Excessive-altitude cave utilized by Tibetan Buddhists yields a Denisovan fossil

For properly over a century, we had the chance to check Neanderthals—their bones, the gadgets 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 simple to put the discoveries into context. In distinction, we had no thought Denisovans existed when sequencing DNA from a small finger bone revealed that yet one more relative of recent people had roamed Asia within the latest previous.

Since then, we have realized little extra. The frequency of their DNA in fashionable human populations counsel that they had been possible concentrated in East Asia. However we have solely found fragments of bone and some enamel since then, so we will not even make very knowledgeable guesses as to what they could 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 kinfolk: what they ate. And that seems to be something they might 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 almost 11,000 toes) however borders a excessive open plain, as you’ll be able to see within the image under.

Oddly, it got here to the eye of the paleontology group as a result of the cave was a pilgrimage web site for Tibetan monks, one among whom found a portion of a decrease jaw that ultimately was given to a college. There, folks struggled to know precisely the way it match with human populations till ultimately evaluation of proteins preserved inside it indicated it belonged to a Denisovan. Now referred to as the Xiahe mandible, it stays essentially the most substantial Denisovan fossil we have found up to now.

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 commonly for a minimum of 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, lots 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 in accordance with their mass, a method referred to as mass spectrometry, which works properly even with the extremely small volumes of proteins that survive over lots of of 1000’s of years.

Mass spectrometry depends on the truth that there are solely a restricted variety of mixtures 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 mixtures that produce it to recognized collagen sequences to seek out matches. A few of these matches will find yourself being in locations the place collagens from completely 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 method is termed zooarchaeology by mass spectrometry, or ZooMS. And, within the case of the work described within the new paper, it recognized almost 80 % of the bone fragments that had been examined.