Unknown Ancestor Found in the Human Genome

In early August, American researchers identified traces of a previously unknown ancestor in human DNA. Apparently, the ancient Sapiens interbred not only with Neanderthals and Denisovans, but also with someone else. Probably with Homo erectus – his genome has not yet been deciphered. Scientists have previously mentioned a mysterious archaic species that has left an admixture in the DNA of Melanesians and modern Africans. Who is this mysterious hominid and what modern people have inherited from him.

In 2016, experts from the University of Texas (USA) at the annual meeting of the American Society of Human Genetics stated: traces of hominids unknown to science were found in the DNA of Melanesians living on the Pacific Islands. Comparison of their genome with the DNA of Neanderthals, Denisovans and Africans led to this conclusion.

The researchers were going to find out what percentage of genes we inherited from extinct Homo. And they unexpectedly discovered that a significant part of the ancient genes that were considered Denisovan actually belong to another human species.

In the same year, Danish scientists made similar conclusions – regardless of the Americans. After analyzing about a hundred genomes of Papua New Guineans and Australian aborigines, they noticed an admixture of archaic DNA. At first glance, it resembled Denisov’s one, but judging by some differences, it was a different kind of hominid.

The 2016 studies raised many questions: the genome of a modern person, from whom they were looking for foreign genes, was compared with the DNA of those from whom he could get them.

By that time, the genome of the Neanderthals had already been well studied, but the main source of information about the Denisov people remained the phalanx bone of the finger and several teeth from the Altai cave. Given that Homo sapiens are believed to have mingled with Denisovans who lived in southern Asia or eastern Indonesia – distant populations often differ from each other – the traces of the mysterious hominid could well belong to them.

Scientists believe that Homo sapiens and their ancestral population have crossed several times with representatives of other Homo species. Thanks to this, there are sections in the DNA of modern people inherited from both Neanderthals and Denisovans.

However, four years later, researchers from the University of California at Los Angeles (USA) proposed a new technique for finding an ancient impurity in the DNA of modern people. It was no longer required to know the genome of the person from whom it was inherited. That is, scientists could find traces of hybridization of our ancestors with extinct species of Homo, from which nothing remained – no bones, no teeth, no tools.

The first people to test the new approach were the West African peoples of the Yoruba and Mende. Experts analyzed 405 of their complete genomes and isolated from two to 19 percent of previously unknown archaic DNA. This means that the ancestors of modern Africans interbred with the species of people that separated from the common trunk about 625 thousand years ago – before the appearance of the Neanderthals and Denisovans.

The ancestors of the West African Yoruba tribe interbred with so far unknown species of people who separated from the common trunk about 625 thousand years ago
Demographic modeling showed that hybridization took place no later than 43 thousand years ago – approximately at the time when in Europe Neanderthals began to mix with Homo sapiens.

True, what exactly the genes transmitted by the mysterious ancestor are responsible for, and what role they played in the survival of the West African peoples, is not yet clear.

Six months later, scientists from Cornell University (USA) applied a similar technique when analyzing the genomes of two Neanderthals, one Denisovan, and two modern humans. As a result, it turned out: ancient hominids of different species entered into sexual relations and exchanged genes whenever the two groups crossed in time and space. There are probably more cases of crossbreeding than is commonly believed.

So, Neanderthals had a sexual interest not only in sapiens: about 200-300 thousand years ago, they mixed with an unknown ancient species of hominids and inherited almost three percent of the genome from them.

Judging by the latest data, Denisovans and Neanderthals interbred with hominids of an unknown species, which separated from the common trunk even before their appearance (in the figure, they are designated as “unknown ancestor”). Thanks to direct hybridization (indicated by solid arrows in the figure), genes inherited from this mysterious ancient creature appeared in the DNA of Neanderthals and Denisovans. In addition, these DNA fragments were passed on to Homo sapiens – through crossing with Neanderthals and Denisovans (the transfer of genes through “second hands” is indicated in the figure by dotted arrows)
In addition, traces of hybridization were found in the DNA of the Denisovan man – one percent of the genome came from a mysterious archaic relative. And then, thanks to the crossing of Denisovans and Homo sapiens, 15 percent of these genes were passed on to modern people.

The authors of the work suggest that we are talking about Homo erectus, the direct ancestor of the Sapiens, who could have lived in Eurasia simultaneously with the early Neanderthals and Denisovans. True, it is impossible to prove this: researchers have not yet received and sequenced his DNA.

The paradox of a mask that blocks the corona 19 virus
With the spread of Corona 19, the use of disposable masks has exploded around the world. However, disposable masks that protect us from coronavirus and harmful air are being pointed out as one of the causes of air pollution.

Now wearing a mask is a must, not an option. Just a few months ago, masks were worn depending on the level of fine dust concentration in the air, personal health status, and health care purposes. However, in the era of Corona 19, masks have become the last shield to protect us from viruses that are spread through droplets, and it has become a daily life for everyone to wear masks.

As such, concerns are raised as it has been revealed that masks that protect us from corona, viruses, fine dust, and other harmful air inevitably cause air pollution.
You have to check the material of the disposable mask first.

Currently, most of the disposable masks on the market consist of a filter that blocks contaminants, a nose clip that holds the nose, and an earring band. Except for the wire used in the nose clip, most of the mask is made of chemicals.

The main component of the mask with KF (Korea Filter) 80 or higher, which is a standard for health masks distributed in Korea, is polypropylene and a melt blown nonwoven filter made by compressing it and converting it into an ultra-fine fiber nonwoven fabric.

Polypropylene extracted from petroleum is widely used in masks, sanitary napkins, and diapers because it does not emit endocrine disrupting substances harmful to the human body. In addition, the melt blown nonwoven fabric made from this component is an ultra-fine fiber with an inherent diameter of 3-5 μm, and is used as a high-performance, high-efficiency filter because it has excellent flexibility, impermeability, barrier properties, and filterability. However, it is a long-standing dilemma with new materials that these components, which are relatively safe from the user’s point of view, are not free from environmental pollution.

The main component of the mask is polypropylene and a melt blown nonwoven filter made by compressing it and converting it into an ultra-fine fiber nonwoven fabric. It is used as a high-performance, high-efficiency filter because it has excellent flexibility, impermeability, barrier properties and filterability.
The dilemma of disposable masks

Polypropylene, the main ingredient in masks, is known to take thousands of years to fully biodegrade in the ground. Therefore, this component is usually disposed of, and it is recommended to discard the mask as well. In Korea, according to the “Guidelines for Separate Disposal of Recycling Products” issued by the Ministry of Environment, masks are registered as general garbage, put in a pay-as-you-go bag, and then incinerated.

However, in the incineration process, polypropylene produces dioxins, a highly toxic chemical. In particular, once dioxins are leaked into the environment, they do not decompose for decades and retain their properties, so there is a potential for substances dissolved in soil and rivers to be absorbed into our bodies through animals and plants.

As is known, dioxin is a substance designated as a first-class carcinogen by WHO. If this substance is absorbed into the human body, it has a fatal effect on health such as birth defects, causing cancer, metabolism and hormonal abnormalities, and is a very dangerous substance that can threaten not only humans but also the ecosystem.

The dilemma of a disposable mask that protected us from polluted air and viruses has begun to return to air polluting substances.

The dilemma began when the disposable masks that protected us from contaminated air and viruses returned to air polluting substances.

Reviewer overview

Unknown Ancestor Found in the Human Genome - /10

Summary

In early August, American researchers identified traces of a previously unknown ancestor in human DNA. Apparently, the ancient Sapiens interbred not only with Neanderthals and Denisovans.

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