Researchers reveal an evolutionary basis for the female orgasm

Following hormonal biomarkers across a wide variety of species helped scientists piece it together.

 

Two women kissing, love, sex, lesbian.
Photo by Roman Khripkov on Unsplash

Few things are as magical as the female orgasm, whether you are experiencing it, inducing it, or just a casual observer. It is essentially pure art in motion. Yet, there are many things we don't know about the phenomenon, scientifically speaking, such as, why it exists. Scientists have been pondering this for centuries.


Apart from vestigial organs, there are few structures in the body we don't know the function of. It seems that the clitoris is there merely for pleasure. But would evolution invest so much in such a fanciful aim? Over the years, dozens of theories have been posited and hotly debated.

One prevailing theory is the “byproduct hypothesis." The penis gives pleasure in order to drive males toward intercourse and ensure the perpetuation of the species. The sex organs are one of the last things developed in utero. Due to this, and the fact that women develop their pleasure organ from the same physical structure the penis is formed from, the clitoris is therefore a “byproduct" of the penis. You could imagine how some women feel about this theory.

Another is the mate-choice hypothesis. Here, it is thought that since a woman take longer to “get there," it would pay for her to find a mate invested in her pleasure. A considerate lover would make a good father, the theory posits. Yet, the female orgasm happens rarely during penetrative intercourse, undercutting this theory.

It's been thought that the act plays a role in conception. Several studies have shown that the woman having an orgasm during intercourse increases the likelihood of impregnation. But how and why is not well understood. Now, a team of scientists suggest that the female climax once played a role in reproduction, by triggering ovulation.

Mary Magdalen in Ecstasy. By: Michelangelo Merisi da Caravaggio. 1606.

Researchers at Yale University posed this theory, in a study published in the Journal of Experimental Zoology Part B Molecular and Developmental Evolution. Gunter Wagner was its co-author. He is a professor of ecology and evolutionary biology at the university. According to him, previous research has been looking in the wrong place. It focused on how human biology itself changed over time.

Instead, these Yale researchers began by analyzing a large swath of species and the mechanisms present in females associated with reproduction. Wagner and colleagues also looked at the genitalia of placental mammals. They focused on two hormones released during penetrative intercourse across species, prolactin and oxytocin.

Prolactin is responsible for the processes surrounding breast-milk and breast feeding, while oxytocin is the “calm and cuddle" hormone. It helps us to bond and feel closer to others. Placental mammals in the wild need these two hormones to trigger ovulation. Without them, the process cannot occur.

One major insight researchers found is that in other species, mammalian ovulation is induced by contact with males, whereas in humans and other primates, it is an automatic process operating outside of sexual activity, called spontaneous ovulation. From here, they looked at those female mammals who induce ovulation through sexual contact with males. In those species, the clitoris is located inside the vagina.

The process of human ovulation. By MartaFF [CC BY-SA 4.0], via Wikimedia Commons.

Evolutionary biologists believe that spontaneous ovulation first occurred, in the common ancestor of primates and rodents, around 75 million years ago. From here, Wagner and colleagues deduced that the female orgasm must have been an important part of reproduction in early humans. Before spontaneous ovulation, the human clitoris may have been placed inside the vagina. Stimulation of the clitoris during intercourse would trigger the release of prolactin and oxytocin, which would in turn, induce ovulation. This process became obsolete once spontaneous ovulation made it onto the scene.

“It is important to stress that it didn't look like the human female orgasm looks like now," said Mihaela Pavličev, Wagner's co-author of this study. "Homologous traits in different species are often difficult to identify, as they can change substantially in the course of evolution." She added, “We think the hormonal surge characterizes a trait that we know as female orgasm in humans. This insight enabled us to trace the evolution of the trait across species."

While the hypothesis is compelling, it has drawbacks. The biggest is that it's difficult, if not impossible, at least currently, to investigate what, if any, sexual pleasure other female animals derive during copulation. Other experts say, more data is needed from other organisms to shore up this theory. Still, it seems the most persuasive argument to date.

To learn more about the biological basis of the female orgasm, click here:

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An international team of astronomers has conducted the biggest survey of stellar nurseries to date, charting more than 100,000 star-birthing regions across our corner of the universe.

Stellar nurseries: Outer space is filled with clouds of dust and gas called nebulae. In some of these nebulae, gravity will pull the dust and gas into clumps that eventually get so big, they collapse on themselves — and a star is born.

These star-birthing nebulae are known as stellar nurseries.

The challenge: Stars are a key part of the universe — they lead to the formation of planets and produce the elements needed to create life as we know it. A better understanding of stars, then, means a better understanding of the universe — but there's still a lot we don't know about star formation.

This is partly because it's hard to see what's going on in stellar nurseries — the clouds of dust obscure optical telescopes' view — and also because there are just so many of them that it's hard to know what the average nursery is like.

The survey: The astronomers conducted their survey of stellar nurseries using the massive ALMA telescope array in Chile. Because ALMA is a radio telescope, it captures the radio waves emanating from celestial objects, rather than the light.

"The new thing ... is that we can use ALMA to take pictures of many galaxies, and these pictures are as sharp and detailed as those taken by optical telescopes," Jiayi Sun, an Ohio State University (OSU) researcher, said in a press release.

"This just hasn't been possible before."

Over the course of the five-year survey, the group was able to chart more than 100,000 stellar nurseries across more than 90 nearby galaxies, expanding the amount of available data on the celestial objects tenfold, according to OSU researcher Adam Leroy.

New insights: The survey is already yielding new insights into stellar nurseries, including the fact that they appear to be more diverse than previously thought.

"For a long time, conventional wisdom among astronomers was that all stellar nurseries looked more or less the same," Sun said. "But with this survey we can see that this is really not the case."

"While there are some similarities, the nature and appearance of these nurseries change within and among galaxies," he continued, "just like cities or trees may vary in important ways as you go from place to place across the world."

Astronomers have also learned from the survey that stellar nurseries aren't particularly efficient at producing stars and tend to live for only 10 to 30 million years, which isn't very long on a universal scale.

Looking ahead: Data from the survey is now publicly available, so expect to see other researchers using it to make their own observations about stellar nurseries in the future.

"We have an incredible dataset here that will continue to be useful," Leroy said. "This is really a new view of galaxies and we expect to be learning from it for years to come."

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