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Apr 6, 2020
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Ancient squirrels pointed to the grandfather of Neanderthals and sapiens

Last year, several scientific publications were published at once, in which the remains of ancient creatures were investigated using proteomic analysis. This technique is a kind of loophole for paleogenetics. Even in the remains in which DNA was not preserved , traces of proteins can still remain, and their amino acid composition can be compared with the composition of proteins of modern organisms. Thus, scientists recognized the jaw of a Denisovan found in a Tibetan cave and clarified the genealogy of a giant petite 1.9 million years old - it turned out to be a native of the orangutans. I assumed then that the next in the list of ancient proteomes would be a hobbit from the island of Flores or Homo naledi from South Africa. Well, I was wrong.

Seeing the publication that will be discussed, I even thought: is it not a hoax? (the article was published in Nature on April 1). The specialists managed to obtain the proteome from two samples at once - the tooth Homo antecessor from Atapuerca in Northern Spain and the tooth Homo erectus from Dmanisi in Georgia.

Both monuments are, without exaggeration, legendary.

in the small cave of Gran Valley (Atapuerca) in 1994 the year they found the remains of hominin, described as a special kind of person - Homo antecessor . The bones belonged to a teenager who, judging by the characteristic traces on the bones, about thousand) . years ago became a victim of cannibals. Researchers noted progressive features in the structure of the young man's face, which brought him closer to modern people, as well as some neanderthaloid features. A hypothesis has been voiced: is this not the common ancestor of the Sapiens and Neanderthals? The dating is suitable, but the place is not very: in order to become sapiens, a group of antecessors needed to return to Africa. So maybe it's just a Neanderthal great-grandfather? And not a native, but a cousin? It is difficult to answer, given that the remains of Homo antecessor are known so far from one cave in Atapuerk.

The question remained controversial, and here, for lack of DNA , paleoproteomics could help. As a sample, specialists took the molar from Gran Valley ATD6 - 92, which even managed to be directly dated by a combination of paramagnetic resonance and uranium series. Happened 772-800 thousand years.

The second location is no less impressive, because it is a Georgian monument Dmanisi - the oldest point in Eurasia, where the remains of people are found. The early Homo (the authors of the article refer them to Homo erectus ) lived in Dmanisi at least 1, 04 Million years ago! From here, too, a tooth was taken for proteomic analysis. The study, in compliance with all precautions, was carried out in two independent laboratories, comparing the result with a control sample - 300 - a summer human molar and a number of other famous finds related to the Holocene.

Luck smiled at the researchers: traces of proteins were found in the enamel of both teeth, by all indications - ancient. This was also indicated by the length of the read fragments of amino acid sequences shorter than those of the modern “control”: proteins break down over time. In this case, the sequences from the Dmanis tooth were shorter than from the Spanish one. It’s logical, because the Dmanis erectus is a million years older.

What did the analysis of proteomes show? Firstly, judging by the presence of specific proteins encoded on the Y chromosome, the individual from the Gran Valley was male.

Well, what about the pedigree Homo antecessor ? To clarify it, the researchers used genomes to compare 92 modern humans, anthropoid apes (including gibbon), rhesus monkeys, as well as three Neanderthal genomes and one Denisovan. Comparing the sequences of the corresponding proteins with each other, we constructed variants of evolutionary trees, where the antecessor was in different relationship with other hominins. The most likely turned out to be a scheme in which a young man from the Gran Valley turned out to be the closest sister taxon in relation to a branch that includes all the famous Homo . Simply put, the antecessor turned out to be the closest relative to the last common ancestor of the Sapiens, Neanderthals and Denisovans. This is consistent with genetic dating, according to which, the separation of the lines of sapiens and Neanderthals / Denisovans happened 550 - 580 thousand years ago . The combination of sapient and Neanderthal characteristics of a young man from Gran Dolin becomes clear: the features of distant descendants have already been guessed in his gloomy face!

Место антецессора наэволюционном дереве гоминин The place of the antecenter on the evolutionary hominin tree, according to research.

And could it have turned out differently? It could. If an individual from Atapuerca were, say, in a closer relationship with Neanderthals than with sapiens, he would fall “inside” the human branch - and then those who linked the Spanish hominids only with Neanderthal history would be right.

I must say that in this version, not everything is smooth. If you look at the drawing, you will see that the Neanderthal man from the Spanish cave El Sidron on it is not united with two other Neanderthals (Vindia and Altai), but with a Denisov man. The authors attribute this incident to the lack of resolution of the method. For a more accurate result, amino acid polymorphisms were not enough - unique features characterizing the sequences of proteins of different hominins.

Место Homo erectus из Дманиси наэволюционном древе гоминин Место Homo erectus из Дманиси наэволюционном древе гоминин

Place Homo erectus from Dmanisi on the evolutionary hominin tree.

Worse in this regard, the situation with the Dmanis sample. True, the researchers also managed in this case to build some version of the evolutionary scheme: in it Dmanisi also turns out to be an external sister taxon in relation to the group of the rest Homo . But the reliability of the result, as the authors themselves note, is low, due to the fact that the selected amino acid sequences are too short, and unique polymorphisms are completely absent. Apparently, therefore, the Dmanis proteome is not even mentioned in the press release about the study.

Nevertheless, we have a really revolutionary result: for the first time, a proteome was able to isolate from human remains of such antiquity. A good source for such a study was tooth enamel. The safety of certain peptides and their chemical characteristics are such that, according to researchers, they will allow us to study the features of the formation of teeth in ancient hominins. On the other hand, researchers are faced with significant limitations of the methodology, because of which miracles and sensations, which we all are waiting for, may not happen. Of course, I will still hope for you, the future proteome of the hobbit from the island of Flores!

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