Feb 17, 2023 21:00:00

Research results that human beings have hair ``because it is cooler to have hair''

Unlike other mammals, human beings have thin hair all over the body, and a large amount of hair is dense only on parts of the body such as the top of the head, and some people have curly hair instead of straight hair. There are several hypotheses on the question 'Why do humans have hair, and why do some people have curly or curly hair?' An unpeer-reviewed paper on

bioRxiv , a preprint server, suggested the conclusion that 'humans are cooler with hair, especially curly.'

Human scalp hair as a thermoregulatory adaptation | bioRxiv
https://doi.org/10.1101/2023.01.21.524663

Cool New Experiment Explains Why We Evolved Curly Hair : ScienceAlert
https://www.sciencealert.com/cool-new-experiment-explains-why-we-evolved-curly-hair

Scientists have been studying the reason why 'hair' exists in human beings for decades, and in a 1988 study , 'bald people sweat two to three times more than people with hair. It is easy to use and suitable for keeping your head cool.' However, a 2010 study showed that ``bald heads sweat more easily because they absorb more heat, and as a result, they just sweat more''.

Therefore, a research team at Pennsylvania State University and Loughborough University used

a thermal mannequin that can reproduce the temperature of the human body and study thermal radiation, etc., and a wig made of human hair, to determine the presence or absence of hair and the heat of the human body. I studied the effects on radiation.

The research team set up a thermal mannequin in a temperature- and humidity-controlled room, exposed it to sunlight that reproduced the sun, and collected data on the body temperature and thermal radiation of the head. In the experiment, the mannequin was covered with wigs of various hair qualities such as straight, loose curls, and tight curls, and the scalp was exposed without covering the wig, and the changes at different wind speeds were also analyzed.

Experiments have shown that wig-covered mannequins absorb less heat than non-wig mannequins and require less sweat to regulate body temperature. Furthermore, it was also found that curly hair has a larger gap between the hair and the scalp than straight hair, which increases air permeability and reduces sweating.

The research team said, ``In this study, it was confirmed that hair functions as a barrier that reduces heat loss from the body (here, the scalp) to the surroundings, regardless of hair type.'' ``Strongly curled hair 'It can reduce heat influx more than straight mammalian hair.'

The results of this study suggest that human beings began to walk upright on two legs and that hair evolved in response to brain enlargement. The researchers found that 'the emergence (or maintenance) of hair is optimal for maximizing heat loss over large areas of the body while minimizing solar heat absorption on the small surface of the head, the scalp, just above the brain.' We may have achieved a nice balance.'

Science Alert, a scientific media, said, ``Of course, the situation of placing a mannequin in an air-conditioned room is not completely realistic.In order to investigate how hair has evolved, more Further research with human subjects outdoors in a natural environment is needed, but the results of this experiment suggest that human hair is more suitable for bipedal living, especially in hot and dry climates where drinking water is scarce. It lends credence to the hypothesis that it evolved to adapt.'