the biological differences between men and women (many of which are entirely the result of estrogen, testosterone, and progesterone) do not affect one's reasoning skills or memory. however, since testosterone acts as an accelerant, perhaps men (in general) are more driven to competetive gaming?
I'm sure that socialization aspects influence the number of men and women in chess as well, but that is based upon a much larger set of variables.
(insert opinion here)
I'm probably going to regret asking this... why is there a separate division for women?