Dongju Zhang’s group (Lanzhou College)
For nicely over a century, we had the chance to review Neanderthals—their bones, the objects they left behind, their distribution throughout Eurasia. So, after we lastly obtained the sequence of their genome and found that we share a genetic legacy with them, it was straightforward to position the discoveries into context. In distinction, we had no thought Denisovans existed when sequencing DNA from a small finger bone revealed that one more relative of recent people had roamed Asia within the latest previous.
Since then, we have discovered little extra. The frequency of their DNA in trendy human populations counsel that they had been doubtless concentrated in East Asia. However we have solely found fragments of bone and some tooth since then, so we won’t even make very knowledgeable guesses as to what they may have seemed like. On Wednesday, a global group of researchers described finds from a cave on the Tibetan Plateau that had been occupied by Denisovans, which inform us a bit extra about these kin: what they ate. And that seems to be something they may get their arms on.
The Baishiya Karst Cave
The finds come from a web site referred to as the Baishiya Karst Cave, which is perched on a cliff on the northeast of the Tibetan Plateau. It is situated at a excessive altitude (over 3,000 meters or practically 11,000 toes) however borders a excessive open plain, as you’ll be able to see within the image beneath.
Oddly, it got here to the eye of the paleontology neighborhood as a result of the cave was a pilgrimage web site for Tibetan monks, certainly one of whom found a portion of a decrease jaw that finally was given to a college. There, folks struggled to grasp precisely the way it match with human populations till finally evaluation of proteins preserved inside it indicated it belonged to a Denisovan. Now referred to as the Xiahe mandible, it stays probably the most substantial Denisovan fossil we have found thus far.
Dongju Zhang’s group (Lanzhou College)
Since then, excavations on the web site had turned up a big assortment of animal bones, however none that had been recognized as Denisovan. Sequencing of environmental DNA preserved within the cave, nevertheless, revealed that the Denisovans had occupied the cave usually for at the very least 100,000 years, that means they had been surviving at altitude throughout each of the final two glacial cycles.
The brand new work focuses in on the bones, a lot of that are too fragmentary to be definitively assigned to a species. To take action, the researchers purified fragments of proteins from the bones, which include giant quantities of collagen. These fragments had been then separated based on their mass, a way referred to as mass spectrometry, which works nicely even with the extremely small volumes of proteins that survive over a whole bunch of hundreds of years.
Mass spectrometry depends on the truth that there are solely a restricted variety of combos of amino acids—typically just one—that may produce a protein fragment of a given mass. So, if the mass spectrometry finds a sign at that mass, you’ll be able to examine the doable amino acid combos that produce it to recognized collagen sequences to search out matches. A few of these matches will find yourself being in locations the place collagens from totally different species have distinct sequences of amino acids, permitting you to find out what species the bone got here from.
When used this manner, the approach is termed zooarchaeology by mass spectrometry, or ZooMS. And, within the case of the work described within the new paper, it recognized practically 80 p.c of the bone fragments that had been examined.
