Thanks to the tooth of a hunter-gatherer who lived 23,000 years ago in Granada, Spain, it has been shown that the Iberian Peninsula was the last refuge of the first settlers of Europe during the coldest period of the Last Ice Age.
The first Homo sapiens settlers of Europe arrived in an initial wave about 45,000 years ago, already well into the Last Ice Age. For about 15,000 years they were colonizing the continent, without too many problems. But between 25,000 and 19,000 years ago, all that was left of them was a small enclave in the south of the Iberian Peninsula.
Already the bones, and the technological styles of stone tools, seemed to indicate to experts that all of southern Europe had functioned as a refuge during the so-called Glacial Maximum, the coldest and harshest period of the last Ice Age.
But new discoveries point in the other direction. In particular, the analysis of the genes of an individual discovered in the Cueva del Malalmuerzo, in the Granada area of Spain. This human from about 23,000 years ago is the missing link between the last surviving populations of icy Europe, and those who would later repopulate the entire continent when the ice began to retreat about 19,000 years ago.
Today, thanks to paleogenetics, a piece of human bone is enough to know the history of a people. With the great technological advances, the genes that can be extracted work in almost the same way as when a historian discovers an old book.
The set of genes of the individual to whom the piece of bone belonged is known as the genome, and the information that can be extracted from it is as rich as a pile of books. But, the genes of a person not only tell their story, but that of all their ancestors.
Two recent studies, one published in the journal Nature, and the other in Nature Ecology and Evolution, have analyzed the genomes of 356 hunter-gatherers from all over Europe, covering a period from 35,000 to 5,000 years ago.
By comparing the genomes of different people with each other, it is possible to know the relationship of kinship between those individuals. In turn, this allows us to identify the route of the human species since it evolved in Africa about 300,000 years ago.
How it arrived in the Middle East about 100,000 years ago, settled in Europe about 45,000 years ago and, thanks to recent studies, how it almost became extinct on this continent during the last Ice Age, to repopulate it from the south of the Iberian Peninsula thousands of years later.
"Ancient genomes allow us to reconstruct migrations and population divisions that can be dated using purely genetic tools, based on diversity and mutation rates that are now widely accepted, after more than twenty years of the Human Genome," explains Carles Lalueza-Fox to Muy Interesante, an expert in paleogenetics and researcher at the Institute of Evolutionary Biology of the Spanish National Research Council and director of the Barcelona Museum of Natural Sciences.
"This approach must be done in collaboration with archaeologists, anthropologists and historians, in what undoubtedly constitutes a new and clearly multidisciplinary vision of the study of the past," the expert clarified.
The First Settlers
Our species, Homo sapiens, was not the first human to set foot in Europe. In the era that began to populate this continent, between 50 and 45 thousand years ago, it encountered Neanderthals. Encounters between both species had already occurred about 100,000 years ago, in the Middle East.
But Homo neanderthalensis had been in a significant demographic decline for tens of thousands of years, due to the harsh climatic conditions of the period before sapiens arrived in Europe. The last refuge of the Neanderthals, and where they finally became extinct about 40,000 years ago, was the Iberian Peninsula.
Although our species was better adapted to the drastic climatic changes that occurred during the last Ice Age, we will see that around 20,000 years ago the same decline that the Neanderthals suffered would begin in Europe, and their last refuge would also be the Iberian Peninsula. Only we survived, there and in other parts of the world.
Thanks to archaeology and paleoanthropology, different human cultures have been discovered in Europe from tens of thousands of years ago. Each with its own distinctive style of stone tools, cave art, stone and ivory carvings, etc.
With the help of genes extracted from bones from all over the continent, it has been possible to verify the relationship that existed between all these different cultures of Europe that cover a period of tens of thousands of years.
These human groups that began to arrive on the continent about 45,000 years ago carried what is known as Aurignacian culture, for the style of lithic tools they made. But around 33,000 years ago what is known as the Last Glacial Maximum began, a period of constant temperature reduction and a massive advance of continental glaciers.
At that time, technology had evolved into the so-called Gravettian culture, in what was until then a very interconnected European human population. Something very characteristic of this culture was cave art, and the large number of female sculptures they made. The most famous of these is the Venus of Willendorf.
But the advance of continental ice, accompanied by a constant reduction in temperature, led to an increasingly inhospitable climate. This pushed the populations towards the south, while atomizing them into isolated groups. Mainly in the Balkans to the east, in southern Italy, and to the west in southern France and southern Iberia.
