Science

Is sex good for anything other than procreation? – Science and the future

“What is sexual intercourse for, besides reproduction?” asks Cedar Senghor on our Facebook page. This is our reader’s question of the week. To answer it, (re)open below our interview on this topic with Thierry Lode, Professor of Evolutionary Ecology at the University of Rennes 1, originally published in Les Indispensables de Sciences et Avenir No. 208 January/March 2022. Thierry Lode explains, in particular, that sexual intercourse brings pleasure, which plays a role in the regulation of social life.

“Reproduction doesn’t need orgasm, and sexual satisfaction doesn’t need reproduction.”

Sciences et Avenir: when did pleasure appear in the history of life?

Thierry Lode: To establish this, you need to look at the definition of orgasm, the organic manifestation that can be found in the experience of sexual pleasure. In the 1970s, it was discovered that macaques felt it, only to realize that many vertebrates have the physiological ability to achieve it!

In humans, orgasm is associated with ejaculation or expulsion of fluid, rhythmic muscle contractions of the muscles of the perineum, retraction of the clitoris, convulsive contractions of the perineum and vagina. But the main key to understanding its origin lies in the fact that it is accompanied by a discharge of neurons with the release of neurohormones: endorphins, dopamine, oxytocin … This is expressed in the culmination of sexual arousal, activating the neural circuit of reward. Therefore, it certainly settled with or immediately after the invention of the nervous system, in the Cambrian, about 540 million years ago.

Does orgasm have an evolutionary advantage?

Reproduction does not require an orgasm, and sexual satisfaction does not require reproduction… The claim that the female orgasm promotes procreation remains highly controversial, as it does not appear to play an active role in the transport of spermatozoa during intercourse and may even interfere with him. Moreover, the increase in copulation and seduction behavior in most species, including females, seems to disprove the fact that it has the function of strengthening love bonds. Therefore, it is difficult to understand selective interest.

But we know that the senses – smell, taste, touch – help to choose a sexual partner that is different from oneself, compatible at the immune level and enhances the heterogeneity of the genome. In addition, internal fertilization, a mode of reproduction that appeared 300 million years ago, has significantly reduced the number of offspring as evolutionary innovations have taken place. While the cod scatters millions of eggs, the frog lays only a few hundred, and the female gives birth to only one fawn. The persistence of orgasm stems from this drastic reduction: by associating pleasure with the act of reproduction, the species compensated for it by increasing the number of matings. Thus, a leopard can mate 150 times in one day.

“Pleasure plays a role in the regulation of social life”

How does it represent the engine of evolution?

Sex remains the worst solution to the problem of reproduction, and is preferred primarily because it allows for genetic mixing and is permanently fixed in the body through ecstasy. Pleasure is contained in the flow of molecules that flood the neural circuits, evoke emotions, and play nuances in desire and feeling. By spreading emotional and sensory pleasure, the brain thus became the first sexual organ.

On a larger scale, pleasure plays a role in the regulation of social life, as evidenced by caring for others, such as caring for primates. A secret desire for general well-being mixes gradients of pleasure and eroticism with all evolution. Which supports an alternative paradigm to Darwin’s, that of evolutionary ecology: the engine of evolution lies in the structuring power of interactions. Pleasure is not only a product of evolution, but also one of its main engines.

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