About This Project

Human females ovluate on a monthly cycle. Rabbits and many other mammals are physically induced ovulators. This means that rabbits ovulate due to a stimulus from mating. Last year we proposed that female orgasm in humans evolved from physically induced ovulation. We hypothesize that using drugs that inhibit orgasm in humans will reduce ovulation in rabbits compared to untreated females. The results of this study may have profound implications for the understanding of female sexuality.

Ask the Scientists

What is the context of this research?

Male orgasms have a specific biological function, sperm transfer. The female orgasm has no known specific biological function. We want to test our hypothesis about the ancestral roots of the female orgasm. We hypothesize that the female orgasm is a vestigial trait carried over from the time when ovulation was induced by copulation in our ancestors. We can’t test this on humans because humans ovulate cyclically. However, rabbits are still physically induced ovulators and we want to test whether female orgasm and rabbit ovulation have the same physiological basis. We plan to test our hypothesis by using drugs that, in humans, lead to the inability to have orgasm (anorgasmia). We predict that these drugs should prevent copulation induced ovulation in rabbits.

What is the significance of this project?

In the 20th century, Freud theorized that the fact that some women never experience orgasm during heterosexual intercourse was explained by the women being psychologically immature, an explanation with devastating effects on the woman's life. Other theories say that a man who cannot give an orgasm to his partner is sexually deficient. In contrast, our hypothesis suggests that neither of those theories is true. If our results show that female rabbits have lower ovulation rates if treated with drugs that inhibit orgasm in humans we will have data supporting our hypothesis that the female orgasm and copulation induced ovulation are evolutionarily related. Regardless of how the results turn out, we think that it is really important to know whether our model is supported.

What are the goals of the project?

We want to directly test our hypothesis by examining whether copulation induced ovulation and female orgasm share the same physiological basis. We know that antidepressant drugs of SSRI type lead to the inability to have orgasms in humans (Balon 2006 Am J Psychiatry 163, 1504). If female orgasm evolved from coulation induced ovulation, SSRI drugs should also prevent ovulation in animals with copulation induced ovulation. To test this we will feed female rabbits an antidepressant drug and breed them to monitor the number of eggs produced after copulation. If treated rabbits have a lower ovulation rate compared to untreated female rabbits, the data will support our hypothesis that human female orgasm evolved from copulation induced ovulation.