What are the secrets of Australian aborigines' genes?

Milk a cow? The ambition of scientists: Is there a cure for epigenetic diseases? Genetic research has a clean history-the truth of AIDS epidemic in America-the genetic secret hidden in autumn red maple. Every nation has a long genetic history. Some people have frequent contacts with other ethnic groups, while others have been independent for a long time and have limited communication with others. Among people outside Africa, the first people to be separated from others were the Papuans in Oceania and the Australian aborigines. The genome of Papuans was sequenced earlier, with a large number. However, it was not until 20 1 1 that the first study led by Eske Willerslev was published.

Independent Australian aborigines and human beings all originated in Africa, but not necessarily from the same group of ancestors who set out together. The paper of 20 1 1 estimated the age of ethnic separation in various places, and found that Australian aborigines left tens of thousands of years earlier than the ethnic groups in Eurasia. This means that the ancestors of Australian aborigines and other non-African nationalities did not leave Africa at the same time [1]. However, the above inference is only supported by one sample, and the influence of ancient mixed blood is not considered, which may not be perfect.

Willers Lev's team made persistent efforts this year, and obtained the genomes of 83 Australian aborigines living all over Australia, hoping to get more reliable answers [2]. According to archaeological records, humans crossed the sea to Australia about 50 thousand years ago. At that time, Australia was also connected with New Guinea in the north, forming a huge continent called the Sahur Continental Shelf. To study the genetic history of Australia, we should consider Papua, the neighbor of New Guinea. The study also sequenced the DNA sequences of 25 Papuans to make the information more comprehensive.

After Europeans colonized Australia, Australian aborigines had frequent contact with the colonists, and they may have had contact with neighboring Asians or Papuans before. According to the analysis of the genome, it is found that there are signs of foreign mixed blood of Australian aborigines everywhere, mainly from three sources: the older Papua and the more recent ancestors of East Asia and Europe.

What happened on the long road from Africa to Australia after leaving Africa and before arriving in Australia? This paper compares indigenous peoples in Africa, Europe, East Asia and Australia. The result of the analysis is that all ethnic groups outside Africa originated from an ancestral group that experienced the bottleneck effect about 72,000 years ago, which shows that they left Africa at the same time. This argument is consistent with the Simmons and Estonia plans published at the same time [3].

Among the peoples who left Africa, the ancestors of Australian aborigines and Papuans were the first to be separated from others, about 58 thousand years ago; Later, 42,000 years ago, Europe and East Asia separated, forming three major gene branches outside Africa.

In addition, the hybridization between Homo sapiens and extinct ancient races is also a major focus in the study of gene history. The model used in this paper shows that Homo sapiens and Neanderthals were mixed twice. For the first time, 60,000 years ago, before all non-African peoples separated, Neanderthals shed 2.3% DNA to respect Homo sapiens. 5 1 0,000 years ago, when the Australian indigenous branch left and the Eurasian ethnic group was not separated, the Neanderthal DNA that received 1. 1% came again. The branch to Oceania met Denisova about 44,000 years ago and integrated 4% Denisova DNA.

Crossing the continental shelf of Lake Rusha, Australian aborigines were officially born. The close relatives of Australian aborigines are old neighbors Papua. Australian aborigines and Papuans belong to the same genetic branch and have the same amount of Denisovan DNA. Both of them can be traced back to a small group of people who experienced the bottleneck effect about 50 thousand years ago, which may be close to the time when they landed on the continental shelf of Husha Lake.

In the past, some people suspected that the current Australian aborigines were actually not the earliest inhabitants of Australia, but the invaders who eliminated the earliest immigrants; But this study found that the ancestors of Australian aborigines and Papuans had separated 37,000 years ago. It can be seen that all Australian aborigines who participated in this study are descendants of the same group who entered Australia tens of thousands of years ago. Therefore, the statement that "they replaced the original residents" should have been overthrown long ago.

The continental shelf of Husha Lake was separated from a piece of land into Australia and New Guinea because of the rising sea water, which happened 7000 to 1.45 million years ago, much later than the gene separation of the two populations 37000 years ago. It can be seen that human contact is not only affected by seawater barrier. However, even aborigines belonging to all parts of Australia have formed many independent ethnic groups with limited genetic communication with each other. The desert areas in the northeast and southwest with the biggest difference are even separated by 3 1000 years.

Language and blood are consistent but not consistent. The languages of the Australian aborigines sampled this time belong to the largest Pama-Nyungan language family in Australia. When Europeans arrived in Australia, there were more than 250 languages, about two thirds of which belonged to this language family. The relationship between language and consanguinity has always been an important topic in anthropology. The phylogenetic tree can be drawn by the distance between the DNA of each ethnic group; Similar language trees can also be made by the degree of word change in each language [4].

Australian aborigines have strange languages and blood relations. The blood relationship between ethnic groups is highly consistent with their geographical distribution, that is, the closer the geographical distance, the closer the blood relationship. The language tree and blood distribution made by each language are almost identical, which is reasonable so far, but it is puzzling that the age of the two is completely out of date.

Phylogenetic tree can not only judge the genetic relationship between branches, but also estimate the age of differentiation. The genetic differentiation of various ethnic groups in Australia ranged from 1 year to 30,000 years, which began to differentiate 30,000 years ago, and 1000 years ago took shape. The order of language differentiation is almost consistent with heredity, but the branching time is within 6000 years. At present, no one can clearly explain this phenomenon.

According to the inference process that Australian aborigines need to be further studied, all Australian aborigines' ancestors were separated from Papuans 37,000 years ago, and many branches began to form more than 30,000 years ago, and they were roughly shaped by 654.38+0,000 years ago. It is speculated that the earliest Pama-Nyungan language began to spread by a few people in a fixed order 6,000 years ago with a fixed population distribution, and gradually derived various languages, without involving the flow of DNA.

However, it is necessary to remind readers that scholars have different views on the related research of Pama-Nuan language; Every age estimated in this paper is also affected by the hypothetical "mutation rate" and "how many years each generation has", and there will inevitably be errors. But the value of these studies lies not in the accuracy of figures, but in the inferences drawn from them, which can help us understand the complex process of human evolution better.

Some Australian aborigines live in unfriendly deserts, and some genes detected in this study may help them survive, such as genes related to cold resistance and thyroid hormone regulation, or genes that increase serum uric acid concentration may be beneficial to adapt to arid environment.

Obtaining the genome of Australian aborigines this time is only the beginning. By exploring their DNA more deeply, we can not only have a deeper understanding of Australian aborigines, but also discover their potential applications in the future through our understanding of human past.

This article is reproduced from: GENEONLINE, the most professional media team in the field of genetics.

Subject: human origin, genes, heredity