Why do almost all species birth 50/50 males/females?

Take a thought experiment, where there's a species with a sex ratio of 10/90 for some reason – maybe some researchers edited the genes – that is, 10% of the time a sperm meets an egg, the result is male, and 90% of the time, the result is female.

Will it stay on 10/90 in the long run?

Well, what happens for an individual who makes a bit more males than females? That individual's genes will be more successful. It's the same old story. The only stable state is 50/50, which is where the ratio ends up after some number of generations. But why 50/50, not, say, 60% males 40% females?

I want examples. I think some species make a skewed adult sex ratio by eating some of their young? Or?

What links here

• Evolution