Washington, July 24
Debunking the latest
discovery claiming that the first people to reach the Americas came from
Siberia, now in Russia, around 23,000 years ago, new research proposes
that native Americans living in the Amazon bear an unexpected genetic
connection to indigenous people in Australasia.
The new discovery suggests a previously unknown wave of migration to the Americas thousands of years ago.
"There
is a strong working model in archaeology and genetics that most Native
Americans today extend from a single pulse of expansion south of the ice
sheets - and that is wrong. We missed something very important in the
original data,†claimed David Reich, professor of genetics at Harvard
Medical School and senior author of the study.
Previous research
showed that native Americans from the Arctic to the southern tip of
South America can trace their ancestry to a single "founding population"
called the First Americans.
In 2012, Reich and colleagues
enriched this history by showing that certain indigenous groups in
northern Canada inherited DNA from at least two subsequent waves of
migration.
The new study, published in the journal Nature, indicates that there is more to the story.
Pontus
Skoglund, first author of the paper and a postdoctoral researcher in
the Reich lab, was studying genetic data when he noticed a strange
similarity between one or two Native American groups in Brazil and
indigenous groups in Australia, New Guinea and the Andaman Islands.
"That was an unexpected and somewhat confusing result,†said Reich.
The team analysed publicly available genetic information from 21 native American populations from Central and South America.
They also collected and analysed DNA from nine additional populations in Brazil.
The team then compared those genomes to the genomes of people from about 200 non-American populations.
The link persisted.
The
Tupi-speaking Surui and Karitiana and the Ge-speaking Xavante of the
Amazon had a genetic ancestor more closely related to indigenous
Australasians than to any other present-day population.
The researchers believe the ancestry is much older - perhaps as old as the First Americans.
"We
have done a lot of sampling in East Asia and nobody looks like this. It
is an unknown group that doesn't exist anymore,†Skoglund emphasised.
The team has named the mysterious ancestor Population Y.
The
team proposes that Population Y and First Americans came down from the
ice sheets to become the two founding populations of the Americas.
"We do not know the order, the time separation or the geographical patterns,†Skoglund concluded.
To answer this, researchers need to sample DNA from the remains of a person who belonged to Population Y.
Such DNA has not been obtained yet.
One
place to look might be in the skeletons of early Native Americans whose
skulls some researchers say have Australasian features.
"We have
a broad view of the deep origins of Native American ancestry, but
within that diversity we know very little about the history of how those
populations relate to each other," Reich concluded.
