Everyone thinks that it was the big strong caveman who got the girl, and for the most part, that may have been true, but physical strength doesn't explain how our species created civilization. I think there was always some scrawny dreamer sitting at the edge of the firelight, who had the ability to imagine dangers, to look into the future in his imagination and see possibilities, and therefore survived to pass his genes on to the next generation. When the big ape men ended up running off the cliff or getting killed while trying to beat a mastodon into submission with a stick, the dreamer was standing back thinking 'Hey, that might work, but you need to run the mastodon off the cliff.' And, then he'd mate with the women left over after the go-getters got killed.