It isn't about survival. It is about procreation. If you survive to 100 years old and have no kids, you "failed to survive" in an evolutionary sense compared to a guy who died at 30 but has 3 kids.

So if the tall, muscular, lean, brave, intelligent guys can have more kids than the short, fat, hairy guys, those guys will have a greater influence on the future species than the survival in the face of catastrophy.