Sexuality research studies gay and straight twins

Sarah, right, and Rosie, left, were at the centre of a study by scientists trying to work out the root of human sexuality. Photo / Facebook

Scientists searching for the root of human sexuality studied identical twins, one of them straight and the other a lesbian, who grew up in the same environment.

Sarah Nunn and Rosie Ablewhite, 29, present a mystery for researchers looking to identify genetic and environmental interactions that form sexuality because Sarah is attracted to men while Rosie is attracted to women.

The origins of their differing sexual identities were studied in an effort to find out when and how sexuality develops in childhood.

The identical twins were brought up in the same household, ruling out parenting and genetics as the causes of their difference. Photo / Facebook

Sarah remembers how Rosie's tomboy tendencies provided an insight when they were growing up, telling

The Times

her boyfriends "instantly felt more at home" with her sister.

"She liked football, talked about boy things, played video games," she said.

'They'd be like, "Sarah, you're really boring. I'm going to go and play with Rosie."

"I'd get jealous that they liked her better."

But Sarah soon realised that her sister just wasn't as interested as her in the company of boys.

'When they tried to get romantic with Rosie she'd say, "That's not me." Then they came back,' she explained.

Now they and 55 other twin pairs are at the centre of a study by University of Essex researchers.

In the past, scientists have searched for signs of how sexuality manifests before puberty, such as gender-atypical mannerisms of behaviour.

Scientists are studying genetically identical twins who diverge in sexuality in order to establish what causes sexual preferences. Photo / Facebook

But it is difficult to determine whether reported behaviourial patterns have been remembered accurately.

Gerulf Rieger and his colleague Tuesday Watts circumvented this problem by using photographs in their study for the journal.

They asked Sarah, Rosie and other twins with 'discordant sexual orientations' to send them childhood snaps, before showing them to people who did not know the purpose of their experiment.

The idea was to see if people could spot how and when the twins diverged just from looking at their clothing and play.

Their questions are controversial, as establishing links between sexuality and other aspects of gender could be seen as reinforcing stereotypes about male and female behaviour some believe are harmful.

But these stereotypes are difficult to avoid in the pictures submitted by Sarah and Rosie.
As toddlers, Sarah is seen wearing a dress and playing with a Barbie, whereas Rosie dons a Batman suit and plays with Aladdin.

Later in childhood, Sarah dresses up as The Flintstones character Wilma, but Rosie opts for Fred. Throughout her early years Rosie's favoured attire is dungarees.

And 20 years on the twins are puzzled as to how it took so long to realise they were different.

It seemed impossible to them that they could diverge on something so fundamental while being identical twins.

Rosie remembers questioning why she didn't feel the same passion for boys as her sister.

Childhood pictures of Sarah and Rosie along with submissions from other twin sets offer an insight as to how differences in sexuality develop. Photo / Facebook

"I questioned it for so long,' she said. 'Sarah was really boy crazy."

When Rosie had a boyfriend she realised she didn't want to kiss him, so Sarah stepped in.

"I said to him, "I'm the same . . . I will kiss you"," Sarah recalled.

Researchers found that the differences Sarah and Rosie experienced at an early age were discernible in other twins" photographs too.

From about the age of six in girls and eight in boys, there was a marked divergence in the way people rated the photographs.

Dr Rieger said the sexuality differences asserting themselves years before puberty gave useful information about the development of sexual identity.

"What we can do is rule out a few things now," he said. "A lot of people jump to the conclusion it must be genetics."

Scientists have established a genetic component to sexuality, but they have also claimed that is not the whole story.

And given this study's twins share the same genetics, that component can't be the whole story in these cases, with Dr Rieger looking to environmental factors.

"This shows there is something early on, in the early environment, that has nothing to do with genes but can still have a tremendous effect on sexual orientation," he said.

The research also ruled out parenting as far as is possible to do so, because all the twins studied shared the same home.

Dr Rieger believes the most likely explanation for the divergence is something that happens before birth.

"Prenatal hormones are the number one candidate," he said. "Our theory is that even though twins are identical, what happens in the womb can be quite different.

"They can have different nutrition, different levels of hormones."

Photographs were shown to people ignorant of the study's purpose, in order to see if they spotted differences in clothing and play. Photo / Facebook

Dr Rieger says he won't be have research into stereotypically gendered behaviour hampered by the controversy people attach to it.

"To me it's just one way of assessing behaviours — that is a better method than asking people," he said.

"It doesn't matter to me if it's controversial. It's very dangerous to start going down the route of thinking that way."

Another 30-year-old pair, who wished to remain anonymous, hope their involvement in the study helps answer questions they have asked for years.

"I was always fascinated with it," one of the twins said. "My mum and dad were fascinated.

"How can it be that one egg split and in such a large factor of our life we were programmed so different?"

Like Rosie and Sarah, the sisters found their interests diverged early in childhood.

"We were so alike in some ways but also so different. I was a bit of a tomboy," said the gay twin.

"I would play in the garden. She was very into make-up."

Their music interests also clashed, with one preferring Jimi Hendrix while her sister listened to boy bands.

Twins have long been used by scientists trying to estimate the effect of genetics and environment.

Because twins can be identical, sharing all their genes, or non-identical, which means they share just half, scientists can determine the contributions of nature and nurture.

Identical twins are more likely to have the same sexual preferences than non-identical twins.