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.
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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.
This budget will allow us to conduct an experiment with 10 females in the control group and 10 in the treatment group and two males for breeding. Animal husbandry costs are calculated on the fee basis at Cincinnati Children's Hospital Medical Center for 22 animals over a two months period of housing. Oxytocin will be monitored to control whether copulation was successful. With more funding we will be able to reproduce this experiment with ferrets, another species with copulation induced ovulation. A second experiment with ferret would greatly strengthen the study.
1. we will breed 10 females with the two males without intervention to first estimate the baseline pregnancy rate with the animals we have.
2. The experiment will include 4 weeks treatment with Fluoxetine prior to breeding.
3. Breeding and assessment of breeding success will be performed over a 4 week period with one control and one treatment female per trial and switching males between treatment groups at each pair of breedings.
4. Blood samples will be collected for hormone screen.
Aug 27, 2017
Nov 30, 2017
breeding rate estimates (item 1 above) will be available after six weeks.
Jan 31, 2018
the actual experiment will take another two month
Feb 28, 2018
Data analysis and interpretation
Apr 30, 2018
manuscript prepared for publication
Meet the Team
I am an evolutionary biologist interested in the evolution and origin of complex traits. Most recently my lab works on the evolution of mammalian pregnancy and the origin of novel cell types, and issues of women's health.
I am evolutionary biologist interested in how developmental structure affects the way the evolution changes traits, and results in a diversity that we see across species. In the recent years, my research has focused on explaining the evolutionary history of human female sexual traits- mostly reproductive traits involved in pregnancy, but not limited to these, such as menstruation and female orgasm. Understanding the evolutionary history of these traits will help us understand their developmental basis, as well as how they function, and why they sometimes malfunction the way they do.
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