A large genetic study has revealed that two distinct groups of humans settled in the Caribbean around 3,000 years apart. According to the Florida Museum of Natural History, the first group was nearly wiped out after the arrival of the second wave of settlers by an unknown cause – possibly warfare or disease.
For the investigation, an international team of researchers led by Harvard Medical School’s Professor David Reich analyzed the genomes of 263 individuals. The study is the most comprehensive analysis of ancient human DNA in the Americas to date.
The experts developed a new genetic technique for estimating past population size. They found that there were far fewer native people in the Caribbean when Europeans arrived than previously thought. The research suggests that this number was likely in the tens of thousands, rather than the million or more described by Columbus.
Study co-senior author William Keegan has studied the history of the Caribbean for more than 40 years. He explained that ancient DNA offers a powerful new tool to help resolve longstanding debates, confirm theories, and explore remaining mysteries.
Keegan said the genetic research “moves our understanding of the Caribbean forward dramatically in one fell swoop,” adding that the methods developed for the current study helped to address questions he didn’t even know could be addressed.
The genetic evidence offers new insights into the settlement of the Caribbean. The islands’ first inhabitants, a group of stone tool-users, boated to Cuba about 6,000 years ago. They gradually expanded eastward to other islands during the region’s Archaic Age.
While the first settlers are more closely related to Central and South Americans than to North Americans, their genetics do not match any particular Indigenous group and their origin is not clear. According to Keegan, similar artifacts were found in Belize and Cuba, indicating a Central American origin.
About 3,000 years later, a group of farmers and potters moved into the Caribbean from South America. After their arrival, the Caribbean transitioned into the Ceramic Age, which was marked by agriculture and widespread pottery production.
Over time, nearly all genetic traces of Archaic Age people vanished, with the exception of one community in western Cuba that persisted as late as the arrival of Europeans. Marriage between the two groups was rare – only three individuals in the study had mixed ancestry.
There is only marginal evidence of Archaic Age ancestry in modern individuals, while many present-day Cubans, Dominicans and Puerto Ricans are the descendants of Ceramic Age people. “That’s a big mystery,” said Keegan. “For Cuba, it’s especially curious that we don’t see more Archaic ancestry.”
A study of male X chromosomes uncovered 19 pairs of “genetic cousins” living on different islands. These pairs represent people who share the same amount of DNA as biological cousins but may be separated by generations. In the most striking example, a man buried in the Bahamas was related to a man buried 600 miles away in the Dominican Republic.
“Showing relationships across different islands is really an amazing step forward,” said Keegan, who added that shifting winds and currents can make passage between islands difficult. “I was really surprised to see these cousin pairings between islands.”
Uncovering such a high proportion of genetic cousins in a sample of fewer than 100 men is another indicator that the region’s total population size was small, said Professor Reich. “When you sample two modern individuals, you don’t often find that they’re close relatives. Here, we’re finding relatives all over the place.”
A technique developed by study co-author Harald Ringbauer used shared segments of DNA to estimate past population size. This technique could also be applied to future studies of ancient people.
Ringbauer’s method revealed that about 10,000 to 50,000 people were living on two of the Caribbean’s largest islands, Hispaniola and Puerto Rico, shortly before European arrival. This falls far short of the million inhabitants Columbus described to his patrons, likely to impress them, said Keegan.
In the 16th century, historian Bartolomé de las Casas claimed the region had been home to 3 million people before being decimated by European enslavement and disease. While this, too, was an exaggeration, the number of people who died as a result of colonization remains an atrocity, said Professor Reich.
“This was a systematic program of cultural erasure. The fact that the number was not 1 million or millions of people, but rather tens of thousands, does not make that erasure any less significant.”
The study is published in the journal Nature.
By Chrissy Sexton, Earth.com Staff Writer