Why would evolution keep genetic variants that can make us seriously ill?

Added: 2026-06-02

[00:00:00]Let me start with a paradox. Why would evolution keep genetic variants that can make us seriously ill? You often think evolution optimizes for health, but it doesn't. It optimizes for survival in a specific environment. And sometimes what helped us to survive in the past make us really ill today. We encountered a striking example of this during the COVID pandemic. At that time, researchers worldwide were asking a simple question. Why do some people develop severe disease while others don't?

[00:00:35]One of the strongest genetic signals pointed to a variant called RS1138 593242.

[00:00:42]This variant sits in the region regulating the gene LZTFL1 and it carries an unexpected origin. It comes from Neanderthals. So, COVID didn't just reveal a disease mechanism, it revealed a piece of our evolutionary history still active today.