Man or Woman?

[Gil Hamilton]

Probably a combination of steroids and human growth hormones. The growth hormones cause parts of the skull to continue growing, which is why Barry Bonds has gained two helmet sizes since he started taking steroids and HGH (which, of course, he denies taking). The steroids cause the female to take on more male characteristics, such as pattern baldness and deepened voices.

This is certainly the case. Male and female morphology has alot to do with relative testosterone levels. You pump a woman full of testosterone (and she'd have to be, no human being gets muscles like that without being flooded to hell and back with testosterone), she'll take on male characteristics, including significant growth of body/facial hair, loss of significant mammaries, et cetera. It works in reverse for men. Pump a man full of estrogen for long enough and his body will grow fully functional breasts, which can lactate and everything.

An example of how closely tied sex is tied to hormones, there is a genetic disorder in places where a developing embyro will have an XY chromosome set, but due to a genetic quirk, won't produce the normal testosterone surge that comes mid-gestation to make male genitalia and the baby will turn out morphologically female. That is, until the child hits puberty, at which point he'll get the normal supercharge of testosterone and he'll go from "female" to a fully function male, same as any man. These individuals are fertile and everything, utterly normal biologically. The article I read this from says this happens in this one region of the Dominican Republic most commonly and what's cool is that the individuals are completely one hundred percent psychological normal as well (Hispanic culture helps, having your little girl turning out to be a boy after all is not really seen as a bad thing).

Gender is partially genetics, but when it comes down to it, alot of what sex you are comes down to hormones and social convention.

[Rye]

True that. There's even examples in nature where the system is totally flip-flopped and the females are more aggressive and have strongular musculature and bones, and even larger penises than the males; hyenas are the only ones that spring to mind, but there might be more.

Hyena females are considerably larger than the males. The females are masculinized due to the excess testosterone in their bodies; they have more testosterone in their bodies than most male hyenas. As a result of this masculinization, females are a third larger than the males, have more muscle mass, are more aggressive, and have masculinized genetalia.

The erect 'penis' of both sexes plays a prominent role in ritualized greeting.

The "false penis", which is actually a fusion of the clitoris and labia of the vagina, seems to be used in dominance displays and to indicate aggression and willingness to fight. Female hyenas dominate over males in many cases, and they behave in the way that male wolves do when establishing pack heirarchy: they often "mount" subordinate animals, and an "erection" indicates they are confident of being able to take on a challenger in a fight.

Their rather unique genitalia, and the accompanying high levels of "male" hormones, is probably very much connected to their social order and dominance structure. As with wolves, usually only the dominant one or two hyenas in a pack breed in a year. Levels of testosterone are connected to dominance and aggression; and it is likely that the most "male-like" of the females were traditionally the ones that fought their way to the top of the pack, and thus bred. Over the generations this would have selected females closer and closer to the male model, until they became more "male" than the males.

This said, it is not without cost. The first pups a hyena female has have to rip the psuedo-penis open in order to be born; these pups are almost invariably suffocated during the process, and it is not unknown for the hyena mother herself to sustain too much trauma and die of it.

http://www.answerbag.com/q_view.php/3185

[Inquisitor Ryan]

This said, it is not without cost. The first pups a hyena female has have to rip the psuedo-penis open in order to be born; these pups are almost invariably suffocated during the process, and it is not unknown for the hyena mother herself to sustain too much trauma and die of it.

OUCH!!!! This is why i'm happy to leave the childbearing to the women.