A fossil jaw found in the Himalayan highlands of Tibet belongs to a vanished human species called Denisovans, deepening the mystery of human evolution in Asia, scientists said Wednesday in a new study probing the roots of humankind.
Discovered by a local Buddhist monk, the fossil shows these archaic human relatives lived on the roof of the world in the rarefied air at almost 11,000 feet—an altitude that would leave many people today starved for oxygen. They settled at these frigid heights at least 160,000 years ago, more than 120,000 years before modern humankind arrived, said the scientists, who published their work on the fossil in the journal Nature.
While this early human species became extinct long ago, traces of their DNA survive in modern populations of Asia, the Pacific and Australia, several genome studies show. In fact, many people of Tibet today owe their unusual adaptation to such extreme high-altitude conditions, where there is 40% less oxygen in the air than at sea level, to a unique gene inherited from these primordial mountain dwellers.
“One of the most spectacular aspects of this discovery is the location,” said project co-leader Jean-Jacques Hublin, director of the department of human evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “Nobody ever imagined that archaic humans would be able to dwell in such an environment.”
The discovery is the most recent to highlight the early history of human development in Asia, which has been long overshadowed by human-fossil finds in Africa and Europe. “It became the sleeping beauty of paleoanthropology,” Dr. Hublin said. “We are now turning to Asia again.”
Until the new find, the Denisovans were known only through a fossil fingertip, three teeth and a toe bone found in 2008 far from Tibet in a cave in the Russian Altai Mountains of Siberia.
In 2010, scientists successfully exhumed DNA from that finger bone and discovered a special variation of a blood-cell gene called ESPA-1 that affects the body’s response to falling oxygen levels, key to survival at extreme altitudes. Inherited by many Tibetan people, it is considered by some researchers to be the strongest instance of natural selection ever documented in a human population.
No DNA was recovered from the latest find, the researchers said. But they speculate that Denisovans likely lived at this extreme altitude long enough to develop that special genetic adaptation and then passed it on to more modern humans with whom they interbred.
It took almost 40 years for the fossil jaw to go from the hands of the Buddhist monk who first picked it up to publication in a peer-reviewed scientific journal.
According to project co-leader Dongju Zhang at China’s Lanzhou University, the monk found the fossil in 1980 while visiting the Baishiya Karst Cave in Xiahe, Gansu, China. The deep cavern is a sacred site managed by a nearby temple. The steep approach to the cave entrance today is festooned with streamers of yellow, blue and red prayer flags.
“He grabbed something on the floor,” Dr. Zhang said. Recognizing something unusual about the primitive jawbone encrusted with mineral carbonate, “the monk gave it to the local living Buddha.” Known formally as the Sixth Gung-Thang Living Buddha, the religious leader in turn gave the jawbone to Lanzhou University.
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Not until 2010 were university resources available to study the find.
Due to the unusual circumstances of the discovery, the researchers acknowledge they can’t prove that the jawbone came from the cave. But they were able to match the minerals on the jaw to deposits in the cave. Their recent excavation in the cave turned up stone tools and the bones of animals likely butchered for food dating to the same age as the fossil jaw.
“It blows my mind,” Dr. Hublin said.
Write to Robert Lee Hotz at sciencejournal@wsj.com
https://www.wsj.com/articles/ancient-humans-dwelled-at-great-heights-scientists-find-11556730001
2019-05-01 17:00:00Z
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