The study basically consisted of scientists analyzing both physical arousal levels and, I think, brain activity for various subjects. They found that men describing themselves as "bisexual" nonetheless in every case showed either the same level of arousal to either men or women as men describing themselves as "gay" or "straight."

But, as the article was quick to point out, this still does not prove bisexuality does not exist, merely that perhaps as far as sexual arousal goes, in men only, there may not be any physiological evidence to show that men can be sexually attracted to both sexes equally.

Of course, I could care less whether there is evidence or not, as there is also no scientific evidence that women can enjoy anal sex as I recall, and I know women who love anal sex.