First of all, any scientist with a brain in his/her head knows science cannot "prove" anything. There is always evidence to support or reject a hypothesis, never "proof." You learn this in Science 101.

Second, it has not been successfully demonstrated that one is "born gay." Regardless of the current study mentioned, the consensus of researchers in this field have concluded sexuality is determined half by genetics and half by environmental influences.

In studies of monozygotic (identical) twins (who have identical DNA), researchers found sexuality was concordant (the same) only 50% of the time. If sexuality was truly based solely on genetics, then individuals with identical DNA should have identical sexuality 100% of the time. Researchers concluded sexuality is determined 50% by genes (nature) and 50% by environmental influences (nurture). This is a classic example of the nature/nurture controversy and how both affect various aspects of our lives.

That being said, yes, brains are different... But we have no way of knowing if someone is homosexual because their brain is different or if their homosexuality altered their brain structure. Sounds silly? Well, certain physical conditions (mental illnesses, for example) have been shown (again, not "proven" but shown) to actually alter the structure of the brain. Look what years of schizophrenia do to the size of the brain's ventricles, for example. And no, I'm not equating homosexuality with mental illness, I'm just providing an example about how something physical can change brain structure.

That being said, I'm bisexual. I believe part of my sexuality is due to genetics (I have a hormone imbalance) and partly due to environment (influences of friends, family, media, societal pressures, etc.).

To say sexuality, a ridiculously complicated and powerful force of our bodies, is purely genetic OR purely due to environmental influences is attempting to make this issue simplistic and black and white. Sexuality is all about a gray area, and so are the causes behind it.