It's absolutely a combination of genetic and environmental factors. If we really wanted to, we could make boys grow up more like women, and make girls grow up more like men, with regard to beliefs and behaviours. Why bother with such a thing, though? The gender gap is a lovely thing.
D'ailleurs, you could do with less clichés in your formal writing. In addition to that, possibly more important, you should never use quotations unless you're quoting something, or referring to the word rather than its meaning. "Testosterone" isn't something that somebody said, it's a hormone, it doesn't need quotes. "Average" is the same, as is "usually". In general, you should pick up the formality. Rather than "I find this funny", try "This is unusual" and the like.
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