A Pacific mystery in Rio
In the collection of Brazil's National Museum in Rio de Janeiro, among remains of the indigenous Botocudo people, lies a puzzle that challenges the history of the Americas. Genetic analysis of some of these skulls revealed mitochondrial DNA (mtDNA) haplogroups typically found in Polynesia. A 2013 study led by geneticist Sergio Pena analyzed 14 Botocudo skulls and found that two of them contained Polynesian genetic markers. Subsequent whole-genome sequencing confirmed the result for two individuals, designated Bot15 and Bot17. Their genomes were almost entirely Polynesian, with no detectable Native American ancestry.
The Botocudo were hunter-gatherers from Brazil's interior, in what is now Minas Gerais and Espírito Santo. The name, a pejorative from the Portuguese word "botoque," refers to the large wooden discs they wore in their lips and earlobes. After contact with Europeans beginning in the 16th century, they were systematically exterminated, and by the late 19th century, their population was devastated. The skulls in the museum collection largely date to this period. Radiocarbon dating on the two Polynesian-linked skulls places their deaths before the 19th century, with one dating as early as the 15th century. This timeline makes it harder to explain how individuals with purely Polynesian DNA came to be in the interior of Brazil.
Competing explanations
Three main scenarios attempt to explain the anomalous DNA. The most direct, though unsubstantiated, is pre-Columbian trans-Pacific contact. Polynesian navigators were among the greatest seafarers in history, settling remote islands like Easter Island between 1200 and 1300 AD. While they possessed the capability for long-distance voyages, finding evidence of a journey to Brazil, thousands of kilometers across a continent from the Pacific coast, is difficult.
A second hypothesis involves European-mediated transport after 1500. Polynesians could have been brought to Brazil on European ships as crew, or more grimly, through the slave trade. A known slave trade existed between Peru and Polynesia, but this is unlikely to be the source. Another possibility is the Madagascar-Brazil slave trade, but the genetic signatures do not match the populations of Madagascar, who are of Southeast Asian, not Polynesian, origin.
A third model, proposed by anthropologist Walter Neves, connects the Botocudo to a broader "Paleoamerican" population. This theory suggests that the first wave of migrants to the Americas, including the 11,500-year-old "Luzia" skeleton also found in Brazil, had a distinct skull morphology (long and narrow) different from most later Native Americans. Some Botocudo skulls share these traits, suggesting they could be a relict population of these first migrants. The genetic link to Polynesians under this model would stem from a very ancient, shared ancestry in Asia, not from direct contact across the Pacific. The purely Polynesian nature of the two genomes, without any Native American admixture, complicates all of these theories.