New
genetic study seeks
the first Central Americans
By the A.M. Newspapers
News Service
Who were the original Central Americans?
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 July 11 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 Central Aemrica'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, among them the
Miskito.
The question of the country's first residents also will be a topic in
Costa Rica Nov. 14 to 16 when the Asociación
Latinoamericana de Antropología Biológica holds its 12th
congress in the Central Valley. 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.
