Social constructivism vs essentialism?

Question has been on my mind a lot because of the gay marriage bill being passed in New Zealand and just a greater awareness of the issue in general, and I was wondering what the fluther community thought of the idea that people are born with certain traits, rather than being made that way by their environment, e.g. sexuality, thirst for power, psychopathic tendencies, pleasantness, happiness, depression, generosity, a servant spirit, etc. Do you think things are more nurture than nature or vice versa? Very interested, for I sit on the fence seeing as although I’ve thought about it a great deal, I’ve only been able to sit on the fence. Opinions?