Discuss. (for you Bryan Ekers 
)
Note: I like to read others opinions first and then reply
I think you gotta define “tomboys” a little more specifically.
Girls who behave in stereotypical masculine ways and have stereotypical masculine interests.
I would say that “tomboyness” is determined in the same way that most other personality traits are - a random mix of nature and nurture, probably in roughly equal doses. Just a WAG guess stemming from common sense, of course.
Jeff
Well, if you’re talking about female-to-male transsexuals, studies have been done showing that prenatal exposure to hormones efects the hypothalamus to create a “male brain.”
If you’re just talking about girls who like to play sports, I dunno . . .
Eve, I understood it to be the latter. Though thanks for the transsexual info.
I’m talking about any end of the tomboy spectrum
Its probably a little bit of both in my opinion, but I’m a very indecisive person, so whatever. I mean everybody is born with a personality of their own for sure, cuz me and my brothers all acted differently when we were infants, or so my mom says. But part of personality also comes from experience. Lets say theirs a girl with two older brothers and they get lots of recognition from their father for playing sports, it could be a trigger in a younger girls mind that if she played sports her father would be more proud of her. Thats just an example, I’m not saying all “tomboys” become “tomboys” for that reason. I dunno, thats the best theory I can come up with for now.
Well, I think “tomboy” still needs to be defined. I’m not being nitpicky, but depending on one’s own experience, “tomboy” can mean a bunch of things that may or may not be related. Depending on your social class, geographical location, and existence in time, “tomboy” can mean anything.
For instance, I considered myself a tomboy growing up. I didn’t like wearing dresses or playing with Barbies or getting my hair prettified. I wanted to be a cartoonist, an astronaut, and a scientist when I grew up. I also loved getting dirty. Masculine traits, right? However, I liked playing house and pretending that various pets and dolls were my children. I’ve never desired sports activity in my whole life and I never wanted to be physically strong or particularly rough-and-tumble. So was/am I am tomboy? Or was I just an individual with a diverse set of interests?
On a basic level, I think you can be born with a brain hardwired for “masculinity” or “feminimity”. Neuroscience has fleshed this idea out with solid data, and from an evolutionary perspective, it makes total sense. But as has been said before, the labeling of personalities as “masculine” and “feminine” is very sensitive to the nuturing environment. I don’t think a preference for sports or easy-bake ovens is linked to sex chromosomes or activated by testosterone or estrogen.
I think some girls who are tomboys have “male-like” brains, but on the spectrum of tomboyishness, these children are at the extreme and are a small minority. Most tomboys (and “sissies”) are probably like myself: we simply bear personalities that aren’t conducive for traditional gender labeling.
I noticed that many tomboys I knew were the only girls among a family of boys. One of my cousins, for example, had only her older brother, and her mother died when she was only three or four. She used to lean towards boy toys (trucks, action figures) when she was young-although she did love Barbie dolls.
YMMV
I was a tomboy when I was little, then about the age of 12 I baceme more “ladylike”. Now I can go either way. And no, I wasn’t in a family of all boys. My dad just raised me on hunting, the outdoors, and respecting the world we live in.
My vote is for nature, with a smattering of nurture. I don’t have any sisters, so I grew up doing all sorts of “masculine” stuff with my brothers – hiking, playing sports, etc. For that matter, I’m still a mean shot with a snowball. To my mother’s dismay, I never had any desire to play with dolls, and the only dolls I liked were a set which showed the different ways people around the world dressed. I don’t remember playing with dolls, and I’m still not into stuffed animals.
On the other hand, my neice is also an only daughter, and she loves Barbies and other dolls. I’m afraid I still don’t get the doll thing, so I wind up getting her crafts and games which she also enjoys.
Like I said, I just don’t understand playing with dolls. Chemistry sets, on the other hand . . . 
CJ
Explosion? What explosion?
This gets into the gender vs sex thing, right? I, IMHO, would say that in some ways “girls” and “boys” are the roles that are “made”. Yeah, there ARE natural differences and tendencies but I think often the society demands a much more overt display of gender than some people feel natural with. I was a tomboy, but it was never a choice for being male but rather a choice against acting female, which just took too much effort and reduced your options for having fun-- I think I was just acting in a natural kid way (playing, getting dirty, curious, etc-- wearing white dresses is counterproductive to fun). I think a “proper” feminine gendering takes a lot more learning in childhood than male gendering, although both are learned behaviors-- if a kid doesn’t jump at either and remains in the middle without develping these roles they appear 'tomboyish" (if a girl) or “nancy-boy” (if a boy). Ugh. “When women act like women, they are accused of being inferior. When women act like human beings, they are accused of behaving like men” (Simone de Beauvoir).
I made a few tomboys back in ym college days.
Damn, that was fun.