Shape of a woman’s body may play an important role in a woman’s decision to have sex because women with wider hips find childbirth less traumatic.
They have long been known as ‘child-bearing hips’. Now, a new study has revealed that women with wide hips are more likely to have one-night stands and more sexual partners in general.
The study, carried out by scientists at Leeds University, found the shape of a woman’s body may play an important role in a woman’s decision to have sex because women with wider hips do, in fact, find childbirth less traumatic.
Women with smaller hips therefore tend exhibit more cautious sexual behaviour as a result, the study suggests.
Dr Colin A Hendrie, Associate Professor of Human and Animal Ethology at Leeds University was the lead author of a study into how a woman’s build influences her sexual behaviour, published in Springer’s journal Archives of Sexual Behavior.
The researchers defined wide hips as those wider than 14.2 inches (36 centimetres) and small hips as those under 12.2 inches (31 centimetres wide).
This is measured by the distance between the upper outer edges of the iliac crest bones of the pelvis.
The 148 women in the study – aged between 18 and 26 – also had their hip circumference at the widest point measured and their waist circumference at its narrowest point.
All the women in the study had at least one sexual partner previously. They also completed a questionnaire about their sexual histories, including the age at which they lost their virginity, the number of sexual partners they’d had, and information about emotionally significant sexual relationships they had had.
The researchers found women who were more inclined to have one-night stands had wider hips.
More specifically, the women for whom one-night stands accounted for three out of every four of their sexual relationships had hips at least 0.8inches (2cm) wider than those who had fewer one-night stands.
The researchers suggest that women with wider hips have more sexual partners because the birth process is generally easier and less traumatic (than for smaller-hipped women)
Dr Hendrie said: “Women’s hip width has a direct impact on their risk of potentially fatal childbirth-related injury. It seems that when women have control over their own sexual activity this risk is reflected in their behaviour.
“Women’s sexual activity is therefore at least in part influenced by hip width.”
He explained the study findings relate back to how humans learned to walk upright and the subsequent development of narrower hips to make it easier to walk.
In the process, female hips have become just wide enough to allow childbirth. Infants are born at a less developed stage than most other primates because of this restriction, and therefore need much more care and investment after birth from their mothers and father, they say.
“We found that women with smaller hips tended to have, throughout their entire sexual histories, just a couple of sexual partners. They really only had sex with people in the context of relationships, demonstrating a more cautious sexual strategy. If they got pregnant there would be someone in their life to help them.
“Women with large hips also had a couple of relationships over that same time frame but also had a lot more one night stands. These young women would be having seven or eight one night stands over the entire time,” he said.
The team found the average age of virginity being lost was 16 and there were extremes at either end, with some women admitting to a couple of hundred sexual partners.
“The other important thing is that this study is not reflecting what men find attractive, it is about women being in charge of their own destinies, where they can control their own sexual behaviour,” Dr Hendrie said.