This separation began to generate a new culture in what is now France and Spain, the Solutrean. After 20,000 years of inhabiting the continent, our species began to experience what had affected their Neanderthal cousins. An increasingly inhospitable climate, due to the arrival of the glacial maximum, was pushing them towards what would be their last redoubt: the south of the Iberian Peninsula.
Winter is Here
Humans were not simply seeking milder living conditions. The advance of the ice completely changed the climate, not only making it colder, but also making the air drier, affecting vegetation and fauna. In other words, human food.
Colloquially called the Ice Age, the Last Glacial Period gets both names from the incredible advance of continental ice. The global temperature was 6º lower than today, which may seem like little, but just one degree affects the climate and the circulation of air and water throughout the planet. As we are well aware of today with Climate Change due to Global Warming.
25 percent of the Earth's surface was covered by ice. This accumulation of water in its solid state at the poles and on the continents caused sea levels to drop 125 meters.
This in turn exposed large masses of land that were previously seabed, such as the English Channel. Europe suffered especially from the advance of continental ice, because this continent experienced more precipitation than other regions of the world.
The Last Glacial Period was part of what is known as the Quaternary Glaciation, which began about 2.5 million years ago. Within it, glacial and interglacial periods have alternated. The last of the glacial periods began about 115,000 years ago, until about 11,700 years ago, which began the interglacial period in which we live.
Although our species' adaptation to tolerate different climates allowed it to populate almost the entire planet during the Last Glacial Period, the period known as the Glacial Maximum was too harsh. It was the time when glaciers covered a quarter of the Earth's surface. It began to worsen about 33,000 years ago with its peak maximum between 26,000 and 19,000 years ago.
During this maximum, continental ice covered much of northern America, Asia, and northern Europe. The image we have of the Arctic today, a large white mass, came to cover northern France and Germany, leaving more than half of Denmark under ice, as well as Ireland, much of the British Isles, and the entire Baltic region.
With the exception of southern Italy, the Balkans, and the Iberian Peninsula, the other part of Europe that was not under ice was an Arctic steppe. Although these changes occurred over hundreds of years, they were too abrupt for plant and animal life, so they were pushed towards more equatorial zones, in some areas, while in others they were simply evicted.
The Last Refuge
It was already speculated that southern France and the Iberian Peninsula had been one of the only parts of Europe populated by humans during the Glacial Maximum, thanks to the abandonment that was seen in archaeological sites in various parts of the continent. But it is paleogenetics that definitively confirms this hypothesis.
"The Iberian Peninsula behaved like a genetic refuge that preserved, in part, the genetic composition prior to this climatic episode," explained Carles Lalueza-Fox, one of the authors of the study published in Nature Ecology and Evolution.
In that study, the remains of one of the survivors of that last Glacial Maximum were analyzed, who lived about 23,000 years ago in what is now Granada, Spain. It was discovered in the Malalmuerzo cave, a place widely decorated with high-quality cave paintings.
It is the first time that a member of the culture known as Solutrense has been genetically identified. They were able to compare it with other new genomes, and those of hundreds that were already known. This allowed them to discover the link that exists between the different cultures that populated Europe in the last 45,000 years.
The Aurignacian is the original inhabitant, which gave way to the Gravettian. The latter was the one that suffered the great onslaught of the Glacial Maximum. Many believed that it had disappeared, but paleogenetics proved that it continued in the Solutrense culture. Even modern-day Europeans carry in their DNA a genetic legacy of those last survivors.
"It had been seen in 2016 that the ancestry present in an Aurignacian from Goyet, Belgium, reappeared, albeit diminished, in a Magdalenian individual from El Mirón, Spain, but was not present in other parts of Europe," Lalueza-Fox said. "This persistence of more than 20,000 years was very surprising. Now, with the analysis of three Solutrense individuals, two from Spain and one from southwestern France, dated between 23,000 and 21,000 years ago, it has been seen that the Goyet ancestry persisted throughout the last glacial maximum."
"The populations that survived the glacial maximum in Iberia partly repopulated Europe and at the same time mixed with new populations that at the same time seem to come from the Balkans or the Near East," said the paleogeneticist.
"These latter make up the majority of the ancestry that we discovered in the populations of the Magdalenian culture. The panorama is still confusing in many details because, although we already have a couple of hundred genomes from all over Europe, there is a great complexity of migrations and changes that span more than 30,000 years," Lalueza-Fox concluded.
Comments
Post a Comment