DNA AMA

Genetics reveal a new truth about ancient Caribbean peoples

"We can consider them the first," a researcher tells Inverse.

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World history has often been filtered through a very Euro-centric bent. Textbooks have too often ignored or downplayed the rich history of the Americas prior to European contact.

But new research published in the journal Nature focuses on these little-understood groups of pre-contact people, reshaping our understanding of indigenous ancestry and the formation of an ancient civilization in the Caribbean.

What they found — The study concerns the genetic origins of peoples that migrated to the Caribbean at two different times: the Archaic and Ceramic ages. The researchers studied the DNA of 174 different ancient individuals using radiocarbon dating and genome analysis.

Kendra Sirak, a lead co-author on the study and postdoctoral fellow at Harvard Medical School, tells Inverse her team confirmed these are ancient people were first to arrive.

"These archaic people — we can consider them the first people to move into the Caribbean," Sirak says.

The Archaic people predominantly used stone tools, which is how archaeologists can easily identify them. The study records evidence of a 3,100-year-old individual from the Archaic era, but humans likely first settled in the Caribbean around 6,000 years ago.

Sirak says that these Archaic people likely moved to the Caribbean from Central and South America, which the researchers determined through genetic comparisons with modern-day indigenous people in the Americas.

"We see that these people share more genetic similarity with presently people who live in Central and South America than they do with people who live in say Mesoamerica or North America," Sirak says.

But around 2,300-2,500 years ago, the region begins transitioning into the Ceramic period, which we associate with the use of ceramics — like pottery.

Pottery displayed at a roadside stand, Barbados. Ceramics were central to the researchers' analysis of ancient people.Glowimages

At this point, a new group with a different genetic history migrated to the Caribbean, and that group became associated with the use of ceramics, possibly indicating the development of complex civilizations.

"When we see ceramic use come into the Caribbean, we also see things like intensified agriculture. And because of that, we see an increase in population sizes," Sirak says.

Like they did with the Archaic people, Sirak and her team compared the Ceramic people's DNA to the genetics of modern-day populations in order to determine their geographic origins, which they traced to the northeastern part of South America.

"We determined that they shared the most similarity to people who live in present-day Venezuela and the Guianas and who speak languages in the Arawak language family," Sirak says. "This is consistent with the presence of Arawak languages in the Caribbean at the time of European contact."

Sirak adds, "It suggests that this region is the most likely source for the Ceramic Age movement into the Caribbean."

Remarkably, the study challenges previous research in this area, which traced the origins of some ancient peoples in the Caribbean to North America. But researchers in this study found little support for the North American hypothesis.

A figure from the study charting the arrival of ancient peoples.

Digging into the details — The genetic survey allowed the researchers to conclude that the ancient Ceramic peoples across a wide swathe of the Caribbean — spanning from the Bahamas to Puerto Rico — had a lot of genetic history in common.

Researchers could, therefore, see a stark genetic difference between the Archaic people and the Ceramic people that followed them.

"In the ceramic-using Caribbean, they all share more genetic similarity with each other than they do with any stone tool users," Sirak says.

Geneticists also collaborated with prominent archaeologists in the study to research ancient pottery, which helped them better understand the evolution of the Ceramic people in the Caribbean.

"Our work shows that is that it is likely that new pottery styles were developed and spread within the Caribbean by the people who lived in this region," says Sirak. "It is less likely that multiple waves of people moving from the American continents were responsible for the observed changes in ceramic style."

Researchers were also able to compare pottery from the Caribbean to the ceramics from the Arawak people, further supporting their theory of migration from South America.

"There's also some archaeological connections between Caribbean styles of pottery and Arawak styles," Sirak says.

Modern Implications — By comparing ancient peoples to modern indigenous groups, researchers were able to find shared genetic ancestry between both groups, conclusively linking the past to the present through their DNA.

"Present-day people of the Caribbean have ancestry from three main groups—pre-contact Indigenous American people, immigrant Europeans, and Africans who were brought to this region as part of the slave trade," says Sirak.

Sirak adds, "Importantly, our work shows that the Indigenous ancestry found in present-day Caribbean people can be directly traced to pre-contact times."

From the study - A genetic representation of ancient peoples across the Caribbean.

Why it matters — This finding upends prior research on how people migrated to the Caribbean.

"Unlike some people have argued, it did not solely result from post-contact movements of Indigenous people from the American continents mediated by Europeans," Sirak says.

The European conquest of the Americas had a catastrophic impact on the survival of these ancient civilizations and cultures, but the research of Sirak's team suggests that there was a rich and vibrant civilization prior to European contact.

"What this work shows is that these people were advanced, and they were dynamic, and they were creative and they were connected, Sirak says. "It's a new, new lens into this thriving, flourishing, really dynamic society.

What's next — Sirak also believes that their work can provide genetic support to the ancestral claims of indigenous people living today, who continue many of the cultural practices of their forebearers.

"Many people in the Caribbean feel a biological or cultural ancestry to the people who lived on these islands thousands of years ago- and while genetics alone does not determine identity, our work shows that the genetic legacy of the pre-contact people of the Caribbean lives on in people of the region today."

Abstract: Humans settled the Caribbean about 6,000 years ago, and ceramic use and intensified agriculture mark a shift from the Archaic to the Ceramic Age at around 2,500 years ago. Here we report genome-wide data from 174 ancient individuals from The Bahamas, Haiti and the Dominican Republic (collectively, Hispaniola), Puerto Rico, Curaçao and Venezuela, which we co-analysed with 89 previously published ancient individuals. Stone-tool-using Caribbean people, who first entered the Caribbean during the Archaic Age, derive from a deeply divergent population that is closest to Central and northern South Americans; contrary to previous work, we find no support for ancestry contributed by a population related to North Americans. Archaic-related lineages were >98% replaced by a genetically homogeneous ceramic-using population, related to speakers of languages in the Arawak family from northeast South America, who moved through the Lesser Antilles and into the Greater Antilles at least 1,700 years ago, introducing ancestry that is still present. Ancient Caribbean people avoided close kin unions despite limited mate pools that reflect small effective population sizes, which we estimate to be a minimum of 500–1,500 and a maximum of 1,530–8,150 individuals on the combined islands of Puerto Rico and Hispaniola in the dozens of generations before the individuals who we analysed lived. Census sizes are unlikely to be more than tenfold larger than effective population sizes, so previous pan-Caribbean estimates of hundreds of thousands of people living are too large. Confirming a small and interconnected Ceramic Age population, we detect 19 pairs of cross-island cousins, close relatives around 75 km apart in Hispaniola and low genetic differentiation across islands. Genetic continuity across transitions in pottery styles reveals that cultural changes during the Ceramic Age were not driven by migration of genetically differentiated groups from the mainland, but instead reflected interactions within an interconnected Caribbean world.
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