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One of the more striking differences between humans and his ape-like cousins is his hairlessness. Apart from head hair and patches of hair on hidden body parts people are naked. Charles Darwin was puzzled by this and writes in The Descent of Man: “No one supposes that the nakedness of the skin is any direct advantage to man; his body, therefore, cannot have been divested of hair through natural selection”.

Modern investigators though have been looking for evolutionary answers. Based on certain historical and medical assumptions, they’ve come up with the following theory.

It all began about 1.5 million years ago when man with its upright gait began to inhabit the savannas. There he used his running ability to hunt for bigger game, an activity that made him sweat a lot. His hairy body wasn’t very helpful because it prevented fast evaporation and thus the necessary cooling effect. This caused an evolutionary advantage in losing most of his hair and an increase of associated sweat glands.

Very probably these predecessors of Homo sapiens had white skin, just like chimpanzees still have under their fur. Under the blazing African sun this was a major disadvantage. Nowadays still African Albino individuals die young of skin cancer. Therefore, the evolutionary pressure of skin pigmentation has been strong and has created the typical African ‘race’[1]. The reverse has taken place much later when people started to inhabit parts of the world with colder climates.

Long before Homo sapiens came to Europa the Neanderthals had been roaming around in Eurasia for some hundreds of thousand years. There was lots of time then to develop a lighter sin tone and straight hair. This human species became extinct about 40.000 years ago, but not after reproducing with H0mo sapiens. Much of the reconstruction images are more based on bone and skull remains than on DNA (see image above).

Science doesn’t have a plausible idea about the development of frizzy hair that still is a characteristic of people of African origin. One explanation is that this hair texture acts as a mechanism that enhances air flow. Therefore it regulates the temperature of the brain better than straight hair or no hair at all, especially in hot climates.

When people moved to colder and wetter climates the developing of straight hair functioned as a means to let water run down easily and to retain body heat.

And why do women have less body hair than males? Different theories about the evolutionary advantage have been proposed, without any biological proof by the way. One I find plausible is that the loss of human body fur had its origin in the ancestral mother-infant relation. The loss of body hair gave rise to the pleasure of skin-to-skin contact with the infant, which in turn encourage the mother to bear the infant. This would also explain why children are more hairless than adult males. This maternal selection for hairless infants was then reinforced through primarily male sexual selection for a hairless partner.

Another theory is that more hair would attract more parasites that could be dangerous for the mother as well as the child.

Reconstruction of a girl from 5700 years oold DNA found in Northern Europe

Reconstruction of a young girl based on 5700 years old DNA found in  Northern Europe.

Skin color, the degree of pigmentation in the development of Homo sapiens, is a subject that lately has been clarified by DNA testing on thousands of years old remains of northern Europeans[2]. We assume that skin color is an adaptation to the environment, in this case, the prevailing UV radiation. This radiation is basically harmful but promotes the formation of vitamin D, necessary for bone formation. In a climate with plenty of sunlight, dark skin will pass enough UV radiation to form that vitamin. When the probably hairless African Homo sapiens shifted living in the woods for the savannas, a dark complexion (as previously explained) was necessary for survival. In more northern areas outside Africa, this had a disadvantage instead. When the Europeans and Asians later, after the last ice age around 10,000 years ago also reached the region of the high North, evolutionary pressure beneficiated mutants with lighter skin color. Protective clothing against the cold enhanced this process. The subsequent depigmentation process took a few thousand years. It also resulted in blue eyes and blond hair. Depigmentation had previously taken place in tribes north of the Black Sea, such as the Yamnaya people that migrated to the West 5,000 years ago and mixed with the inhabitants of central and southern Europe. This explains, in a nutshell, the skin color differences that still influence the view of human beings.

[1] A gene responsible for a darker skin (MC1R) was already present in the genome of Africans 1.2 million years ago (Current Anthropology, 2004, Vol.45, nr.1).

[2] Conclusions from DNA-investigations, published in Nature, June 10, 2015.