Originally Posted by ACt
Well, Numinous, I may argue that since all development begins normally and only when the Y chromosome kicks in does "maleness" developed and that if, for whatever reason, the Y chromosome fails to activate or is not present (the XO genotype) the phenotype is female, that the default (in humans) is female, so we all begin to develop as a female does.
Of course, that's being very broad and your point of the early stages of development are, for the most part, sexless, is well taken.
I just prefer to determine male and female after the second sexual gene commences to be expressed (or not). That's why I don't consider the XO genotype as an indicator of what is the default gender, because said genotype only manifests after the (lack of) second gene is expressed.
It's just a convention I learned in college, other countries might have other conventions.
Also, it'd be interesting to see what HR has to say about the XXX, XXY and XYY genotypes.