Although for many this may seem like a trivial question, there are academics who are devoting their lives to answer this puzzle.
The results of an extensive genetic study published Wednesday cites the accepted belief that the Americas were populated by Asians who came across an Arctic land bridge 15,000 years ago when the oceans were lower and much of the water was locked up in ice.
The study cites three migrations, but the last two were smaller and those who participated did not make the trip far south, according to the genetic evidence, said the study.
Lead institutions in the study published Wednesday were University College London and Harvard University Medical School. Participating was Ramiro Barrantes Mesén, a professor and vice rector at the University of Costa Rica who has been studying population migrations for years.
A curious aspect of the findings is that Costa Rica’s first settlers appear to have continued on into South America and then backtracked.
“. . . Central American Chibchan-speakers have ancestry from both North and South America, reflecting back-migration from South America and mixture of two widely separated strands of native ancestry,” said a summary of the study.
According to earlier work by Barrantes, the native groups in Costa Rica all appear to be related by blood as well as linguistically and broke off into separate groups starting about 7,000 years ago.
“For years it has been contentious whether the settlement of the Americas occurred by means of a single or multiple migrations from Siberia,” said Andres Ruiz-Linares, a University College London professor who coordinated the study. “But our research settles this debate: Native Americans do not stem from a single migration. Our study also begins to cast light on patterns of human dispersal within the Americas.” He was quoted in a news release.
In the most comprehensive survey of genetic diversity in Native Americans so far, the team took data from 52 Native American and 17 Siberian groups, studying more than 300,000 specific DNA sequence variations called single nucleotide polymorphisms to examine patterns of genetic similarities and differences between the population groups, said the release from the London university’s news service.
What the researchers looked for were slight differences in the way an individual’s DNA was constructed. The groups that make up Costa Rica’s native populations today seem to be very similar in their DNA variations. The Chibcha language, which is now extinct, was typical of native peoples from northern Colombia to Honduras.
Included are Costa Rican native groups now known as BriBir, Cabécar, Borũca, Teribe and Guaymi. There are other groups in Panamá and north in Nicaragua and Honduras.
The question of the country’s first residents also will be a topic in the Central Valley Nov. 14 to 16 when the Asociación Latinoamericana de Antropología Biológica holds its 12th congress. Academics from all over Latin American and from the United States are expected to attend.
“There are at least three deep lineages in Native American populations,” said co-author David Reich, professor of genetics at Harvard Medical School, according to the summary of the most recent study. “The Asian lineage leading to First Americans is the most anciently diverged, whereas the Asian lineages that contributed some of the DNA to Eskimo-Aleut speakers and the Na-Dene-speaking Chipewyan from Canada are more closely related to present-day East Asian populations.”
The team also found that once in the Americas, people expanded southward along a route that hugged the coast with populations splitting off along the way. After divergence, there was little gene flow among Native American groups, especially in South America.
The research team also said that it was successful in devising ways to overlook the genetic contributions made by Europeans and Africans who arrived in the Americas after 1492.
They also said they discovered that some North Americans traveled to Asia and left evidence of their DNA there.
Although Ruiz-Linares expresses certainty in his study results, there are other scientists who claim that modern man was in the Americas at least 50,000 years ago. Other reputable scientists suggest that South America was settled by immigrant who came by boat from the Pacific.