Fur? Yes, if we go back a little (a lot) in time, we realize that in prehistoric times, the first men were very hairy, they even had fur.
How did the transformation take place up to the present man? What are the reasons for this evolution? You will know all about the evolution of man and especially his hair.
Originally, in Africa…
The loss of fur began in Africa more than 2 million years ago. The first Homo Erectus are forced to travel great distances in search of food. Also, the environment around them is also increasingly open. The system of perspiration that is put in place is more and more efficient and the fur gradually gives way to a human coat that will prevent them from being too hot, especially with the extra activity of their new way of life. But the progressive loss of this fur is not only due to the too strong heat felt and has other more complex origins.
For Darwin, the loss of this important fur would be due to sexual selection. Our ancestors already seemed to have preferences for less hairy partners, which would have led to evolution in this direction. In these conditions, removing fur was essential for the survival of the species. If humans prefer to have partners with less hair, then they must be satisfied in order to maximize the chances of reproduction.
Thermoregulation without fur
The main cause remains mainly a concern for thermoregulation. Several factors come into play. A climate change that will replace the humid forests in which men were sheltered by particularly dry plains and savannas. Thus men found themselves exposed to heat. On the other hand, man is in full evolution and is beginning to stand upright and walk with both legs. This makes them expend more energy than before.
All the more so as they are obliged to move further and further away to find food which is also displaced by the change of environment that is taking place. All this would have led to a strong overheating if the fur had not disappeared. It is the whole system of perspiration that will also appear at this same period, allowing a significant cooling of the body. The appearance of the sweat glands will allow the evaporation of perspiration for thermal regulation. Nowadays, only people suffering from hypertrichosis are left with fur!
Removing the chimpanzee
At that time, monkeys and humans are very similar, but that will change from this evolution on hair. If at first we see the same density of hair follicles in man and chimpanzee, this will change. The hair will become thinner and thinner. But the big difference is in the density of the sweat glands, which are distributed throughout the body. These glands are ten times more present in humans.
Adapting to the new savannahs
One can imagine that during this period of change (between the last common ancestor with chimpanzees and the appearance of Homo sapiens, between 9 million and 300,000 years before our time) it will have been necessary to adapt to the new environment. So man began to walk, but he remained an easy prey. We can therefore imagine that he will have tended to go hunting in the savannah at the hottest hours while the fiercest animals remained in the shade. This new way of life has encouraged hair loss. An evolution that will also bear fruit since it will give man the advantage of being able to hunt his prey for long hours in the heat thanks to an efficient thermal regulation system. Man then has the advantage over animals that do not have this ability.
Reduction of fatal diseases
A complementary hypothesis brought by the English biologist Mark Pagel adds another virtue to the disappearance of fur other than that of thermal regulation. It would also have made it possible to reduce the number of body parasites (flies, ticks, mosquitoes and lice) commonly found in mammalian fur and which are vectors of potentially fatal diseases. Another good way to keep the human species alive!