Thought you might like this! From the introduction:-
Humans only emerged from the caveman era once females realised the toughest males didn't always make the best partners. Why go for brute force when you could instead choose a clever tool-maker with better social skills? This preference for more intelligent or creative males meant testosterone levels dropped and modern humans evolved to become slimmer and more easier to live with.
theconversation.com/early-humans-had-to-become-more-feminine-before-they-could-dominate-the-planet-42952
I'm no anthropologist but it seems to make sense.