Do you know anyone who is lactose intolerant? Chances are, you probably do! That’s because most people are at least slightly lactose intolerant, or may become so with age. But what exactly is lactose intolerance, and why does it seem to affect everyone differently? To find the answer, we can take a look into our genetic makeup and evolutionary history. But first, lets learn a little more about what lactose is and how it interacts with out body.