In the course of discussing milk, it's prudent to bring up the fact that there is a fair percentage of the world's population who cannot drink milk without a certain amount of physical discomfort. This condition, brought on by the lack of the enzyme lactase in a person's biological make-up, is called Lactose Intolerance.

Lactase helps a person metabolize lactose into galactose and glucose, both of which are types of sugar. These sugars are easily broken down in the small intestine. If there is no or limited lactase available to break down the lactose, the milk molecule will ferment and release carbon dioxide. I'll let you figure out what happens next.

A typical human is born with the ability to create a fair amount of lactase. This makes sense when realizing that mothers breast feed their children after their birth. As a child is weaned off of mother’s milk, the need for lactase decreases. As a person grows older, they produce less lactase, making digesting lactose more difficult and thereby making drinking milk a less desirable proposition. However for some people on this planet, this is not an issue as they have lactase persistence.

What makes Lactase Persistence so interesting to me is that it's a dietary genetic mutation that has occurred in homo sapiens that has created a clear delineation within the world population. Sometime between 4500 and 4000 BCE, a group or groups of people adapted to their diet of milk, even after weaning off of mother’s milk. This adaptation allowed their bodies to process lactose long into adulthood. If you can drink milk without difficulty, it's reasonably safe to assume you can trace your ancestry to Western Eurasia and/or parts of the Mediterranean. If you can't drink milk as an adult, some of your ancestors come from elsewhere in the world.

The fact that's often lost upon most of us Western Eurasian Descendants is that Lactose Intolerance is the de facto baseline of homo sapiens. It's us adult milk drinkers who are the anomaly amongst the world population.

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