Cheddar man: why did the humans who left Africa have their skin cleared thousands of years ago?
The study of the oldest human skeleton found in the United Kingdom contradicts the popular belief that most Europeans always had light-colored skin.
A genetic analysis of the known as "man of Cheddar", 10,000 years old, revealed that the pigmentation of his skin was "dark to black."
"The combination of very dark skin with blue eyes is not what we typically imagine, but that was the real appearance of those people," said Chris Stringer, of the Museum of Natural Sciences in London where he was exposed on Wednesday.
In fact, according to Yoan Dieckmann, of the University College London team responsible for the study, the light skin we associate with modern northern Europeans would be a "relatively recent" phenomenon.
So when did those ancestors begin to change their skin color and why did this phenomenon occur?
According to experts, there are two main factors that explain this historical transformation.
The first of these is the geographic mobility of modern human populations, which while living in Africa at least 150,000 years ago were mostly dark skinned.
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"Those populations, which would be our direct ancestors, then began to migrate, to Europe, for example, they arrived some 45,000 years ago," Víctor Acuña, a professor at the National School of Anthropology and History of Mexico, told BBC.
Some genetic studies concluded that the clearest skin pigmentation began to be common in some European regions 25,000 years ago.
The discovery of the "Cheddar man", who lived 10,000 years ago, however, indicates that this clearing did not occur until much later in places like the British Isles.
The analysis in 2014 of other human remains from 7,000 years ago found in León, Spain, also concluded that they belonged to a man with dark skin and blue eyes.
Protection against the sun
The second factor, the most important, is the one that explains why when reaching these areas of the planet the skin of humans tended to clear up.
"Humans, unlike other primates, have very little body hair(vello), so we thought that skin pigmentation was a barrier to the negative effects of ultraviolet light" so intense in Africa, Acuña said.
When they migrated to regions of the north of the planet, where the radiation of the sun is much scarcer, they no longer needed that natural protection against possible burns （quemaduras） or skin cancer.
As Acuña explains, "in areas with little sun, having lighter skin color allowed them a better absorption of ultraviolet light that is vital to better capture vitamin D".
This explains why within Europe itself differences began to be observed. The lighter skins became more frequent in the north, while in the south the population showed more variable tones.
In short, the skin color played a fundamental role at the time that those generations could adapt to the environment in a natural way.
10% of those ancestors
With this explanation, it is obvious that this characteristic of human evolution is not reduced only to the ancestors of the British.
In fact, as Acuña points out, this trend towards an increasingly clear pigmentation was not only recorded among the ancestors who arrived in northern Europe.
"Studies indicate that similar evolutionary processes occurred at least in the populations that arrived in East Asia and Africa, where, despite what many people believe, there were also notable differences in the pigmentation of their skins," said the professor.
On the finding of the "man of Cheddar", the expert confirmed the direct relationship between that ancestral group and the current European population, although he added that the latter could be the carrier of no more than 10% of those ancestors due to miscegenation.
"That first population had contact with subsequent migrations, which made them 'disappear' as an archaeological culture when they were assimilated by other groups," he told BBC Mundo.
It is estimated that the "Cheddar man" migrated from continental Europe to the British Isles at the end of the last Ice Age.