so it looks as if er nature has kind of erm struck a bargain in this respect, that each parent can contribute exactly half, but i think it's, we're only just beginning to find out about what happens then and my guess is  about internal conflict between genes because i strongly suspect that there must be a lot of that going on because, as i think you've rightly seen, if we take this view of evolution as selecting for individual genes, then we would expect conflict even within the gender.