28 September 2019 | New Scientist | 37began to doubt its existence. Then, last year,
came the discovery that a person who died
in eastern Brazil 10,400 years ago carried
the Australasian-like DNA. The individual
belonged to the Ancestral A line of Native
Americans that we know came to occupy South
America. Given that Population Y DNA hasn’t
been found in Ancestral A remains in North
America, the geneticists suggest the two
groups met and interbred after they arrived
in South America. They say this might indicate
that Population Y Beringians were the very
first people to push into South America. If so,
the inhabitants of early sites there – such as
the 14,200-year-old Monte Verde in Chile – left
a genetic legacy we now see only in some
Amazonian people. It is an idea that chimes
with a growing realisation that the peopling
of South America was more complicated than
previously thought.
Some 15,000 years ago, a small band of
Beringians stood on the threshold of a new
world. In time, their descendants would create
giant artworks in the Nazca desert of Peru,
begin humanity’s love affair with chocolate
in the forests of Ecuador, and build great
civilisations in Mexico. Today’s Native
American populations still carry the genetic
legacy of those remarkable frontiersfolk. ❚One interpretation is that, about 9000 years
ago, their ancestors mingled with a mysterious
group, provisionally dubbed UPopA, which
seems to be another subpopulation originating
in Beringia some 25,000 years ago.
Then there is the enigmatic Population Y.
In 2015, geneticists announced that some
members of the Suruí and Karitiana groups
living in the Amazon share a curious
genetic connection with some Indigenous
Australasians. The simplest explanation
is that this originated in a prehistoric east
Asian group, Population Y, which was ancestral
to the first Australasians and also contributed
genetic material to the New World via Beringia.
However, geneticists have found no signs of
Population Y in ancient DNA from Beringians
or North Americans, and some researchersColin Barras is a writer based
in Ann Arbor, Michiganvariants may have been naturally selected in
the Native American founder population while
it was isolated in Beringia, says Hünemeier.
All this research is building a picture of life
on the American frontier. But until recently,
the Beringian incubation was generally viewed
as little more than a curious prologue to the
story of the first Americans. This held that the
real epic began about 15,000 years ago when
the ice sheets retreated and a small, genetically
homogeneous population moved from
Beringia into the New World.
American adventure
By 14,600 years ago, the founding population
had split into two distinct Native American
subpopulations. One, the Ancestral B group,
apparently stuck largely to the very north of
North America, where many of its descendants
still live today. The second, the Ancestral A
group, gave rise to a famous North American
prehistoric culture, the Clovis, and also spread
south into Central and South America over
the next couple of millennia. Or that’s what
we thought. But within the past year, we have
learned that the Beringian people fractured
into subpopulations during the incubation
period. This means that several genetically
distinct groups moved into the New World.
The clearest evidence for this comes from
DNA locked in the bones of two children who
were buried in Alaska, 11,500 and 9000 years
ago. Both belong to a genetic group – the
Ancient Beringians – that split from the rest
of the Beringians about 22,000 years ago.
The idea that this happened in Beringia and the
two subpopulations then avoided mixing for
thousands of years isn’t as implausible as it
might seem. Malhi points out that tree species
in Beringia went through a similar population
fragmentation during the Last Glacial
Maximum. Perhaps populations became
isolated because each adapted to a unique
microclimate within the area, he suggests.
At present, there is no evidence that
the Ancient Beringians made much of a
contribution to the peopling of the New
World. Even after the ice sheets retreated, they
seem to have lingered in the Beringia region,
eventually vanishing when populations of
Native Americans from further south pushed
back north into Alaska. However, this may not
have been the only subpopulation to branch
off during the Beringian incubation. And
others might have had a greater wanderlust.
Last year, researchers reported that the
Mixe people of Mexico carry a genetic
signature unlike that of their neighbours.
Genes that helped
people survive in
the subarctic can still
be found in Native
Americans todayExtraordinary
human remains
have been found
near the Yana
river in SiberiaPA
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