It doesn't matter what you believe. If the evidence is showing a previously unknown field around certain metal objects, you don't deny magnetics because you simply don't find the evidence to be of "quality." Even Einstein doubted some of his theories, but the math worked out. If there are countless research papers stating homosexuality is not a choice, you and I are not the arbitrator of if the data is of value and quality (well, I'm not yet, anyways). We have a stack of data, numbers that work out, correlations being established, that is how you evaluate the core premises of data. Beyond that, those qualified in the field begin to work on explanations. Science confirms homosexuality (or sexuality in general) is not a choice with the myriad of studies that confirm this hypothesis. It is from there that people try to figure out what causes it, and other forms of sexuality, and the current debate revolves around the question of how much does environment shape it and how much do genetics shape it? They have found and established genetic links, but there are some more issues that are still being worked out. And it does not matter what you believe, because what I just described is how it works, because it has been thoroughly studied and we know that is how it works.
There is no such "norm." Male or female, everyone has masculine and feminine characteristics. It's normal for men to like sports, it's normal for men to not like sports. It's normal for men to know how to work on a car, it's normal for a man to not know how to work on a car. It's normal for men to be attracted to women, it's normal for men to be attracted to men. There just is no real "norm" once you begin to look at everybody. And, of course, as a very valid question asks of us: "What is normal?"