Mysterious cousin of mankind “lost” for many years

Archaeological discovers new cousin

  Mankind wears clothes, eats cooked food, lives in buildings, and consciously learns knowledge, researches various problems, and invents objects… On earth, mankind is so special. But tens of thousands of years ago, our ancestors may not have been very special, because the distant relatives Neanderthals and Flores who did similar things with them lived nearby. These relatives are extinct, and fossils and traces of life let us know that they once existed. Just when we thought we had all the relatives who had lived on the earth together, the archaeologists found clues left by a mysterious distant cousin.
  In 2008, archaeologists unearthed a small piece of phalanx in Denisova Cave in south-central Siberia, Russia. It is estimated that the phalanx has a history of 76,200 to 51,600 years. After testing, the owner of the phalanx turned out to be an unprecedented human being. Such ancient humans are called “Denisovans”. The earliest time they lived in Denisova Cave may be traced back to 217,000 years ago. This caused an uproar in the archaeological community.
  In recent years, archaeologists have drawn many surprising conclusions about the Denisovans. For example, some of our genes are derived from the Denisovans, including controlling some appearance characteristics and certain diseases. Gene. For another example, genetic analysis shows that such ancient human footprints once spread all over Eurasia, Australia, and Southeast Asia. Before the Denisovan’s finger bones were discovered, archaeologists knew nothing about this ancient human being. However, this is also understandable. After all, very little evidence related to the Denisovans has been discovered, and there are only a few fossils. Fortunately, with the help of new technology, archaeologists have opened a window for us to understand this mysterious cousin. Let’s take a look at what Denisovans are like.
Ancient humans with big flat faces and no chins

  Speaking of ancient humans, we may have thick hairs, low foreheads, thick eyebrows, protruding mouths…So, what do Denisovans look like?
  So far, archaeologists have only a few fragments of Denisovan bones, and even rarer ones contain DNA. Archaeologists are also troubled by how to restore the Denisovans from these fragments. Fortunately, in recent years, the technology for studying ancient remains has continued to advance. Now archaeologists can infer the general appearance of ancient humans through DNA methylation instead of relying on DNA alone. DNA methylation is a form of DNA chemical modification that can control gene expression without changing the DNA sequence, thereby changing genetic performance.
  It can be said that the characteristics of our body, including bone morphology, are related to DNA methylation. In 2014, Israeli researchers constructed a partial DNA methylation map based on the DNA from the remains of Denisovan. After that, they compared the DNA methylation profiles of Denisovans, Neanderthals and modern humans, and found that there were 34 DNA methylation in the Denisovan skulls that were similar to those of modern humans and Neanderthals. different. By comparing the appearance of modern people and Neanderthals, plus the fact that the Denisovans have huge molars, the researchers roughly restored the Denisovan’s face-low forehead, wide and flat His face, almost no chin.

The image of a Denisovan girl restored by scientists based on DNA

  In order to verify this result, the researchers also constructed the methylation profiles of Neanderthals and chimpanzees, and compared the facial bone anatomy data of these two creatures that scientists have mastered. It was found that in terms of predicting the skeletal morphology of these two organisms, approximately 85% of the methylation feature reconstructions were consistent with the anatomical features.
  However, this method also has disadvantages, that is, it can only show the general situation of the bones of the organism, and cannot get accurate data, such as how long their fingers are in centimeters, how many centimeters are their faces, and so on. Therefore, if you want to know what the Nisovars look like, you need to wait for more bone fossils to be discovered.
Important discoveries on the roof of the world

Three-dimensional surface model of the mandible of Xiahe Denisovan with calcium carbonate nodules removed (grey is the mirror image part of the virtual reconstruction)

