The largest study of ancient human DNA in America provides a clearer view of the history of the original Caribbean islands, when combined 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 large migratory waves in the Caribbean by two different groups, thousands of years apart, revealing a archipelago populated by very mobile people, with distant relatives who often live on different islands.
Reich’s lab has also developed a new genetic technique for estimating population size in the past, showing that the number of people living in the Caribbean when Europeans arrived was much lower than previously thought, probably by dozens. thousands, instead of 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 help resolve long-running debates, confirm hypotheses, and highlight remaining mysteries.
This “dramatically advances our understanding of the Caribbean in one fell swoop,” says Keegan, curator of the Florida Museum of Natural History and co-author of the study. “The methods developed by David’s team helped to solve some questions that he didn’t even know. which 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 shed new light on the movement of animals and humans, especially in the Caribbean, where each island can be a unique microcosm of life.
While tropical heat and humidity can quickly break down organic matter, the human body contains a strong box of genetic material – a small, unusually dense part of the bone that protects the inner ear.
Using this structure in the first place, 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 academics from the Caribbean, received permission to perform genetic analysis from local governments and cultural institutions that acted as caregivers of human remains. The authors also engaged representatives of indigenous Caribbean 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 instrument users, sailed to Cuba about 6,000 years ago, gradually expanding eastward to other islands during the region’s Archaic Age.
It is not clear where they come from: although they are more closely related to Central and South America than to North America, their genetics do not match any particular indigenous group. However, similar artifacts found in Belize and Cuba may suggest a Central American origin, Keegan notes.
Between 2,500 and 3,000 years ago, farmers and potters associated with Arawak speakers in northeastern South America established a second route to the Caribbean. Using the fingers of the South American Orinoco River Basin as highways, they traveled inland to the coast of Venezuela and advanced north to the Caribbean Sea, establishing Puerto Rico and eventually moving west. Their arrival gave birth to the region’s pottery era, marked by agriculture and the widespread production and use of pottery.
Over time, almost all genetic traces of people in the Archaic Age have disappeared, except for a resistance community in western Cuba that persisted until the arrival of the Europeans. Mixed marriages between the two groups were rare and only three people in the study showed mixed ancestry.
Many Cubans, Dominicans and Puerto Ricans are today descendants of pottery people, as well as enslaved European and African immigrants. But researchers have analyzed only marginal evidence of the ancestors of the archaic age in modern individuals. “This is a great mystery,” Keegan said. “It’s especially curious for Cuba that we don’t see more archaic ancestors.”
In the Age of Ceramics, Caribbean pottery has undergone at least five significant style changes in 2000 years. The ornate red pottery, decorated with white-painted designs, gave rise to simple beige vessels, while other vessels were sprinkled with small dots and incisions or had carved animal faces that probably doubled as handles.
Some archaeologists have indicated these transitions as evidence of new migrations to the islands. But DNA tells another 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 be inspired by aliens.
“This was a question we might not have asked if we didn’t have an archeology expert on our team,” admits co-author Kendra Sirak, a postdoctoral fellow in the Reich lab. “We document this remarkable genetic continuity throughout the changes in the style of ceramics. We are talking about “ships against people” and, as far as we know, these are just ships. “
Highlighting the region’s interconnectivity, a study of male X chromosomes found 19 pairs of “genetic cousins” living on different islands, people who share the same amount of DNA as biological cousins, but can be separated by generations.
The discovery of such a large proportion of genetic cousins in a sample of less than 100 men is another indicator that the total population size in the region was small, says Reich, professor of genetics at the Blavatnik Institute of HMS and professor of biology. evolutionary. human at Harvard. “When you sample two modern individuals, you often don’t find them close relatives,” he said. “Here, we find relatives everywhere.”
A technique developed by the study’s co-author, Harald Ringbauer, a postdoctoral fellow in the Reich Laboratory, used common DNA segments to estimate the size of the previous population, a method that could be applied to future studies of ancient people.
The Ringbauer technique showed that between 10,000 and 50,000 people lived on two of the largest islands in the Caribbean, Española and Puerto Rico, shortly before the arrival of Europeans. This is well below the million inhabitants described by Columbus, Keegan notes.
Later, 16th-century historian Bartolomé de las Casas claimed that the region was home to 3 million people before it was decimated by European slavery and disease. Although this was 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 the number was not 1 million or millions of people, but tens of thousands, does not make the erasure less significant,” he says.