Why the orgasm of women exists has been a topic that has puzzled science for a long time, with no apparent biological reason for that cascade of pleasure that women feel when they reach climax. A biological mystery. Now scientists believe that orgasm may have evolved in early humans to induce ovulation during sexual intercourse; a function that was lost over time in some mammals, including humans.
The same authors had published a previous work on female orgasms in 2016 in the Journal of Experimental Zoology . Their study was titled “The Evolutionary Origin of the Female Orgasm ,” in which they studied the connection between hormones and the neural reflex circuits that connected sexual intercourse with ovulation. The authors wrote at the time: “Orgasm in women obviously does not contribute to reproductive success, and surprisingly does not accompany heterosexual relationships.” In this new study they write: “The existence of the female orgasm is intriguing for two reasons: on the one hand, the female orgasm is not necessary for female reproductive success, and on the other hand, this neuroendocrine reflex is too complex to be an evolutionary accident. “.
There are multiple theories about the role of female orgasms. Some studies have found that the contractions of the uterus experienced during orgasm help transport sperm to the egg. However, many women do not reach orgasm during intercourse, and it is also common for women to conceive without climaxing.
Study with rabbits
The female orgasm could have evolved as part of a biological mechanism to induce ovulation , according to new findings published in PNAS . The study shows that female rabbits treated with antidepressants that suppress orgasms in humans release fewer eggs than normal during sex, pointing to a possible evolutionary explanation for where the phenomenon came from.
The female orgasm is not necessary for reproduction, we already know, but the complexity of the underlying neuronal and hormonal responses suggests an evolutionarily ancient origin, making researchers wonder why it is present in humans.
The researchers turned to rabbits, which exhibit what is known as copulation-induced ovulation , meaning that they release eggs when stimulated by sex, rather than cyclically ovulating as humans do. The researchers treated 12 female rabbits with a two-week course of fluoxetine (Prozac), which is known to suppress orgasms in human women. They then counted how many eggs were released after the rabbits had sex with a male rabbit, known as “Frank.”
The researchers found that rabbits treated with antidepressants released 30% fewer eggs than control rabbits . The findings suggest that the control of sex-stimulated egg release in rabbits operates through biological pathways similar to the female orgasm in humans.
The mysteries of natural selection
This supports the idea that the same hormones and brain circuits could be involved in both sex-triggered ovulation and orgasm. It could be that both events occurred in our mammalian ancestors, or perhaps brain circuits were employed at some point to trigger the release of eggs and have since become a mechanism to trigger orgasm.
However, some researchers question whether the results can be extrapolated to people. Julie Bakker, a neuroendocrinologist at the University of Liege in Belgium who studies ovulation in ferrets and was not involved in the work, told Scientific American that the study is an interesting start, but that “there is no orgasm in rabbits.”
He also notes that the effect size the team measured was small. A “30 percent reduction in the number of ovulations is very marginal. It would have been much more convincing if there was no ovulation at all” after treatment, the expert clarifies.
Referencia: Mihaela Pavlicev et al. “An experimental test of the ovulatory homolog model of female orgasm” PNAS 30 de septiembre de 2019
