When Dr. Juan Aviles went to school in Puerto Rico, teachers taught him that the original people of the island, the Taino, vanished soon after Spain colonized it. But his grandmother told him that they were descended from Taino ancestors. "I didn't trust her initially," the physician said.

But research has led Aviles to recognize that his grandmother was onto something. A study in the journal Nature, for example, shows that, on average, about 14% of people's ancestry in Puerto Rico can be traced back to the Taino, 4% in Cuba and 6% the Dominican Republic.

DNA found in ancient skeletons shows the islands were populated in two distinct waves. But those living there before colonial contact were not extinguished; millions of people living today inherited their DNA, along with traces of their traditions and languages.

The first residents appear to have lived mostly as hunter-gatherers, catching game and fish while maintaining small gardens. Starting in the early 2000s, geneticists managed to obtain a few bits of preserved DNA of the ancient people. Advances have made it possible to pull entire genomes. "We went from zero full genomes two years ago to over 200 now," said Maria Nieves-Colón, an anthropological geneticist at the University of Minnesota who was an author of a different large-scale genetic study.

The genes of the oldest known residents of the Caribbean link them with the earliest populations that settled in Central and South America. "It's a very distinctive, deep lineage," said David Reich, an author of the study and a geneticist at Harvard Medical School.

But it's not yet clear from where on the mainland the early Indigenous Americans set sail in dugout canoes to reach the Caribbean islands.

About 2,500 years ago, the archaeological record shows, people started living in bigger settlements, intensively farming and creating more sophisticated pottery. For archaeologists, the change indicates the end of what they call the Archaic Age and the start of a Ceramic Age.

Nieves-Colón and other researchers have found that the islanders' DNA also shifted with a new genetic signature. Their DNA links them to small tribes still living today in Colombia and Venezuela.