"The study found linked DNA markers on the X (male) chromosome."

I think you'll find that the male chromosone is the Y

"Studies of male twins have suggested that about 50 per cent of the variability of sexual orientation is due to genes. This would leave about 50 per cent due to various environmental factors."

Gosh - about 50% leaves, erm, about 50%?

And, anyway, who says that male twins are a good example of human life?

Who cares whether there is a gay gene? Non-heterosexual people would be stigmatized either way. Maybe it's like being left or right handed. Any ways, I don't care whether a person is heterosexual or not. As long as they respect the fact that I'm straight and their not, they're fine with me.

I wonder, what precisely Charles Darwin would say about the existence of a gay gene. In particular, I wonder how likely he would think such a gene is to survive beyond its first generation.

The "gay gene" from the 1993 study is Xq28 and is found on the female, X chromosome, not the male Y.

As for how a gay gene would survive, please refer to http://en.wikipedia.org/wiki/Genetics_and_sexual_orientation#Correlations_with_matriarchal_lineage.2C_birth_order.2C_and_female_fertility_2