One of the most amazingly daft ideas I have ever come across is that somehow natural science can decide for us questions of morality. This is foolish, because natural science (I possess a batchelor's degree in environmental science from the University of Liverpool, so I think I know something about natural science) can only describe what is. Morality, however, is a matter of how human beings ought to behave, and that cannot be the same as how human beings do behave. Why? Because we are all agreed that there are boundaries to acceptable human behaviour. It is an unarguable fact that murder, pederasty, incest, rape and torture happen. Yet there are (thankfully) very few people who think that they are fine, good things - and quite right too!
So why is it that there are attempts to argue that we should accept homosexual behaviour because it is 'natural'? If natural science tells us that some people are disposed to homosexual behaviour, while others are not, then does it follow it's good? No! Moral questions are outside of the realm of natural science - and rightly so. Natural science tells us what is, it cannot tell us what is good.
Which is why you will not see our lawmakers going to scientists to learn ethics.