MadSci Network: Genetics |
Male/female births are almost exactly 50/50. It depends on getting or not getting the Y chromosome. The Y and X chromosomes determine gender. Males are XY and females are XX -- so the father is responsible for the sex of the child since he is the only one who can pass on the Y chromosome. In terms of statistics, for all intents and purposes, it's 50/50. From what I remember, there is a slightly higher # of males born, but this evens out because slightly more boys than girl die before adulthood (due to disease, illness, accidents). As to your question about changes in the sex ratio of births after a war, I have never heard that. I think it is highly unlikely.
Try the links in the MadSci Library for more information on Genetics.