family Creamery