Most sexually reproducing organisms produce male and female offspring in approximately equal proportions. But this phenomenon is not just a mathematical consequence of meiosis; it is the result of a delicate balance between opposing evolutionary forces.
A 50:50 ratio of males to females maximizes the chance of transmitting any given gene on any nonsex chromosome, or autosome, to the next generation. But genes on the X or Y sex chromosomes are better off skewing the ratio in their own favor.
