The largest study of ancient human DNA in America offers a sharper look at the history of the Caribbean’s original islanders, coupled with decades of archaeological work.
As published in the journal Nature by an international team of researchers led by David Reich, of Harvard Medical School, genetics follows two major waves of migration in the Caribbean through two different groups thousands of years apart, revealing an archipelago which is populated by highly mobile people, with distant relatives often living on different islands.
Reich’s laboratory also developed a new genetic technique in the past to estimate population size, showing that the number of people living in the Caribbean when Europeans arrived was far fewer than previously thought, probably dozens. thousands, rather than the million or more reported by Christopher Columbus and his successors.
For archaeologist William Keegan, whose work in the Caribbean spans more than 40 years, ancient DNA provides a powerful new tool to solve long-standing debates, confirm hypotheses, and highlight remaining mysteries.
This “dramatically improves our understanding of the Caribbean in one fell swoop,” said Keegan, curator of the Florida Museum of Natural History and co-lead author of the study. “The methods David’s team developed helped answer questions he didn’t even know. That we could address.”
Archaeologists often rely on the remains of domestic life (pottery, tools, bone remains and shells) to reconstruct the past. Now, technological advances in the study of ancient DNA are shedding new light on the movement of animals and humans, especially in the Caribbean, where each island can be a unique microcosm of life.
While the heat and humidity of the tropics can quickly break down organic matter, the human body contains a strong box of genetic material – a small, unusually dense bone part that protects the inner ear.
Using this structure, the researchers extracted and analyzed the DNA of 174 people who lived in the Caribbean and Venezuela between 400 and 3,100 years ago, combining the data with 89 previously sequenced individuals.
The team, which includes Caribbean academics, has been granted permission to conduct the genetic analysis of local governments and cultural institutions acting as caretakers of the human remains. The authors also engaged representatives of the Caribbean’s indigenous communities in a discussion of their findings.
Genetic evidence offers new insights into the Caribbean population. The first inhabitants of the islands, a group of stone tool users, sailed to Cuba about 6,000 years ago and gradually expanded east to other islands during the region’s archaic era.
It’s unclear where they come from: although they are more closely related to Central and South Americans than to North Americans, their genetics do not match any particular indigenous group. However, similar artifacts found in Belize and Cuba may point to a Central American origin, Keegan notes.
Between 2,500 and 3,000 years ago, farmers and potters related to the Arawak speakers of northeastern South America laid down a second road to the Caribbean. Using the fingers of the Orinoco River basin in South America as highways, they traveled from inland to the coast of Venezuela and moved north to the Caribbean Sea, settling Puerto Rico and eventually moving west. Their arrival heralded the region’s pottery era, characterized by agriculture and the widespread production and use of pottery.
Over time, almost all the genetic traces of the people of the Archaic era have disappeared, except for a resistance community in western Cuba that survived until the arrival of Europeans. Intermarriage between the two groups was rare and only three people in the study showed mixed ancestry.
Many Cubans, Dominicans, and Puerto Ricans are descendants of Pottery Age people, as well as enslaved European and African immigrants. But the researchers observed only marginal evidence of archaic ancestry in modern individuals. “That is a great mystery – Keegan emphasizes. For Cuba it is especially curious that we no longer see archaic origins.”
During the age of ceramics, Caribbean pottery underwent at least five striking style changes in 2000 years. Ornate red pottery adorned with white-painted designs gave way to simple beige pots, while other pots were studded with small dots and incisions or carved animal faces that likely also served as handles.
Some archaeologists pointed to these transitions as evidence of new migrations to the islands. But DNA tells a different story, suggesting that all styles were developed by descendants of people who came to the Caribbean 2,500-3,000 years ago, although they may have interacted with and were inspired by strangers.
“That was a question we might not have been able to ask had we not had an archeology expert on our team,” admits co-lead author Kendra Sirak, a postdoctoral researcher in Reich’s lab. changes in the style of ceramics. We are talking about ‘vessels against people’ and, as far as we know, they are just vessels. “
Highlighting the region’s interconnectedness, a study of male X chromosomes discovered 19 pairs of “genetic cousins” living on different islands, people who share the same amount of DNA as biological cousins, but who may be separated for generations.
Discovering such a high percentage of genetic cousins in a sample of less than 100 men is another indicator that the region’s overall population size was small, says Reich, a professor of genetics at HMS ‘Blavatnik Institute and a professor of evolutionary biology. human at Harvard. “When you try two modern individuals, you don’t often see them as close relatives,” he said. “Here we find relatives everywhere.”
A technique developed by co-author Harald Ringbauer, a postdoctoral fellow in the Reich Laboratory, used shared segments of DNA to estimate population size in the past, a method that could also be applied to future studies of ancient humans.
Ringbauer’s technique showed that shortly before the arrival of Europeans, between 10,000 and 50,000 people lived on two of the largest islands in the Caribbean, Española and Puerto Rico. This is well below the million residents Columbus described, Keegan notes.
Later, 16th-century historian Bartolomé de las Casas claimed that the region was home to 3 million people before being decimated by slavery and European diseases. While this was also an exaggeration, the number of people who died as a result of colonization remains an atrocity, Reich points out. “This was a systematic program of cultural erasure. The fact that it was not 1 million or millions of people, but tens of thousands, doesn’t make that erasure any less important,” he says.