A fossilized jawbone found in a cave in Tibet may offer scientists clues as to what the mysterious ancient human species called Denisovans looked like, a new study revealed.
In 1980, a monk meditating inside the Baishiya Karst Cave in Xiahe, China discovered the fossil of a human jawbone with giant molars and passed it on to scientists at Lanzhou University. Since 2010, researchers have been studying the Tibetan cave site where the mandible originated in the hopes of finding out more information about the Denisovans.
The caveat: after examining the fossilized Denisovan mandible, scientists discovered that its DNA was not preserved. Therefore, there has been no surefire way of identifying the fossil, except perhaps through the analysis of its proteins. This marks the first time that this technique is used to identify ancient specimens.
Using Protein Analysis To Examine The Denisovan Jawbone Found In Tibet
Everything that archaeologists know about the Denisovans has come from studying a handful of teeth and bone fragments from the Denisova cave in the Altai Mountains in Russia. Now, the discovery of the mandible in the Baishiya Karst Cave may help scientists picture out what these ancient human species looked like before.
The Denisovan specimen found in the cave consists of half a lower jaw plus two complete teeth. Scientists Fahu Chen and Dongju Zhang from Lanzhou University studied the specimen, but without any DNA, they had no way of comparing its genetic sequences with that from other ancient humans.
Instead, Zhang and her colleagues studied ancient proteins from the mandible, which they explained tended to last more than DNA. The research team found traces of collagen proteins in the dentine from the teeth and then compared the collagen protein with equivalent proteins from Denisovans and Neanderthals. Researchers found that the protein analysis lined up more with sequences from Denisovans.
More information was pierced together about the Denisovan fossil found in the cave. For instance, researchers said that one of the teeth was still erupting, which meant that the fossil likely belonged to an adolescent.
"The Xiahe mandible likely represents the earliest hominin fossil on the Tibetan Plateau," Chen said.
The success of the new study, which has been released in the journal Nature, could lead to greater emphasis on extracting ancient proteins out of fossils that have not yielded DNA. Paleoanthropologist Chris Stringer from the Natural History Museum in London, who was not involved in the new study, explained that the method could prove useful for older samples found in southeast Asia where DNA degrades quickly.
Still, Stringer said DNA analysis remains the "gold standard" in identifying ancient fossils. He added that although there is no genetic material in the mandible, scientists could perhaps find DNA in the sediments inside the Tibetan cave.
Ancient Human Species Denisovans Are Related To Modern Tibetans
Archaeologists have been searching for more Denisovans ever since paleogeneticists extracted DNA from the pinkie of a new kind of human who lived more than 50,000 years ago in the Denisova cave. Ever since, scientists have identified that Denisovans are an extinct sister group of Neanderthals.
The fossil of the Denisovan mandible found in Tibet is likely at least 160,000 years old, researchers said. It was discovered at least 3,280 meters above sea level, and researchers believe that Denisovans had adapted to living in this high-altitude low-oxygen environment long before Homo sapiens even arrived at the region. Furthermore, previous genetic studies revealed that modern Tibetans and other Himalayan populations carry the EPAS1 allele in their genes, which must have been passed on to them by Denisovans and helped them adapt to the environment.