That's not how evolution works.You can't pass on PTSD. If grug is born brave, but then has half his hunting party devoured by a cave lions and gets PTSD, his sons DON&quot;T get PTSD, they're likely to inherit his original foolhardyness, because that is a genetic component while the cave lion encounter is not. If Grug was born a coward, and ran the moment he heard the cave lion while his companions tried to fight it off, then he's likely to pass on his cowardliness to his sons, irrespective of the fact that the lion kinda validated him. Evolution does not care in the slightest what you do in your life, just that you pass your genes. 