Well, it's not too difficult to find accounts of the latest research into sexual orientation on the internet. Twin studies are always interesting: I could explain why, in terms of DNA, environmental factors and so on, but that information is readily available. Briefly, by comparing identical twins with non-identical, and also comparing twins who have been separated and adopted into different families, it is possible to get some useful information about the interplay of genetics and environment.
The results from a number of recent twin studies in America, Australia, Sweden and other places suggest that genetic make-up has a significant, though not completely determining effect on sexual orientation. Other factors can include the hormones present in the womb (reception of which can differ in two identical twins in the womb). There is also evidence of differences in brain structure between heterosexual and homosexual people. So our DNA does not completely predetermine our sexual orientation, but has a strong influence on it, and other physiological factors are also highly influential, but not wholly deterministic.
Science does not answer the question, nor does it take away our freedom. I believe it would be as unnatural for my gay friends to try to be straight as for me to try to be gay. There are real questions here; questions of how we read the Bible, including difficult verses such as Leviticus 19:19 and Leviticus 19:27, or Deuteronomy 23:1 - I trust that those who quote scriptures about homosexuality are equally rigorous in sticking to those verses.
There is also the question about the love we show each other on these boards – how truly are we serving God by ridiculing each other's positions (e.g. by suggesting that liberals are in favour of paedophilia or inappropriate behavior with animals) rather than responding calmly and rationally?
Sorry for the long, dull post. God bless you all.