The genomic revolution, which has been modifying much of what we thought we knew about human history, has affected studies on the peopling of America in a paradoxical way. On the one hand, DNA analyzes seem to have resolved some centuries-old controversies once and for all, but they also ended up creating a series of new puzzles.
Both the consensus and the mysteries are explained with great didacticism and balance in the book “Origin: A Genetic History of the Americas”, written by Jennifer Raff, from the Department of Anthropology at the University of Kansas (USA).
On the consensual side, the genomic and archaeological evidence presented by the researcher makes it clear that the first inhabitants of our continent descend mostly from groups that, a few tens of thousands of years ago, lived in Siberia.
Some of these groups managed to cross from the Old to the New World, passing through the frigid regions of the Arctic, probably after living for many generations in the so-called Beringia. This name designates the regions around the lands now submerged in the Bering Strait (between Siberia and Alaska), but which were above sea level during the Ice Age, when much of the planet’s water was “sequestered” in glaciers.
Beringia, then formed by a steppe that was home to large mammals such as mammoths and woolly rhinos, was immense. It is estimated that the land bridge between the continents may have reached 1,000 km in width and 1.6 million square kilometers in area.
Many researchers believe that the distribution of glaciers on the continent and in the oceans prevented residents of Beringia from reaching territories south of Alaska during the so-called Last Glacial Maximum, phase of the Ice Age that ended 19,000 years ago.
After that, they would have started a relatively rapid expansion by sea, first going down the Pacific coast and then internalizing their occupation of the mainland, argues Raff in his book.
This would explain, among other things, the relatively high genetic similarity between a child who died in the US state of Montana 13,000 years ago and people buried 10,000 years ago in the region of Lagoa Santa and Pedro Leopoldo (MG) — the quick journey would have allowed this type of population diffusion.
“But as I will always say for every question you ask me, we need more data,” joked the author in an interview with sheet by videoconferencing. “In the case of North America, for example, we have almost no DNA from ancient skeletons this age — I’m working on it, by the way!”
It is at this point, however, that the mysteries begin. Several South American indigenous populations also carry, in their DNA, modest signs of the ancestral contribution of enigmatic groups designated as “population Y”—from the Tupi term “Ypikuéra,” or “ancestor.”
The genomic marks of population Y reveal a distant but significant kinship with peoples of the Pacific whose appearance is quite different from that of present-day indigenous people, such as the Australian Aboriginals and the Natives of New Guinea.
“This could be an indication of the presence of this population on the American continent before the Last Glacial Maximum, which would be fascinating. Or it could be linked to different subpopulations within Beringia, one of which would correspond to this heritage of population Y, which also seems plausible. At the moment, I don’t have a preferred hypothesis in this regard, because I don’t do this type of population modeling. I’m a bench scientist”, says the American researcher.
“I’m trying to keep an open mind because I think our field has suffered a lot from this thing of holding on to preconceived ideas.”
Even more intriguing is the fact that the skulls of the ancient inhabitants of Lagoa Santa, the most important Brazilian archaeological site when it comes to understanding the population of the continent, have shapes that resemble those of the aborigines of the Pacific, as shown in classic works by bioanthropologist Walter Neves. , from USP.
However, DNA tests showed that there is no correlation between the presence of the genes of population Y and the shape of the skulls. “Perhaps these are characteristics that are linked to ancestry at the local level, but to me it seems that cranial morphology is not going to help us resolve these issues.”
The researcher’s book also stands out among the works that approach this area of ​​research for frankly confronting the legacy of colonialism and racial prejudice that surrounds the study of indigenous prehistory since the 18th century. Raff argues that it is necessary to take into account the relationship of current native peoples with their ancestors before any genomic studies with ancient skeletons.
In fact, several DNA studies have revealed that, even when there are temporal distances of several thousand years, it is common for a prehistoric individual to be related to the indigenous people who still live in the region where he was buried. In such cases, it is legitimate for current ethnic groups to ask for the repatriation of the mortal remains and a new burial, she says, even if it is no longer possible to study that individual in the future.
What about genomic studies on things like human behavior or intelligence involving indigenous peoples? Is there a way to carry out this type of work without falling into ethical problems or reinforcing racial stereotypes? “I think research like this would have to start from the needs of these people, and with a tremendous ethical framework to prevent abuse,” she says. “It’s not the kind of thing I would do. I don’t think we should ban this kind of research, but you have to be very careful.”
Origin: A Genetic History of the Americas
author Jennifer Raff
Publishing company Twelve
How much BRL 55.67 (ebook); 369 pages
