Study plots orgasmic origins
Why do women orgasm?
While many are more concerned with the ‘how’ than the ‘why’, the purpose of the female orgasm has puzzled biologists, anthropologists, and philosophers for centuries.
Male orgasm has a clear reproductive function, as it is coupled to sperm transfer, and it now appears that the female orgasm may play a role in reproduction too.
A new study presents evidence that the human female orgasm is derived from a reflex that in many other mammals is necessary for ovulation.
It suggests that female orgasm originally had a reproductive function but lost it when spontaneous ovulation evolved, a situation found now in most primates including humans.
At almost the same point in our evolutionary history, the anatomy of the human female’s external genitalia changed so that the clitoris was removed from the copulatory canal.
This may help explain why many women do not have orgasm during intercourse but are able to reach orgasm during masturbation or through clitoral stimulation during intercourse.
It was a hard thing to work out, because an orgasm is not always an orgasm.
“Homologous traits in different species are often difficult to identify, as they can change substantially in the course of evolution,” said lead researcher Professor Mihaela Pavlicev.
“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.”
The authors concluded that female orgasm did not evolve in the human lineage, but millions of years before.
They say that it may now have acquired additional roles after it was no longer used for ovulation.
“The hypothesis that female orgasm may have evolved as an adaptation for a direct reproductive role, and the fact that it is not necessary in humans to conceive, are not contradictory at all,” the report said.
“We suggest that the ancestral trait that evolved into human female orgasm had an ancestral function in inducing ovulation.
They suggest that what is now the female orgasm used to be “the neuroendocrine reflex [a hormonal surge or orgasm] present in species in which ovulation is dependent on physical stimulation during copulation, such as rabbits or cats.”
The evolutionary disconnect of copulation from clitoral stimulation, which coincides with anatomical changes in the primate lineage, is only possible when the ovarian cycle becomes autonomous. This meant that afterwards, the clitoris could be coopted into new, primate- or human-specific roles.