Why did the modern man lose the fur that his ancestors covered?
A long time ago, we naked great apes gave up most of our body hair. Every day millions of people ask in front of a mirror why am I hair?
Millions of dollars are spent annually on waxing, eyebrow shaping, laser hair removal, face and leg smoothing, plus the money spent on neighborhood salons and professional hairdressers?
But our question turned out to be wrong, at least according to scientists studying human genetics and evolution. The biggest puzzle for them is our hair loss.
Evolutionary theorists have put forward many hypotheses about why humans have turned to bare skin in the primate world.
Was that an adaptation for semi-aquatic environments?
Does our bare skin help us sweat; So stay cool while hunting on a hot day?
Did losing our fur help us read other people's emotional responses like anger and redness?
Scientists don't know for sure, but biologists are beginning to understand the physical mechanisms that make humans a naked monkey.
A recent study, published in Cell Reporters, began solving the mystery at the molecular and genetic level. Sara Mello, author of the main new study and professor of dermatology in the medicine class at Perlman University - Pennsylvania, explains the confusion of scientists in explaining why patterns of feeling vary across human bodies. “We really have long hair on our scalp, and short in other areas,” she says. We have no hair in the palms of our hands, the lower part of our wrists, and the insides of our feet. Nobody knows exactly how these differences originated. ”
In many mammals, there is a hairless area known as the "plantar skin" and is similar to the bottom of the wrist and feet in humans. However, some species such as: rabbits and polar bears are an exception. As the fur coats her bottom. While studying the plantar region of rabbits, the researchers noted the absence of high levels of an inhibitory protein called (Dickkopf 2) or (Dkk2), indicating its primary role in hair growth.
When researchers looked at the mice's bare plantar region, they found high levels of Dkk2, which suggested the protein's role in keeping patches of skin without hair. By blocking the pathway of the so-called signals (WNT) that controls hair growth.
To illustrate, the team compared the evolution of normal mice with another group that had a mutation that inhibits the production of the Dkk2 protein. They found that the transgenic mice had hair growing on the skin of their sole. This gave more evidence for the role of this inhibitory protein in identifying bare areas of the fur.
But Dkk2 isn't the end of the story, according to Miller. Hair growing on the skin of the plantar region of GM mice is shorter, smoother, and less uniform than that of other animals.
“Dkk2 protein is sufficient to stop hair growth, but not to eliminate all control mechanisms,” she says. There is a lot to look at. ” Even without the complete picture, the findings could be very useful for future research in other areas such as baldness; Once the WNT pathway is present in the dome of the chromosome, it is blocked by Dkk2 or similar inhibitors in humans.
"Understanding how the suppression system works may help research other skin conditions, such as psoriasis and vitiligo that cause discolored patches of skin," Miller says.
Why did modern humans lose the fur that their ancestors covered - hypotheses about why humans turned to bare skin in the primate world - the reason for body hair - hair growth
Reconstruction of the head of the human ancestor the Australopithecus afarensis, an extinct Homo erectus that lived three to four million years ago. The famous and lucky skull belonged to the genus Australopithecus afarensis.
As the understanding of the mechanism of skin-striping increases, the big question remains, why did a completely human become a hairless monkey?
Miller says: “There are clear reasons, for example, that the presence of hair on the palms of our hands and our wrists makes the use of stone tools, or the use of tools very difficult, and thus the lack of it was an additional advantage of human ancestors without hair. As for why we lost the rest of our pharaohs, it has been a matter of debate for decades.
The water ape hypothesis is a popular and favorite idea. This hypothesis suggests that human ancestors lived in the African savannah, hunting prey, but moving in dry seasons to oases and lakes shores, crossing shallow waters. To collect water tubers, shells or other food sources.
According to the premise, since the hair is not a good insulator in water; Our species lost its fur and developed a layer of fat. The theory even suggests that we may have developed two-legged walking; Because of its benefit in wading shallow waters. This decades-old idea has not received much support from the fossil record, and many researchers have not taken it seriously.
According to another widely accepted theory, human ancestors developed a new way of regulating heat as they moved from cold shady forests to savannahs. Losing all this fur allowed them to hunt in broad daylight in the hot grasslands, avoiding their overheating.
The increased number of sweat glands in early humans ensured their survival on the cold side, outperforming other primates. The evolution of fire and clothing also enabled him to stay cool in the day and warm at night.
But these are not the only possibilities; Hair loss may be caused by a combination of factors.
According to University of Reading evolutionary Mark Pagal, fur loss also reduces the impact of lice and other parasites.
Humans kept some patches of hair, like the top of our head; To protect us from the sun, and the pubic area to keep our pheromones secreted. “The more hair we lose, the more attractive we become,” Bajel adds. Hair loss is strong evidence of health, parasite-free. ” According to one of the most interesting theories, loss of facial hair and some genital area hair helped with emotional communication.
"Perhaps the cause of our hair loss lies in our eyes, as while many animals have two pairs of cones, or the receptors in the color-revealing eye, humans have three," says Marc Changezi, an evolutionary neurobiologist and director of cognition at the Research Foundation 2AI, who studies vision and color. .
Other animals with three or more pairs of cones in their eyes, such as birds and reptiles, have a wide field of vision from wavelengths in the daylight spectrum, but our third cone is unusual. It gives us additional power to determine the correct shape in the middle of the spectrum, enabling people to select a wide range of shades that seem unnecessary for hunting or capturing.
Changhisi proposes the role of the third cone in non-verbal communication by making changes in the color of the face. “Having these two cones with specific wavelengths side by side is what we need to be sensitive to subcutaneous hemoglobin oxygenation; To realize health or emotional changes ». For example, green or blue children's skin color may indicate disease, while reddish-pink is a sign of sexual temptation, as for the pink and redness of the face, it is a sign of anger - and this includes dark-skinned people - but the only way to see all these emotional states is to lose Humans have their own body fur, especially the face.
In one of the papers published in 2006 in the Living Letters, Changhesi found the tendency of bare-faced primates, and sometimes their buttocks, to have three human-like cones, compared to the two cones of barny-faced monkeys. Nude faces and color vision are associated, according to this paper.
According to Miller, this work probably won't help us deduce whether humans are swimming monkeys, sweaty monkeys, or even shy primates. But the merits of the new study on hair growth with the characteristics of the human hairy body may bring us closer to the truth, or at least enable us to get thicker and shinier hair.
