Will our bodies get used to extreme temperatures over time?

37 to 40 degrees Celsius in Occitania, New Aquitaine or the Rhone Valley; From 35 to 39 degrees in Poitou and Vendée, with even higher temperatures in some places… The heat wave, which emerges with unprecedented precocity, does not spare any region of France. In Arles, in the Bouches-du-Rhone, the mercury did not drop below 23.9 degrees overnight from Thursday to Friday. A record for the month of June since the beginning of events in this city, in 1963, when the department was not even one of the 37 placed on orange or red vigilance.

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These extreme temperatures put our body under pressure. Difficulties with sleep, fatigue, dehydration… But it takes getting used to: under the influence of climate change, heat waves are becoming more and more frequent. Will we eventually get used to this heat? Interview with Alain Froment, anthropologist and specialist in human evolution.

Marianne: Will we be able to withstand the current temperatures?

Alain Froment: Yes, even if they pose a danger to fragile people and are unpleasant. Some people are used to experiencing peaks of 40 degrees or more, as long as they are well hydrated. Indeed, our species is more adapted to heat than to cold. We are of African descent, adapted to the climate of this continent. During evolution there, hundreds of thousands of years ago, we lost our hair and developed evapotranspiration, the process of removing sweat to cool ourselves.

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This is what allowed us to develop, for example, chasing animals for food. Take an antelope: it runs much faster, but its body temperature quickly rises and it has to stop. On the contrary, we are slower, but we regulate our temperature, and therefore we can withstand the effort much longer. We make the game race and ultimately win! Our species is precisely defined by its ability to regulate its temperature. Few animals do this: dogs pant heavily, but it’s much less effective.

But humanity then got used to the cold …

Climate has always determined our evolution. Man came out of Africa and therefore adapted to a different climate. Homo Erectus arrived in Europe 2 million years ago, then gave rise to the Neanderthals, who evolved to suit the colder temperatures of that continent. Then, from 100,000 to 60,000 years ago, modern humans, Homo sapiens, also migrated out of Africa. They encountered the Neanderthals. The mixing of these populations gave Homo sapiens the genes to endure cold. Of course, there are also important cultural evolutions: wearing clothes, living indoors, fire … This is also part of our adaptation, albeit non-biological.

In the very long term, if temperatures continue to rise in the coming decades, could this affect the evolution of our species?

Humanity has not stopped in its development, far from it! We are constantly adapting to the environment. In the Neolithic age, 7,000 years ago, we acquired genes for digesting milk and others for metabolizing alcohol. There are no theoretical barriers to mutations appearing and then favored if they allow us to adapt to global warming. Especially since there are 7 billion of us: there is a high probability that mutations will occur!

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On the other hand, these evolutions inevitably require a lot of time. It takes thousands of years for a mutation to be chosen and then spread. But by then the climate may have changed. We are in an interglacial period at the end of which the mercury column will drop again, perhaps before this evolution of our species occurs.

Is it possible to predict how our organisms will develop if we live tens of thousands of years, which come with a few more degrees?

Although the question of morphology depends on many factors, we know that hot and dry climates tend to favor large sizes. On average, the Nilotic people of East Africa are tall and lean, but these are populations characterized by the presence of very few non-African genes. This allows them to have more skin surface area and sweat more to wick away heat and stay at 37 degrees. On the contrary, the Inuit need warmth: their limbs are shorter and their chest is wider. It was the climate that dictated these evolutions visible to the naked eye! Perhaps the person will grow taller and taller to withstand the heat.

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The skin color of Caucasians, on the contrary, is unlikely to darken. The increase in temperature is not due to an increase in the amount of sunlight and, therefore, UV radiation, but to the greenhouse effect. But the dark color protects against UV: if there is not more of it, you do not need to protect yourself.

On the other hand, in the very short term it is better to expect our behavior to adapt!

Yes, these are very long mechanisms, and not on the scale of human life. But we can adapt through our behavior. The 2003 heatwave caused the hecatomb because the phenomenon was still new. Frail people, especially the elderly, are forced to drink, but without salt intake, which does not allow effective hydration. Now we know more about human physiology: heat waves cause far fewer casualties!

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At all times, Man has adapted to the environment due to his culture, this is part of his evolution. Take chimpanzees: they have big fangs, which we lost because flint was invented. Don’t need those big teeth! Human evolution is also associated with the invention of solutions, prostheses.