According to a study published in the Journal of Experimental Zoology, the female orgasm was developed by mammals about 150 million years ago.

The reason is that it accumulates a series of bodily actions which would allow the female to release eggs so they are fertilized after sex. It is the first time a study proves to be satisfactory when it comes to explaining the origin of the elusive female orgasm, as most biological features have a determined purpose when it comes to surviving and reproduction.

Scientists have been puzzled by the fact that unlike male orgasms, the female orgasm is not necessary for achieving reproduction. Image Credit: Mushene

The study carried out by Mihaela Pavličev from the Department of Theoretical Biology at the University of Vienna, points out that the factor keeping scientists in doubt is that the female orgasm does not appear to contribute to the reproductive success, as it is unreliable on regular intercourse. At first, the scientific community believed that there had to be a reason for the female orgasm to persist throughout time. One of the theories suggested that it simply was a counterpart to the male orgasm, but in contrast, the male orgasm is indeed vital for achieving reproduction.

An orgasm is characterized by rhythmic muscular contractions in the pelvis conjoined with sexual pleasure. It is a process controlled by the autonomous nervous system, causing euphoria and relaxation after it has occurred. On women, the orgasm has been associated with the process of induced ovulation, which led researchers to believe that it served as a mechanism to induce ovulation and thus achieve reproduction more easily.

Scientists had to believe that the female orgasm has an ancestral origin, mainly because its appearance during heterosexual intercourse is very uncommon. Female mammals have been proven to have more orgasms through masturbation or by having homosexual intercourse, and there also is no correlation between the number of children that a woman has and her orgasms.

The study shows that most female mammals, including humans, share the same hormonal release when they orgasm, which suggests that there must be some clear relationship between the reproductive functions that are linked to a female’s capacity to reach orgasm.

The key: Ovarian cycles

One of the traits that female mammals share is that they undergo very precise ovarian cycles. Mammals’ reproductive behavior dictates that they must perceive internal fertilization, which also depends on the maturation of the egg and the sperm successfully reaching the egg.

Depending on the time of the year, external temperature or the availability of a partner, female mammals are able to reproduce. Species that are able to spontaneously ovulate are typically affected by the environment, as their reproductive cycle depends on the season. This includes all mammals indigenous to North America, Europe, Africa and Asia, which are included in the Eutheria clad.

Although there is not much information regarding the origin of the different types of ovulation in mammals, the authors managed to differentiate three types of ovulatory cycles: spontaneous, male-induced, and externally-induced.

Using these classifications, different species of mammals were set in a chart to see their relationship when comparing their ovulation process and the location of the female’s clitoris, the main organ responsible for triggering the female orgasm.

The researchers determined that male-induced ovulation can be classified as ancestral, while spontaneous ovulation is closely related to regular cycles of ovule production, which has changed on each mammal species throughout evolution.

After establishing links between the ovarian cycles and the anatomy of several mammals whose females are known to experience orgasms, the team proceeded to try and understand the hormones related to the stimulation of the clitoris and the event of orgasm itself. Regardless of genre, humans and mice appeared to secrete the same hormones when reaching orgasm.

The hormones behind the female orgasm

One of the hormones that were linked to orgasms is prolactin (PRL), and it is also present in both environmentally-induced ovulation and male-induced. Previous research shows that PRL is responsible for causing arousal in lemurs and mice, while also having an effect on embryo development. Intercourse causes the body to excrete PRL, alongside other hormones. Researchers believe that stimulation of the clitoris is what causes the hormone to appear, which acts upon estrogen receptors and promotes progesterone reception.

This process was found out to vary slightly between species, but in essence, it was the same for most of the surveyed mammals, especially rodents. It seems that PRL has a wide range of important functions in the reproductive cycle in both sexes, which predates most of the current species of mammals, including humans.

The same hormones that are released alongside PRL make it so the egg is more easily fertilized, thus ensuring procreation. The determining factor was that primates developed social behavior, which in part assured them a potential mate. Females were then able to choose their mates as they pleased and the female orgasm appeared to have lost its reproductive purpose.

Because seasonal ovulation predominated the reproductive cycles of primates, the female orgasm remained as an ancestral method of transmitting a signal to the brain to ensure reproduction, which closely relates to the purpose of the male orgasm. The difference is that males’ orgasm triggers ejaculation, which is vital to fertilize the egg amid the reproductive act. Whether the female reaches orgasm or not had lost its significance throughout the ages, and now, thanks to this research, the female orgasm is one step closer to being fully understood.

Source: Journal of Experimental Zoology