28 September 2019 | New Scientist | 35dishes that perhaps served ritual purposes.
There were human remains at the site as
well – two tooth fragments – and we learned
this year that both contain preserved ancient
DNA. The teeth belonged to children who
were part of a population related to, although
not directly ancestral to, modern Native
Americans. But the game-changing discovery
was about the size of the community. These
children were so genetically distinct from
each other that the Yana population may
have numbered more than 500.
It is a startling finding, says Hoffecker.
The Yana site was remote from the southern
centres of human activity in the late Stone
Age, so we might expect the population to
have been tiny, isolated and inbred. “But it’s
a fairly healthy and robust group,” he says.
This suggests there was a degree of migration
into and out of Beringia, keeping populations
there genetically diverse. But even though
this group may have been flourishing, there
is no good evidence that these people pushed
further east, despite Siberia and the Americas
then being connected by dry land.
There they stayed for generations. Then,
about 30,000 years ago, Earth began to lurch
into a severe cold snap called the Last Glacial
Maximum. Ice sheets grew across North
America, and the route from Beringia to the
New World froze shut. It was some 15,000 years
before conditions began to improve and the
route reopened. The Yana site was abandoned
at the beginning of this period.
However, it seems that other groups stayed
in Beringia. A decade ago, geneticists including
Ripan Malhi at the University of Illinois
discovered subtle genetic differences between
living Native Americans and East Asians
that originated thousands of years before
people entered the Americas. The geneticists
suggested a solution: perhaps the ancestors
of the Native Americans had lived in Beringia,
and become isolated as temperatures dropped
30,000 years ago. Their route south was
blocked by polar deserts in Eurasia and ice
sheets in North America. In theory, these
people could have been cut off from the
rest of humanity for 15,000 years, plenty
of time for random genetic drift to give
them distinctive DNA before they entered
the New World. The idea was labelled the
Beringian incubation or standstill.
Today, most researchers accept that there
was an incubation period, although they now
think it didn’t begin until about 24,000 years
ago, when conditions got really bad, and that it
lasted 9000 years at most. However, there iscovering thousands of square kilometres.
There are disputed signs of human activity
in northern Eurasia 45,000 years ago. But
it is at a 32,000-year-old site in the Arctic
circle that the archaeological record really
begins. On the banks of the Yana river
in Siberia, at the western end of Beringia,
archaeologists have found hundreds of stone
and bone tools, including sewing needles.
The people near the Yana hunted reindeer,
woolly rhinos and birds. Hares were also
caught, perhaps for their pelts, if modern
Arctic peoples are any guide.
Life in Beringia wasn’t unrelentingly grim.
Those inhabiting the Yana site had time for
artistic pursuits: it has yielded dozens of beads
carved from ivory and bone. Archaeologists
also found strips of decorated ivory that may
have been used as hairbands, and shallow ivory >“ The people who
would eventually
conquer the
Americas evolved
some unusual
adaptations
to survive”