Why are males and females 50%-50%?

[cthulu2016]

12. Fair enough

I should not have said conception. Particularly since all fetuses are developmentally female and must make a tricky change to become male, which results in a high failure rate. (And accounts for the greater variability in males born, also. Higher defect rate, etc.)

But by noting that discrepency in what I said your are arguing my case (which isn't my case, of course, it's everyone's case).

The huge spontaneous abortion rates of male mini-fetuses mandates an over-production to acheive rough parity in actual, practical reproductive terms.

Either way, our species (and a lot of others) will graviate toward a practical 50-50 for very good reasons.