Curly hair surely had a decisive role in human evolution

Reading time: 2 min — Spotted on National Geographic

Faced with this curly and indomitable mane, unable to offer you the wick of Justin Bieber, you grumbled a lot as a teenager. The curls, it’s true, are sometimes heavy to carry: the weight of the human race…

In any case, this is what the results of a study led by Tina Lasisi, a researcher in biological anthropology at Pennsylvania State University, would reveal, which shows that curly hair offered better brain protection to hominids (men prehistoric), thus guaranteeing them a better chance of survival.

National Geographic discusses the ins and outs of the research, which could even make curly hair one of the reasons why homo sapiens supplanted other hominid species like the Neanderthals and Denisovans who went extinct there. about 40,000 years ago.

Protecting a boiling brain

Understanding why humans have hair is still a matter of debate among scientists. To answer the question, Tina Lasisi and her colleagues started from an initial observation: “The brain is a large organ, very sensitive to heat, while also generating a lot of it. So we said to ourselves that at a time when we see that the size of the brain of our species is increasing, the capillary mass could be decisive from an evolutionary point of view.

The scientist explains that “Scalp hair spares us the physiological cost of sweating.” This is indeed not without consequences, since these secretions made to regulate body temperature cause us to lose water and electrolytes (minerals) at the same time. “For our hominid ancestors, this could have been crucial.”

To verify their hypothesis, the team from the University of Pennsylvania used a thermal mannequin, wearing three different wigs (straight, moderately curly, very curly). The dummy was put to the test of various climatic and meteorological conditions approaching those encountered by the first hominids. In this way, scientists were able to measure how hair regulates the temperature of the scalp when faced with direct sunlight, rain, wind, etc.

While the results found that all hair types offered some protection from the sun, the curliest hair was found to provide the best cranial protection. In addition, they better protect the scalp from solar radiation and do not lie flat against the skin when wet. “It is an important discovery”welcomes Professor Lasisi, who nevertheless invites us to deepen genetic research.

At a later stage in our evolution, indeed, curly hair may have lost its evolutionary advantage and straight hair may have been favored by different types of genetic selection. “Maybe once we had these bigger brains, we also had all these cultural adaptations to avoid overheating, like better sources of watershe supposes. By then, there may have been no more selective pressure for curly hair.” Will frizz come back with a vengeance when global warming has taken its toll?