SAME DNA DIFFERENT SEXUALITY

These identical twins share the same genes and upbringing, but one of them is straight and the other gay. They’re taking part in a new study that aims to help us understand what makes us who we are – and why we fall for who we do

With mirror-image mannerisms and matching DNA, identical twins capture something in our imaginations. They are mysterious – how many times have you asked a set of twins if they can feel each other’s pain or read one another’s thoughts? – possessing an iron-strong bond that non-twins can’t even begin to wrap their heads around. But as so much is said about twins’ ‘sameness’, what happens when they differ in one fundamental aspect of their lives: their sexuality?

New research carried out by Dr Tuesday Watts and her team of psychologists at the University of Essex seeks to determine how and why, despite having the same upbringing and the same genes, identical twins can identify with different sexual orientations. A part of this work includes looking at images of the twins throughout their lives – to see if test subjects can identify when they began to ‘diverge’ in their masculinity-femininity, with one showing signs of gender nonconformity, which is related to sexual orientation. This study found that these twins started to visibly differ from each other in this respect much later than non-twins.

So could twins actually hold the key to determining the roots of our sexuality, giving us long-searched-for answers about what really makes us who we are? The researchers believe their findings rule out the idea that sexuality is solely the product of genes, because these twins share all the same DNA. They suggest that hormones and epigenetics (the influence of environmental factors on genes) could be important.