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If male orgasm helps prevent prostate cancer, the purpose of the female orgasm is quite different. A new study by a Yale University researcher says the female orgasm is needed to make women ovulate.
In a new study of mammals, researchers at Yale and the Cincinnati Children’s Hospital believe that the female orgasm may have evolved as an adaptation for a direct reproductive role – the reflex that, ancestrally, induced ovulation. This reflex became superfluous for reproduction later in evolution, freeing female orgasm for secondary roles.
Since there is no apparent association between orgasm and number of offspring or successful reproduction in humans, the scientists focused on a specific physiological trait that accompanies human female orgasm – the discharge of female hormones prolactin and oxytocin – and looked for this activity in other placental mammals.
Their study, published today (Mon) in the journal JEZ-Molecular and Developmental Evolution, found that in many mammals this reflex plays a role in ovulation.
“Prior studies have tended to focus on evidence from human biology and the modification of a trait rather than its evolutionary origin,” said Gunter Wagner, from Yale’s Systems Biology Institute.
Mihaela Pavličev, from the Children’s Hospital, said: “Homologous traits in different species are often difficult to identify, as they can change substantially in the course of evolution.
The role of the clitoris
“We think the hormonal surge characterises a trait that we know as female orgasm in humans. This insight enabled us to trace the evolution of the trait across species.”
A comparative study of female genitalia also revealed that the clitoris was relocated from its ancestral position inside the copulatory canal – an anatomical change which made it less likely that it receives adequate stimulation during intercourse to lead to orgasm.
Women hoping their partners will have no excuses after reading the paper may be left disappointed, however.
While the scientists have traced its evolution, they admit the human female orgasm’s “novel characteristics” that distinguish it from other mammals still leaves some questions left unanswered.
Agencies/Canadajournal
