Why Are So Many People Lactose Intolerant?

Humans are the only mammals who eat dairy into adulthood.

Photo by Mae Mu on Unsplash

When I was a junior in college, I thought I’d developed an ulcer. I would get gnawing gut pains, sometimes accompanied by burping or bloating. I looked up the symptoms in a textbook (there was no internet in those days), and all signs pointed to acid reflux. It made sense, what with all the…