Opinion | Ancient DNA Is Changing How We Think About the Caribbean

In 1492, Christopher Columbus touched land for the first time in the Americas, reaching the Bahamas, Hispaniola (present-day Dominican Republic and Haiti) and eastern Cuba. After he returned to Spain he reported that he had encountered islands rich in gold. A few years later his brother Bartholomew, who also traveled to the Americas, reported that Hispaniola had a large population whose labor and land could be put to the advantage of the Spanish crown. He estimated the population at 1.1 million people.

Was this figure accurate? It soon was a matter of dispute. Bartolomé de las Casas, a Spanish monk and colonist who became the first chronicler of the human disaster that unfolded in the Americas after the arrival of Europeans, estimated a far larger number: three million to four million.

The population size of “pre-contact” Hispaniola would continue to be a contested issue until the present day, not least because of its profound emotional and moral resonance in light of the destruction of that world. Modern scholars have generally estimated the population at 250,000 to a million people.

Some of the arguments for large population numbers in the pre-contact Americas have been motivated by an attempt to counter a myth, perpetuated by apologists for colonialism like the philosopher John Locke, that the Americas were a vast “vacuum domicilium,” or empty dwelling, populated by a handful of Indigenous groups whose displacement could be readily justified. In a similar vein, some of the arguments for large population sizes have been motivated by a desire to underscore how disastrous the arrival of Europeans was for Indigenous people.

By any measure, the arrival of Europeans was catastrophic for Indigenous Americans. This is true whether the numbers of people were in the hundreds of thousands or millions — or for that matter, the tens of thousands. It is questionable to pin our judgments of human atrocities to a specific number. To learn from the past, it is crucial to be willing to accept new and compelling data when they become available.

In the case of the pre-contact population of Hispaniola, such data have arrived. By analyzing the DNA of ancient Indigenous Caribbean people, a study published in Nature on Wednesday by one of us (Professor Reich) makes clear that the population of Hispaniola was no more than a few tens of thousands of people. Almost all prior estimates have been at least tenfold too large.

This research involved sequencing genetic material taken from skeletal remains. Together with another study of ancient Caribbean DNA published recently by a different lab, scientists now have data concerning the entire genomes of more than 260 people of the ancient Caribbean. (This work was done in collaboration with Caribbean scholars, with permission from Caribbean governments and institutions and in consultation with Caribbean people of Indigenous descent.)

In recent years, researchers studying ancient DNA have accumulated more than 5,000 ancient human genomes (up from none a decade ago), making it possible to use this methodology to ask and answer questions about how past people related to one another and to people living today. The Caribbean is now the first place in the Americas where we have this kind of high-resolution data set for understanding the past, previously available only in Western Eurasia.

The finding about the pre-contact population size in Hispaniola was made possible by a new scientific advance: We are now able to detect “DNA cousins” in ancient genomes — taking two people and determining whether they share large segments of DNA inherited from a recent ancestor. This is similar to what personal ancestry companies like 23andMe and Ancestry do with living people.

When the Reich team applied this method to 91 ancient individuals for whom it had sequenced enough of the genome to carry out this analysis, it found 19 pairs of DNA cousins living on different large islands or island groups in the Caribbean: for example, an individual in Hispaniola with a cousin in the Bahamas, and another individual in Hispaniola with a cousin in Puerto Rico. This meant that the entire population had to be very small; you wouldn’t find that random pairs of people had such a high probability of being closely related if the entire population was large. (To put this in perspective, if you did the same analysis on random pairs of people across China today, DNA cousins would be detected many thousands of times less often.)

The rate of close relationships that the Reich team found is what would be expected for about 3,000 people — at most 8,000 people — in their childbearing years in Hispaniola. The true numbers of people could have been threefold to tenfold larger because at any given time only a fraction of a population is in its childbearing years. Still, we can confidently conclude that the pre-contact population size of Hispaniola was no more than a few tens of thousands of people.

This is a classic ancient DNA surprise — the kind of unexpected finding this new technology has shown repeatedly that it can deliver. For example, the sequencing of a finger bone from Siberia thought to be from a modern human turned out to be from an archaic population not previously known to archaeologists, or even hypothesized by them. Such results emphasize how much we still have to learn about the past.

How should the new findings change the way we think about the fate of Indigenous people in the pre-contact Caribbean? In some ways, not at all. Whatever the starting population, what happened to Indigenous Americans after Europeans arrived amounted to genocide: the systematic obliteration not just of individuals but also of their culture and community — what the philosopher Claudia Card called the “social death” at “the center of genocide.”

Even if you focus more narrowly on statistics, the numbers of deaths in both absolute and relative terms are horrific. According to a 1540 census, the number of Indigenous people in Hispaniola had dropped to 250 people. It dropped to zero in later counts.

In other ways, however, ancient DNA research significantly changes how we think about Indigenous people in the pre-contact Caribbean. Another surprising finding, for instance, is that the genetic legacy of pre-contact Caribbean people did not disappear: They contributed an estimated 14 percent of the DNA of living people from Puerto Rico, 6 percent of that in the Dominican Republic and 4 percent of that in Cuba. In addition, by illuminating the highly mobile lifestyle of pre-contact Caribbean people with many DNA cousins across different islands, the research underscores the degree to which they were connected — a relative unity later fractured by centuries of division into colonial spheres by European powers.

Colonization resulted in such immense destruction that the rich cultures of the pre-contact Caribbean can be reconstructed only through a blend of oral traditions and scientific study, including the new insights provided by ancient DNA analysis. It is a blessing to be able to get closer to this heritage. And it is the loss of the people and cultures that produced this heritage that most provokes our outrage.

David Reich, a professor of genetics and human evolutionary biology at Harvard, is the author of “Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past.” Orlando Patterson, a professor of sociology at Harvard, is the author, most recently, of “The Confounding Island: Jamaica and the Postcolonial Predicament.”

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