OK, so this is in mice, but if lab mice are engineered to not have the TRPC2 gene, or if they remove the pheremone receptor in their noses, females start acting like males and shag around, become riotous and leave their kids after as little as two days if a male comes around.
The most interesting inference the scientists made is that basically male / female behaviour is not hardwired into the brain, but comes (for a large part, and at least in mice) from this gene. Thus, there is only one basic model of brain for each species. The body around it creates the gender differences.

edit: 7/8/7
Of course, this study that show that women over 65 who have drunk more than 3 cups of coffee per day have better memories than those who didn’t (and for men it doesn’t make any difference) puts a bit of a cloud on that idea, hey?