from 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 at the local level… The impending heat, with unprecedented precocity, does not spare any region of France. In Arles, in Bouches-du-Rhône, the temperature of mercury did not fall below 23.9 degrees during the night from Thursday to Friday. The record for June is the month since the start of events in this city, in 1963, when the agency was not even one of the 37 placed on the orange or red vigilance.
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These extreme temperatures put pressure on our body. Difficulty falling asleep, fatigue, dehydration… But you need to get used to it: under the influence of climate change, heat waves are becoming more frequent. Are we used to living in such heat? Interview with Alain Froman, anthropologist and human evolution specialist.
Marianne: Will we be able to withstand the current temperatures?
Alain Froman: Yes, even if they threaten fragile people and are unpleasant. Some groups are accustomed to experiencing peaks of 40 degrees or more if they are well humidified. In fact, our species is more adapted to the heat than to the cold. We are of African descent, adapted to the climate of this continent. Evolving there, hundreds of thousands of years ago, we lost hair and developed evapotranspiration, the act of evacuating sweat to cool down.
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This is what allowed us to develop, for example, by chasing animals for food. Take an antelope: she runs much faster, but her body temperature rises quickly and she is forced to stop. On the contrary, we are slower, but we regulate our temperature, and therefore we can maintain the effort much longer. We make the game run and we end up triumphing! Our appearance is precisely determined by its ability to regulate temperature. Few animals do this: dogs breathe, but it is much less effective.
But the human race then got used to the cold …
Climate has always shaped our evolution. Man came from Africa and therefore adapted to other climatic conditions. Homo Erectus came to Europe 2 million years ago, then gave birth to Neanderthals, which evolved according to the lower temperatures of this continent. Then, from 100,000 to 60,000 years ago, modern humans, Homo sapiens, also migrated from Africa. They encountered Neanderthals. Mixing these populations has given Homo Sapiens genes that allow us to tolerate cold. Of course, there are also important cultural evolutions: wearing clothes, living indoors, fire… This is also part of our adaptation, even if it is not biological.
In the very long run, if temperatures continue to rise in the coming decades, can this drive the evolution of our species?
Humanity has not stopped evolving, far from it! We are constantly adapting to our environment. In the Neolithic era, 7,000 years ago, we inherited genes for milk digestion and others for alcohol metabolism. There are no theoretical barriers to mutations appearing and then gaining an advantage if they allow us to adapt to global warming. Especially since there are 7 billion of us: the probability of mutations is high!
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On the other hand, these evolutions inevitably take a long time. It takes thousands of years for a mutation to be isolated and then spread. But until then, the climate may change. We are in the interglacial period, at the end of which the mercury will fall again, perhaps before these evolutions of our species.
Is it possible to predict how our organisms would have evolved if we had passed tens of thousands of years that came with a few more degrees?
Although the question of morphology depends on many factors, we know that hot and dry climates tend to prefer large sizes. On average, Nilot peoples living in East Africa are tall and thin, but these are populations that have very few non-African genes. This allows them to have a larger skin surface area and more sweat to dissipate heat and stay at 37 degrees. On the contrary, the Inuit need to warm up: their limbs are shorter and their chest is wider. This is the climate that dictated these evolutions, visible to the naked eye! Perhaps a person will get taller and taller to withstand the heat.
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The skin color of Europeans, by contrast, is unlikely to darken. The increase in temperature is not associated with an increase in sunlight and, consequently, ultraviolet radiation, but with the greenhouse effect. But the dark color protects against ultraviolet radiation: if it is no more, you do not need to protect yourself.
In the very short term, on the other hand, it is better to rely on the adaptation of our behavior!
Yes, these are very long mechanisms, and not on the scale of human life. But we can adapt through our behavior. The heat of 2003 caused a hecatomb, as this phenomenon was still new. Fragile people, especially the elderly, were encouraged to drink, but without salt, which does not provide effective hydration. Now we know more about human physiology: heat waves cause far fewer victims!
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Man has always adapted to his environment through his culture, it is part of his evolution. Let’s take chimpanzees: they have big fangs, which we lost because we invented flint. You don’t need these big teeth! Human evolution is also the invention of solutions, prostheses.