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disagreement about where exactly this period
of isolation happened.
Potter is convinced that the ancestors of
today’s Native Americans did, in fact, retreat
south as conditions worsened, and spent the
Last Glacial Maximum near Lake Baikal at
approximately 53° north. We even have DNA
from a boy who died there 24,000 years ago.
Like the Yana children, he was related, although
not directly ancestral, to the Native American
founding population. But other researchers,
including Hoffecker, are convinced that the
incubation occurred in Beringia itself. The
region’s geographical remoteness makes it a
more likely place for a population to be isolated
for millennia, they argue. Indeed, there is
genetic evidence that this happened to other
mammals – including elk and brown bears –
during the Last Glacial Maximum.
Another clue comes from linguistics. There
are similarities between some of the languages
spoken in the Americas and Ket – a Yeniseian
language spoken in Siberia to the west of Lake
Baikal. A language family tree indicates that
the oldest representatives of this group were
spoken near the Beringian region, suggesting
this is where it arose. Ket speakers may be
descendants of Beringians who migrated back
into Siberia after the Last Glacial Maximum.
Hoffecker points to more reasons why an
extended stay in Beringia makes sense. As
Earth’s climate cooled and ice sheets began to
form, global sea levels dropped dramatically.
By 28,000 years ago, the seas may have been
100 metres lower than they are today. As a
result, thousands of square kilometres of new
land appeared in south-central Beringia. And
not just any old land. Although most of the
subarctic became cold and arid after 30,000
years ago, climate models and pollen records
indicate that this region was humid and mild,
perhaps because Pacific currents pushed warm
air over it. “There’s no other place on Earth
where you got this significant expansion
of viable habitat during the peak of the Last
Glacial Maximum,” says Hoffecker.
Considering Beringia’s size and its benign
climate, one estimate suggests that tens of
thousands of people could have lived there
during the peak of the Last Glacial Maximum.
There would have been big challenges.
During winter, anyone living today above
46° north will struggle to get the sunlight they
need to trigger vitamin D synthesis in the skin.
“Even if you’re naked outside, you’re not going
to get enough ultraviolet light exposure,” says
Leslea Hlusko at the University of California,
Berkeley. Adults can largely overcome this
problem by eating vitamin D-rich foods suchThe discovery rewriting human history
Hear Lee Berger speak at New Scientist Live
newscientistlive.com“ These people
could have been
cut off from the
rest of humanity
for 15,000 years”
The pioneers of a new world
Hardy subarctic people lived near the Yana river some 32,000 years ago. It was at the edge of an area known as Beringia,
which included dry land between what is now Siberia and Alaska. Then Earth began to cool and ice spread, trapping
people in this habitable oasis. Isolated from the rest of humanity, Beringians developed distinct genetic variants that can
help track how populations of them moved into the Americas 15,000 years agoLAKE
BAIKALPACIFIC OCEANPopulation Y?Ancestral BAncestral AUPopAAncestors of Mexico’s
Mixe people interbreed
with UPopAYana site32,000
years agoDry land during Last
BERINGIA Glacial MaximumAncient BeringiansPossible area
of isolation
24,000-15,000 ya9000 yaMonte Verde14,200 yaPopulation Y and
Ancestral A people may
have interbredArctic circle45°55°10,400 ya11,500 yavariant also leaves people with strikingly thick
enamel on the tongue side of their incisors.
So she, Hoffecker and their colleagues looked
at the global distribution of these curious
teeth. They are all-but absent in most regions,
present to some degree in east Asia – and
almost ubiquitous among current and past
Native American populations. To Hlusko,
this fits with the idea that the ancestors
of Native Americans, isolated in Beringia,
evolved the EDAR variant, which helped them
overcome their vitamin D problem and gave
them thicker tooth enamel as a side effect.
“It’s a great hypothesis,” says Tábita
Hünemeier at the University of São Paulo,
Brazil. She also thinks the Native American
founder population was isolated in Beringia –
and that it evolved in response. In 2017,
Hünemeier and her colleagues discovered
that people in many present-day Native
American populations carry unusual
versions of a family of genes called FADS genes.
People with these variants are better able to
process the protein and fatty acid-rich diet that
subarctic communities typically consume. Theas oily fish, but nursing infants would be at risk
of vitamin D deficiency, which can weaken the
immune system and cause skeletal problems,
among other things. She thinks evolution
found a solution.
One variant of a gene called EDAR changes
the density of milk ducts within the female
breast. Hlusko suspects that this boosts the
transfer of nutrients, including vitamin D,
from mothers to their infants. The same EDAR