Nature or Nurture?

One's sexual orientation - what is it influenced by? Is it a question of one's DNA or a question of one's environment and society he/she lives in? Personally, I think that both of the factors can influence it. On the one hand, I definitely think that sexual orientation straightly depends on the Nature. To my mind, this is something that a person "achieves" just been born. And, I am pretty sure, that it can be extremely hardly changed during the life process. However, on the other hand, I guess and can say that, all in all, one's orientation probably can be changed. This becomes possible because of the society we live in, because of our social network, our circle of communication. In my opinion, one's sexual orientation can be changed under the pressure of all these factors. All things considered, I think that both variants are possible. Though, I still prefer the Nature factor in this question.