Page 43 - Archaeology - October 2017

Western Michigan University biological anthropologist and researchers suspecting that they came from elsewhere in Asia.
osteology expert on Aldenderfer’s team, explains, “When But according to Christina Warinner of the Max Planck Insti-
we’re challenged by the environment, if some individuals tute for the Science of Human History in Jena, Germany, who
have genetic traits that enable them to survive and repro- is responsible for DNA extraction from the human remains
duce more successfully than others who lack that trait, then from Upper Mustang, the genome sequencing has revealed
those with the beneficial traits live and pass those traits along that “genetically, these people are almost certainly coming
until it becomes more common in populations owing to the from the Tibetan Plateau—they look very similar to present-
advantage it confers.” day Tibetan populations.”
It can be observed that, compared with people who live Warinner works with Anna Di Rienzo of the University of
at sea level, Tibetans breathe more frequently and take in Chicago’s Department of Human Genetics, who directs the
more oxygen, and they have expanded blood vessels that team’s genomics research. By identifying the alleles that pro-
enhance the delivery of oxygen throughout the body. Andeans mote adaptation to high elevation and then comparing those
have higher levels of hemoglobin, the protein responsible of the closest modern population to those in the ancient
for transporting oxygen in the bloodstream, so their blood samples, the team has found that while cultures, religions, and
cells carry more oxygen than those of lowlanders. Studies behaviors shifted dramatically through the centuries, their
of highland Ethiopians, too, indicate genetic adaptations genetics did not. “Genetically they were very, very stable,”
to low-oxygen environments. Something must confer these says Warinner, “and that’s uncommon.” The researchers
adaptations. Eng says there are several telltale alleles found also found strong evidence that one of the adaptive alleles,
in high-altitude populations where hypoxia is a major chal- EGLN1, is present throughout all time periods studied. The
lenge. An allele is one of multiple versions of the same gene other—EPAS1, the gene that originated with Denisovans—
that determine various physiological traits—blood type in appears only in the most recent period studied. Warinner is
humans, for example, or the distinct color of a rose. Alleles not yet certain why this is the case.
can be thought of as recipes for the same gene—think of the
difference between spaghetti with meatballs and spaghetti ldenderfer and several of his colleagues created a
with ground beef. In evolutionary terms, random mutations stir in early 2017 when they announced that they had
create new recipes for alleles that may eventually come to Aevidence of preagricultural hunter-gatherers living in
exist throughout a population. a permanent settlement system on the central Tibetan Pla-
In the case of Himalayans, ancient and modern, two par- teau at least 7,400 years ago—thousands of years earlier than
ticular alleles have promoted adaptation to high elevation researchers had previously thought. That research centers on
and the avoidance of hypoxia. One of those alleles is known a site called Chusang, about 215 miles from Lhasa, at an eleva-
as EGLN1, which, Aldenderfer says, is estimated to have tion of 14,000 feet. There, 19 human hand- and footprints
appeared around 8,800 years ago. Another allele, EPAS1, has are embedded in a unique formation of travertine limestone
a fascinating origin story. It dates back to the Denisovans, created in the remains of ancient hot springs. No artifacts were
an extinct hominin species that lived in the Altai Mountains found nearby, just the markings of up to six individuals who
of Siberia some 45,000 to 50,000 years ago. Scientists do were at that site millennia ago.
not yet understand where or how, but it seems that, at some Without artifacts, the researchers had to rely on research
point, the Denisovans encountered early modern humans and, methods such as geochronology and a variety of other dating
somewhere along the way, their EPAS1 gene ended up on the techniques. Aldenderfer’s team hypothesizes that Chusang
Tibetan Plateau. was one stop in a permanent preagricultural occupation, and
that the prints were made by early hunter-gatherers who
ecovering the ancient DNA that allows for these settled on the plateau year-round. The finding is pivotal for
conclusions is meticulous work, and is hampered by the several reasons. First, it clarifies Chusang’s age, which had
R fact that many of the world’s highland environments, long been debated. Some previous research had pinned the
such as those in Ethiopia and Tibet, are politically unstable or site at 20,000 years old or more, which perplexed many
otherwise off-limits. Nevertheless, Aldenderfer’s team has been researchers, as that would have meant humans were present
able to conduct what appears to be the first investigation of the there during the height of the Last Glacial Maximum. The
ancient DNA of the people of the Himalayan arc. They have new dates—7,400 to 13,000 years ago—“are more consis-
sequenced the genomes of eight individuals who lived during tent with what we know about the broader region,” says the
three distinct cultural periods between 1,250 and 3,150 years University of Pittsburgh’s Loukas Barton.
ago, in what is now Upper Mustang, Nepal, at altitudes between But Barton finds the team’s interpretation of the new dates
about 9,000 and 14,000 feet. The team’s primary questions are: problematic because of the preagricultural part of the argu-
Where did these people come from? Did they have the adap- ment. Barton, like several others, hypothesizes that it was
tive alleles for high altitude? If so, which ones? And how do the the introduction of agriculture to high-elevation regions that
genetic findings relate to any artifacts found nearby? enabled early Tibetans to survive at such heights. Agriculture
There have been many hypotheses about the identities and was established in this region roughly 3,600 years ago, and
origins of early people living in these high valleys, with some Barton’s hypothesis for full-time occupation rests on the

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