The largest study of ancient human DNA in the Americas offers a sharper focus on the history of the original Caribbean islanders, combining it with decades of archaeological work.
According to an international team of researchers, led by David Reich of Harvard Medical School, in the journal Nature, genetics traces two major waves of migration to the Caribbean by two different groups, thousands of years apart. revealing an archipelago populated by very mobile people, with distant relatives who often live on different islands.
Reich’s lab also developed a new genetic technique to estimate 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 in the tens. of thousands, instead of the million or more reported by Christopher Columbus and his successors.
For archaeologist William Keegan, the work in the Caribbean spans more than 40 years, ancient DNA offers a powerful new tool to help resolve long-standing debates, confirm hypotheses, and highlight remaining mysteries.
This “dramatically advances our understanding of the Caribbean in one fell swoop,” said Keegan, curator of the Florida Museum of Natural History and lead co-author of the study. helping to address questions we didn’t even know 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, particularly 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 safe of genetic material: a small and unusually dense part of the bone that protects the inner ear.
Using primarily 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, received permission to conduct genetic analysis of local governments and cultural institutions that acted as caregivers of human remains. The authors also involved representatives of indigenous communities in the Caribbean 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, gradually expanding eastward to other islands during the region’s Archaic Age.
It is unclear where they come from: although they are more closely related to Central Americans and South Americans than to Americans, their genetics do not match any particular Native American group. However, similar artifacts found in Belize and Cuba may suggest a Central American origin, Keegan points out.
Between 2,500 and 3,000 years ago, farmers and potters related to the Arawak speakers of northeastern South America established a second path to the Caribbean. Using the fingers of the Orinoco River basin of South America as roads, they traveled from the interior to the coast of Venezuela and advanced north toward the Caribbean Sea, establishing Puerto Rico and finally moving toward to the west. His arrival marked the beginning of the Ceramic Age of the region, marked by agriculture and the widespread production and use of pottery.
Over time, almost all genetic traces of people in the Archaic Age disappeared, except for a resistance community in western Cuba that persisted until the arrival of Europeans. Mixed marriages between the two groups were uncommon, and only three individuals in the study showed mixed ancestry.
Many Cubans, Dominicans, and Puerto Ricans today are descendants of people of the Pottery Age, as well as enslaved European and African immigrants. But researchers observed only marginal evidence of the ancestry of the Archaic Age in modern individuals. “This is a great mystery,” Keegan said. “It is especially curious for Cuba that we do not see more archaic ancestry.”
During the Ceramics Era, Caribbean pottery underwent at least five marked changes in style over 2000 years. The ornate red pottery decorated with white-painted designs gave way to simple beige vessels, while other pots were dotted with small dots and incisions or had sculpted animal faces that probably bent like 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 and been inspired by strangers.
“This was a question we might not have been able to ask if we hadn’t had an archeology expert on our team,” said lead co-author Kendra Sirak, a postdoctoral fellow in the Reich lab. “We document this remarkable genetic continuity through changes in the style of pottery. We talk about ‘containers against people’ and, as far as we know, they are just containers. “
Highlighting the interconnectivity of the region, 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.
Discovering such a high proportion of genetic cousins in a sample of less than 100 men is another indicator that the size of the total population in the region was small, highlights Reich, professor of genetics at HMS Blavatnik Institute and professor of human evolutionary biology at Harvard. “When samples are taken from two modern individuals, it is not uncommon to find them to be close relatives,” he said. “Here, we’re finding relatives everywhere.”
A technique developed by study co-author Harald Ringbauer, a postdoctoral fellow in the Reich lab, used shared segments of DNA to estimate past population size, a method that could also be applied to future human studies. old.
The Ringbauer technique showed that between 10,000 and 50,000 people lived on two of the largest islands in the Caribbean, Spain and Puerto Rico shortly before the arrival of Europeans. That’s well below the million inhabitants Columbus described, Keegan points out.
Later, 16th-century historian Bartholomew of the Houses claimed that the region had housed 3 million people before being decimated by European slavery and disease. 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 the number was not 1 million or millions of people, but tens of thousands, does not make this erasure less significant,” he says.