The point here is simply that there's a correlation between preferred sexual role and gender non-conformity. This is by no means a universal difference-there are certainly feminine tops and masculine bottoms in the world. Preferred anal sex role has been linked to gay men's degree of gender non-conformity: research has found that tops tend to score higher in masculine personality traits, whereas bottoms tend to score higher in feminine personality traits. Whereas most research in this area has treated gay men as a homogeneous group, the researchers leading this study instead looked at subgroups of gay men who differed based on their preferred anal sex role: 'tops' (the insertive partner), 'bottoms' (the receptive partner), and 'versatile' (those who are open to switching roles). This study focused specifically on exploring the potential origins of male homosexuality, but did so in a way that was very different from almost all previous studies on this topic. A fascinating new study supporting this idea was recently published in the journal PLoS ONE.
