Study of ancient genomes explains how Europeans became white

In the midst of the Syrian refugee crisis, which has affected much of Europe in the past decade, German biochemist Johannes Krause decided it was time to retell the continent’s deep past based on the findings of genomics, in particular what is known about the DNA of people who lived thousands of years ago.

The result is the book “The Journey of Our Genes”, which he co-wrote with science journalist Thomas Trappe. The work brings two clear messages to those who see something apocalyptic in the migratory flows from poor countries to Europe.

First, it shows that far from being ‘racially pure’, Europeans today derive from a series of miscegenations of very different groups. The book also points out how compared to these past events, today’s immigrants are just a drop in the ocean.

“We wanted to show that, to begin with, mobility is part of human history. Secondly, the arrival of 1 million Syrians in Germany is a very small thing compared to what happened in the past, and we always deal with phenomena of that kind,” Krause told Sheet in conversation by videoconference.

“And it’s something that goes for very recent historical periods as well. Look at what happened in Germany after World War II — the country took in 15 million workers from Turkey, Greece, Italy and elsewhere. and it actually helped our economy.”

Advances in DNA sequencing (roughly, “spelling”) techniques and the ability to reliably recover genetic material from ancient skeletons have helped Krause and his colleagues at the Max Planck Institute for Evolutionary Anthropology to trace a detailed chronology of the comings and goings. population arrivals from Europe from about 50,000 years ago, when the first members of our species began to arrive on the continent.

In the middle of the Ice Age, huge climatic fluctuations and the rigors of the cold caused a good part of Europe’s original settlers to perish, while other waves of Homo sapiens arrived on the mainland and also suffered from the climate. But a few of these pioneers survived, forming the first major ancestral component of the European genome, that of Stone Age hunter-gatherers.

Interestingly, although this group contained many light-eyed people, their skin was dark, the DNA indicates, showing that today’s racial categories do not serve to describe peoples of the past. “We have evidence that only in the extreme northeast of present-day Europe there were already pale-skinned hunter-gatherers around 10,000 years ago,” says Krause.

It turns out that lighter skin tones usually evolve in populations native to areas with relatively weaker sunlight throughout the year, far from the equator. In these circumstances, natural selection may favor fair skin because it facilitates the action of sunlight in the body’s production of vitamin D, which is essential for health and development.

However, it appears that this is only necessary if people do not have access to dietary sources of vitamin D, such as fatty fish (salmon) and liver. European hunter-gatherers were able to obtain food of this type in sufficient abundance, which explains why they spent many thousands of years without losing their dark skin tone.

Ironically, Europeans only started to become “white” with the arrival of immigrants from present-day Turkey, starting around 8,000 years ago. They were people who had already become dependent on agriculture, which offered a more restricted diet, based on cereals such as barley and wheat and with less vitamin D, hence the change.

Although their food was of poorer quality, on average, newcomers from the Near East were able to support a much larger population thanks to the productivity of their crops. This caused them to slowly replace most hunter-gatherer groups over the next few millennia, interbreeding with what remained.

In some places in the present-day Mediterranean, such as the island of Sardinia off the Italian coast, all inhabitants are still basically descended from Anatolian farmers.

The last major turning point in the European genome began some 5,000 years ago, with the arrival of highly mobile pastoralist groups that initially lived in the Black Sea steppes, on the border between present-day Ukraine and Russia.

With technologies such as the wheel, the use of bronze to make weapons, and the domestication of horses, steppe immigrants set off a similar process of substitution and miscegenation.

It is very likely that they were the original speakers of the language known as Proto-Indo-European, the ancestor of almost all current European languages, from Portuguese and English in the west to Russian and Lithuanian in the east.

These same groups also invaded present-day Iran and India, giving rise to many of the languages ​​of these countries.

“Both the agriculture of the Anatolians and the new technologies of the steppes were huge changes in the economy and society. Also, the population density was relatively small, so it makes sense that they profoundly transformed the population that existed on the continent. After the Bronze Age , it became much more difficult for that to happen. The migrations continued to happen, but the impact was proportionally much smaller”, explains Krause.

The researcher collaborates with a Brazilian team led by André Strauss, from the Museum of Archeology and Ethnology at USP, and is due to visit Brazil in November. The partnership has already made it possible to analyze the DNA of some of the oldest inhabitants of the country, the population of Lagoa Santa (MG), which is around 10,000 years old. “We are also interested in working with more recent populations in the Amazon,” he says.

“The Journey of Our Genes”

authors Johannes Krause and Thomas Trappe
Translation Maurício Mendes da Costa and Vanessa Rabel
Publishing company Sextant
How much BRL 54.90 (printed); BRL 39.99 (ebook); 288 pages