Why are males and females 50%-50%?

[cthulu2016]

25. Nicely written.

I would add, not to open a whole 'nother can of worms, that our absolutely absurd level of infant helplessness marks human intelligence as a run-away sex-slective trait. There is no way we would have come up with something as crazy as a five, six, eight year effective infancy just to make our brains so big as a method to find food or evade predators.

It has to be like antlers and swallowtail feathers and peacock tails... our brain is too gaudy and costly to have arisen through adaptive environmental factors.

And it follows that we didn't become so big-brained until we were clearly without real natural enemies. Some animals may eat people but we are no one's primary prey.