The Mutation That Saved Humanity

Surviving the Ice Age wasn’t guaranteed. Extreme cold, long winters, and scarce food

pushed early human populations to the edge of survival. Humans had fire, fur clothing,

and stone tools. But none of that was enough on its own. What changed everything

was the body. Some humans were slightly better at producing heat. They had more

brown fat, fat that burns energy to create warmth. In the cold,

those humans survived more often. Over generations, cold quietly selected for that trait.

Eventually, turning fat into heat became normal. That biological advantage made cold climates

survivable. It allowed humans to follow food north, enter new environments,