  The Qinghai-Tibet Plateau is known as the third pole of the world. There is high altitude, low temperature, and more importantly, the oxygen there is thin, but the Sherpas and Tibetans living there can easily cope with such an environment. It is beneficial to them that there are some special genes in their bodies-genes tbx15 and wars2 that help the body produce fat, as well as the mutant gene EPAS1. Among them, EPAS1 helps control the amount of hemoglobin in the blood. This is very important for people who live on high altitudes for a long time, because if the hemoglobin in the system is increased for a long time to deal with hypoxia, then the risk of heart disease will increase. So, why do Sherpas and Tibetans carry EPAS1 mutant genes?
  In 2014, scientists discovered that the tbx15, wars2, and EPAS1 mutant genes carried by Sherpas and Tibetans all came from Denisovans. But at that time, the only place where Denisovans were found was Denisovan Cave, which is only seven or eight hundred meters above sea level. Scientists wondered why the Denisovans needed these genes? How can Sherpas and Tibetans get involved with Denisovans?
  In 2019, archaeologists at Lanzhou University in China finally found some clues. They studied a mandible from the Baishiya cave (3250 meters above sea level) in Xiahe County, Gansu Province. The results show that this is a human bone, and it has a history of about 160,000 years, which has advanced the earliest time of human activities on the Qinghai-Tibet Plateau by about 120,000 years!
  So, who is the owner of this mandible? Did they pass on the genes for protection against cold and hypoxia to the Sherpas and Tibetans? Originally, archaeologists hoped to use the usual method of extracting DNA from the fossil to confirm the owner of the fossil. However, due to the age, the DNA in it has not been preserved. Fortunately, in recent years, scientists have developed a new archaeological method-analysis of ancient proteins.
  Compared with DNA, ancient proteins in fossils last longer. The chemical structure of the amino acids that constitute the protein is ultimately determined by the specific coding sequence in the DNA of the organism. Therefore, by comparing the amino acid composition of the same protein of different species, the distance between species can be judged. Fortunately, after hundreds of thousands of years, protein can still be extracted from this mandible fossil. After analysis and comparison, archaeologists discovered that the owner of this mandible is our mysterious distant relative, Denisovan! This is the first time that archaeologists have found a fossil of the Denisovan outside of Denisovan Cave.

  Archaeologists believe that Denisovans may have lived on the Qinghai-Tibet Plateau for a long time, which enabled them to acquire a mutant gene adapted to the harsh environment of the Qinghai-Tibet Plateau. In the process of interacting with the Sherpa and Tibetan ancestors, They passed these mutant genes to Sherpas and Tibetans. This discovery also shocked the archaeological community, because it filled the history of Denisovan migration, and also rewritten the history of ancient human activities and spread on the Qinghai-Tibet Plateau.
Autistic craftsman?

Archaeologists sampled the paleo-sedimentary layers of Baishiyadong in Xiahe County, Gansu Province

  In fact, in addition to sharing genes adapted to the plateau environment with modern humans, the genes that control dark complexion, brown hair, and brown eyes in modern humans may all originate from Denisovans, a study by researchers at the University of Washington in the United States. The results of the study show that the autism genes of modern humans may also come from the Denisovans.
  The Denisovans contributed a lot to the Melanesian genome, up to 4% to 6%. So the researchers analyzed the genomes of modern Melanesians, looking for something called copy number variation, hoping to trace the status of the Denisovans through these genetic clues. Copy number variation can show that the copy number of a complete gene of an individual is different from that of other individuals. Through these differences, some characteristics of the individual can be inferred. For example, compared with healthy people, people with Huntington’s disease have an abnormally increased number of sequence copies in a specific coding region of the IT15 gene.
  After analysis, the researchers found that in 79% of the Melanesian genome, there are as many as 383,000 base pairs of chromosome 16p11.2, which is much more than that of people in other regions. And this duplication abnormality originated from the Denisovan genome. So, what is special about the 16p11.2 copy number variation? It turns out that 16p11.2 is located in a genomic region related to autism, and the duplication and deletion of 16p11.2 during replication may cause autism.
  So, do Denisovans suffer from autism? Researchers believe that in the case of 16p11.2 replication abnormalities, Denisovans may be similar to modern humans with autism, with language, communication, and social difficulties. The abnormality of this gene may be related to their long-term living in a high-altitude, cold and extremely closed environment.
  In view of the fact that some autistic patients show “superpowers” in certain aspects, such as talent in painting, super memory, etc., some people have also asked whether the Denisovans also have similar “superpowers”? Archaeologists seem to have found some evidence.
  In Denisovan Cave in Russia, archaeologists discovered that they experienced a period of rapid technological development before the last group of Denisovans in Siberia disappeared 45,000 years ago. Among them, in the cave, archaeologists found bracelets showing complex drilling, carving and polishing techniques; also found delicate bone needles used to sew things; musical instruments similar in shape to modern whistles and flutes; compact Stone blades; tubular beads made from ostrich eggshells; etc. And some of these technologies are also pioneering, such as the use of eggshells to make beads and stone chips to make small blades. According to research, these technologies spread from Denisovan Cave to southwestern Europe and Asia, and spread eastward to northern China and the Russian Far East. This may indicate that the Denisovans are good at invention and creation. Perhaps this is the gift that the 16p11.2 copy exception gave them.
  We still know very little about the Denisovans. What kind of ancient humans who once lived on the earth with our ancestors need more archaeological discoveries and groundbreaking research to answer. And through the study of Denisovans, perhaps we can also find a way to treat autism or other diseases related to Denisovans’ genes.