The divide between dominant and passive sex roles has long been debated, especially within the gay community.

Now, a new study suggests that there could be a genetic component to what makes a gay man a ‘top’ or ‘bottom’ in anal sex.

Researchers surveyed gay men, and found that ‘bottoms’ were more likely to be left-handed and have older brothers, while ‘tops’ were more likely to be right-handed and have younger sisters.

Researchers surveyed gay men, and found that ‘bottoms’ were more likely to be left-handed and have older brothers, while ‘tops’ were more likely to be right-handed and have younger sisters (stock image)

Stereotypically, ‘tops’ are seen as masculine, taking up the male tradition of dominance during sex, while ‘bottoms’ are seen as more feminine, taking a more passive role.

Researchers from the University of Toronto put these stereotypes to the test in the hope of understanding whether there was a biological component to sex roles.

In their study, the researchers contacted 240 men at the 2015 Toronto Pride festival, and asked them to answer a survey on their sex positions – both in practice and in preference.

The respondents were also asked about how gender-conforming they were as children – more interested in male-typical activities, and exhibiting more masculine personality characteristics.

Other questions in the survey included whether men were left or right handed, and the number and gender of siblings.

The results showed that bottoms identified as being less gender-conforming, were more likely to be left-handed and have more older brothers.

In contrast, tops identified as being more gender-conforming, and were more likely to be right-handed with younger sisters.

Speaking to Jezebel, Dr Doug VanderLaan, an author of the study, said: ‘What’s interesting about this work is even among a group of individuals who are pretty similar in terms of their sexual preference – that is, gay men preferring men – there could be a diverse set of processes that lead them to exhibit that same sexual orientation outcome.’

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In particular, the researchers say that the differences between right and left handed men are particularly useful. Hand preference is evident very early on in life, and is not usually affected by social or cultural factors

In particular, the researchers say that the differences between right and left handed men are particularly useful.

Hand preference is evident very early on in life, and is not usually affected by social or cultural factors.

But Dr VanderLaan does not think that the results should be taken at face value.

The results showed that bottoms identified as being less gender-conforming, while tops identified as being more gender-conforming

He added: ‘Sex role identity development is a complex process that unfolds over decades.

‘So the idea that some early life developmental experience that happened in the womb has a direct impact on someone’s sex role behaviour decades late seems potentially a little too simplistic and we certainly don’t have demonstrative evidence that that sort of scenario is indeed the case.’