One thing that does not yet seem to have been mentioned is that it’s unfavourable evolutionarily to have anything other than a 50⁄50 mix of males/females, as if there is a preponderance of one gender then if you are the opposite gender you’ll tend to have more babies. Of course there are exceptions to this due to things like infanticide but on the whole it’s a good approximation.
This does not explain how the first male came about of course, but it does explain how it only had to evolve once by chance and then immediately took over from there.
There are cases where artificially skewed gender balance can get corrected in a few generations:
One thing that does not yet seem to have been mentioned is that it’s unfavourable evolutionarily to have anything other than a 50⁄50 mix of males/females, as if there is a preponderance of one gender then if you are the opposite gender you’ll tend to have more babies. Of course there are exceptions to this due to things like infanticide but on the whole it’s a good approximation.
This does not explain how the first male came about of course, but it does explain how it only had to evolve once by chance and then immediately took over from there.
There are cases where artificially skewed gender balance can get corrected in a few generations:
https://www.theatlantic.com/science/archive/2016/08/the-strange-case-of-the-butterfly-and-the-male-killer/496637/