30 January 2021 | New Scientist | 37thousands of stone tools buried between
40,000 and 30,000 years ago that might
have been left by Denisovans – or H. sapiens.
More compelling evidence comes from
Baishiya Karst cave in Xiahe in the north-east
of the Tibetan plateau. It is a sanctuary for
Tibetan Buddhists and, in 1980, a monk
meditating there found a jawbone. “Local
people used to collect bones in this cave
to grind, to make some kind of medicine,”
says Hublin. “Luckily, this monk did not
grind the fossil.” Instead, it was sent to
Lanzhou University in China. It doesn’t
contain any preserved DNA, but, in 2019,
Hublin and his colleagues revealed that
they had managed to extract protein from
one of the teeth. This matched protein found
in Denisovans. They also concluded that the
jawbone was at least 160,000 years old.
Many people found it hard to accept that
Denisovans were living in one of the harshest
environments on Earth 160,000 years ago.
But, in October 2020, researchers led by
Qiaomei Fu at the Institute of Vertebrate
Paleontology and Paleoanthropology in
Beijing, China, reported finding Denisovan
DNA preserved in the sediments of Baishiya
Karst cave. The DNA samples dated from
100,000, 60,000 and possibly also 45,000
years ago. Not only were the Denisovans
there, it looks as if they were there for
at least 115,000 years, plenty of time to
evolve adaptations like the modified EPAS1^
gene. “I was a little more sceptical in the
beginning,” says Viola. But the sediment
DNA sealed the deal. “I’m really convinced.”
That means we now have another
Denisovan specimen, with its own story
to tell. The overall shape of the jawbone
is typical for hominins of the time. Some
features are quite Neanderthal-like, which
Hublin says is to be expected of a sister group.
What marks it as Denisovan are its enormous
teeth. Ongoing excavations at Denisova cave
have yielded three Denisovan teeth, all also
whopping. “The Denisovans are really weird,”
says Shara Bailey at New York University.
Throughout human evolution, teeth have
generally shrunk, but they bucked thathas ever even shown that methyl tags can
“predict” the appearance of a known species.
If the genome cannot tell us what
Denisovans looked like, we must find out
the old-fashioned way – by excavating
Denisovan remains. To that end, people
have been exploring sites in China and
nearby countries, and scouring old
museum collections. For almost a decade,
there was nothing. Now there is.
Bence Viola, a palaeoanthropologist at the
University of Toronto in Canada, has found
several skull fragments in Denisova cave.
Details haven’t been published yet, but
viewing a cast of one over Zoom reveals that
the bone is unusually thick. To Viola, this
suggests that Denisovans were big – perhaps
more than 100 kilograms – with “American
football player body build”. Analysis of their
genome reveals it contains DNA from an
unidentified older population: could they
have interbred with the decidedly bulky
Homo erectus, a species that lived on in
east Asia long enough to have met them?High society
These fragments are the best Denisovan
fossil evidence found so far at the cave, but
archaeologists have expanded the search.
A crucial clue emerged in 2014. Emilia
Huerta-Sánchez now at Brown University in
Providence, Rhode Island, and her colleagues
were studying a gene called EPAS1, which
is involved in the body’s response to low
oxygen levels. People living on the Tibetan
plateau, more than 4 kilometres above
sea level, have a modified version of EPAS1
that helps them cope with the thin air.
Huerta-Sánchez found that this came
from interbreeding with Denisovans
about 43,000 years ago.
Denisova cave is only 700 metres above sea
level, so it seems unlikely that the mutation
arose there. But it would have been a useful
adaptation if Denisovans were living at
high altitude elsewhere. Tentative evidence
of this emerged in 2018. At Nwya Devu on
the Tibetan plateau, a research team found >How far did
Denisovans
roam?We have hard evidence of the
Denisovans in two places: Denisova
cave in Siberia, and Baishiya Karst
cave on the Tibetan plateau. Most
anthropologists think Denisova cave
was their northern limit, because
further north was too cold. Genetic
results suggest that they also lived
much further south than Tibet,
however, roaming huge areas of
Asia to Indonesia, which at the time
Denisovans were alive was attached
to mainland Asia because of low sea
levels. Lands further south were still
cut off, and there is no reason to think
they were in Australia.
To the east, there are multiple
potential Denisovan fossils from
China. These include several bones
from Xujiayao in north China and
two craniums from Xuchang in
central China. Like a jawbone
found off the coast of Taiwan,
none of these quite fits the profile
of a known species, so are good
candidates to be Denisovans. To the
west, an arm bone from Sel’Ungur
cave in Kyrgyzstan could be
Denisovan too, but attempts to
extract DNA from it have proved
unsuccessful.The oldest known
bracelet, dated
to 45,000 years
ago, was found
in Denisova caveSP
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