Dongju Zhang, Dongju Zhang, Lanzhou University
The Denisovans hold a very strange place in the history of humanity. Like the Neanderthals, it is an early branch of the genealogy that produced modern humans and later merged with modern humans. But we’ve known Neanderthals for about 150 years, before we’ve traced their DNA sequence and identified the group of their physical characteristics from which they were defined. On the contrary, we had no idea that Denisovans existed until their DNA suddenly changed into a small piece of a finger. And, to this day, we haven’t identified enough leftovers to say anything about what they really look like.
However, over time, we have grown older DNA samples that provide a clearer picture of our interactions with this mystical lineage. Now, two new reports detail ancient DNA that provide some more details. One paper describes a modern human genome in Asia that is close to the time when interbreeding is essential. This provides further evidence that there were at least two instances of reproduction and helps to explain how the human population moves around Asia. The second confirms that the Denisovans lived along the Tibetan plateau and may have moved to higher altitudes.
Mongolian skull
In 2006, excavations in Mongolia’s Salkhit Valley led to the top of a skull that was apparently old. However, since there were no definite features, people debated whether it could be a dormitory or not. Standing man. However, early DNA sequencing indicated that it belonged to a modern human, with carbon dating to be about 34,000 years old.
This is indeed a critical period in the history of humanity. At this time, the East Asian and East Eurasian (or Siberian) populations were different, later it belonged to some West Eurasians. Their histories are very complex. A 40,000-year-old skeleton near Beijing is clearly the closest to modern East Asians but the closest is to a skeleton in Belgium (! ?? !!). A 45,000-year-old Siberian skeleton does not seem to have any modern relatives, while a 24,000-year-old man from the same region identified the population that was found to be born in East Asians. Native American ancestry. But two other Siberian skeletons at about the same time do not represent that love and only appear to be Eurasian in general.
If you are not confused after that, go back and read it again.
Given this disturbance, no other DNA of that period and area could be useful. Therefore, researchers have done what has become a standard method for preserving this old DNA. They first looked for sequences that matched human DNA to cut out human scenes. To eliminate contamination from modern humans, they again looked for signs of the most common damage in the form of the DNA age. Anything that was obviously human and damaged was used to add a genome.
The end result is that you get the top of the skull according to the age you expect. Most of the differences in DNA are similar to modern humans, but there were many areas that were similar to Neanderthals and Denisovans. The modern human fraction is the closest match between the Eastern Eurasian and Native American populations, confirming past results.
Excessive reproduction
But it’s still almost as confusing as ever. “The [newly described] The literate person shares many lambs with Tianyuan [Beijing] Individuals with 31,000,000-year-old Yana people in northeastern Siberia, “the researchers write,” yet Tianyuan and Yana people share fewer alleles with each other than the written person. “Overall, the researchers conclude that after some time the West and East Eurasian populations diverged, with some inter-productivity between East Eurasians and East Asians.
But of course, the newly described Siberian DNA has a unique resemblance to the Belgian skeleton, suggesting that at least some Western Eurasian DNA was still being passed down through the lineage.
More old
As far as Neanderthals are concerned, the new Siberian skeleton is quite unique to the modern Asian population, with about 1.7 percent of its DNA coming from Neanderthals. Denisovan’s content is difficult to judge, but researchers found 18 large pieces of DNA that were inherited from Denisovan. The size of these researchers concluded that interbreeding took place about 10,000 years ago. This is consistent with the complete absence of Denisovan DNA in the 45,000 year old Siberian skeleton. And the existing Denisovan DNA is more compatible with the amount seen later in East Asian cages.
Interestingly, the segments present in the newly written genome do not overlap with those found in the genomes of modern humans in Southeast Asia and the Pacific. The obvious implication is that modern man coincides with the Denisovans on at least two different occasions. This is something that was shown by other results, but modern East Asians have DNA from both of these events. The written genome provides a distinct distinction between them.
Meanwhile, a separate paper looks at where the Denisovans lived – especially in the Baishia Karst Cave on the edge of the Tibetan Plateau. At 3,000 meters (about 11,000 feet) above sea level, it was a very high altitude environment that would have been difficult to build during the last ice age. Yet there was found a part of a jaw bone. Although it did not take any DNA, the protein fragments indicated to the jaw that it belonged to a Denisovan.
DNA from dirt
Most older DNA samples are severely damaged by bacteria, with severely damaged and broken DNA. As a result, researchers have developed different processes to help differentiate human-like DNA and then identify older DNA based on the pattern of its accumulated damage. Gradually, it was realized that the same techniques could work where the contamination was higher and the human order even lower: soil samples. So, while we couldn’t extract the DNA from the jawbone, one team decided that there was something left in the environment from which it came.
So, the team tied rocks at the bottom of the cave, dating the different layers, to create an approximate historical sequence. Most layers contain mammalian DNA that is quite old in terms of damage. Therefore, researchers extracted human mitochondrial DNA and began to sequence it. This was obviously Denisovan, with a slight possibility of a small fraction of modern human DNA.
In all, the signs of Denisovan’s occupation date from about 100,000 years ago to about 30,000 years ago. This is a detailed history of the profession, although we do not know if it was continuous, seasonal or seasonal. Although 70,000 years is definitely a long time, researchers have called for higher altitudes. And it turned out to be in line with another genetic research: that some Tibetan genetic adaptations were at higher altitudes. Inherited from the Denisovans.
Science, 2020. DOI: 10.1126 / Science.ABC1166, 10.1126 / Science.BB6320 (About DOIs).
