Biologically, modern humans are classified as homo sapiens of the humanoid genus, and modern humans are the only remaining humanoid creatures on Earth.
<h1 class="pgc-h-arrow-right" data-track="36" > a member of the human family who has appeared on the stage of history</h1>
But in fact, in ancient times, the genus not only Homo sapiens, but also 18 other species, namely Homo naledi, H. habilis), Mrs. Rudo (H. rudolfensis), the craftsman (H. ergaster), Homo gautengensis, Homo erectus (H. erectus), Homo antecessor, H. Sibraneau cepranensis), H. Rhodesians rhodesiensis), H. Heidelberg heidelbergensis), Neanderthal, F. Flores floresiensis), H. Penghu tsaichangensis), Denisova hominin, Red Deer Cave people, Luzonensis, and homo longi, just northeast of the Nesher Ramla Homo discovered in Israel some time ago. And there are also widely debated Homo georgicus and LD 350-1.
Dragon Man
Among them, Neanderthals and Denisovans, they are closely related to Homotharians, of which Neanderthals are the most fossil-rich ancient humans, in 1856, in 1856, in the Neanderthal valley near the city of Düsseldorf, Germany, the first discovery of The Fossils of Homo nean- derthalensis, the fossil is a male, thick body, brain volume of up to 1 230 mL, slightly less than or equal to the brain volume of modern humans. Their skull fossils show that the difference between them and modern humans shows that their faces are more primitive than modern humans, with a low forehead, a thick eyebrow ridge, a protruding jaw, a retracted cheek, and so on; but the overwhelming fact is that his brain is as large as that of modern people.
Neanderthals and Denisovans
The typical height of 1.60m, strong skeleton, developed muscles, and hardiness are the characteristics of Neanderthals, who lived in Europe, the Near East and Central Asia about 200,000 to 28,000 years ago, and "ruled" all of Europe, West Asia and Northern Africa from 120,000 years ago, but these ancient humans disappeared 24,000 years ago. The reasons for this are widely debated.
<h1 class="pgc-h-arrow-right" data-track="38" > Neanderthals and Homo sapiens to produce genetic exchanges</h1>
Archaeological studies have shown that Neanderthals and modern humans coexisted in Europe for at least 6,000 years, so scientists have been discussing the possibility of genetic exchange between the two.
Before DNA sequencing technology entered genetics, we generally thought that cross-species love would end in vain. Most knowledge will tell us that the evolutionary process of human beings is a straight line, from the very beginning of the reptile apes, to the final modern Homo erectus Homo sapiens, we are different species from Neanderthals, and it is impossible to produce offspring.
Beginning in 2006, however, scientists sequenced a neanderthal specimen in its entirety. The specimen was unearthed in a Siberian cave and is 130,000 years old. DNA analysis suggests that Neanderthals may have crossed with the ancestors of modern humans.
Through the analysis of Chinese volunteer samples, scientists found that Chinese and Neanderthals have certain genetic commonalities, and confirmed that the Chinese is the product of homo sapiens and Neanderthals "mixed blood", which makes researchers determine that Neanderthals have indeed combined with Homo sapiens. In 2017, sequencing of people from different regions showed that 1.8–2.4% of Neanderthal genes were measured in modern Europeans, compared with 2.3–2.6% in modern East Asian populations, including Chinese.
Homo sapiens first came out of Africa about 100,000-130,000 years ago, and they inhabited the Near East, where remnants of Homo sapiens activity dating back 100,000-130,000 years have been found in israel's Skhul Cave and Qafzeh Cave. But the good times did not last long, and Homo sapiens' journey out of Africa did not seem to be so smooth, and they encountered neanderthals who were expanding southward.
At that time, neanderthals were in their glory, and they had already ruled Eurasia, with a distribution that stretched from western Europe to the Altai Mountains in Siberia.
About 60,000 years ago, Homo sapiens left Africa for the second time and came to the Near East; at the same time, a second wave of Neanderthals spread to the Near East, such as the Kebara Cave on Mount Carmel in Israel. This time it was Neanderthals' turn to be unlucky, and they were driven out of the Near East by Homo sapiens.
But during this intersection, Neanderthals and Homo sapiens were mixed, about 49,000-54,000 years ago. It should be noted that the genetic exchange between Neanderthals and modern humans was not a single event, but a multi-event, and they have had genetic exchanges in both Europe and the Near East. Scientists have also found The Genes of Neanderthals (hereinafter referred to as Neanderthals) in Africans, which shows that the gene exchange between Homo sapiens and Neanderthals covers three major events: the interbreeding of Neanderthals and non-Africans, the return of Europeans to Africa, and the flow of genes from modern humans to Neanderthals who left Africa early.
<h1 class="pgc-h-arrow-right" data-track="40" > why there is no reproductive isolation between the two</h1>
So why did Homo sapiens and Neanderthals not have reproductive isolation? At that time, Homo sapiens and Ni people did not have strict reproductive isolation, and it may be that the differences in genes, chromosomes, etc. between the two at that time were not so large, and they were still able to hybridize and fuse to produce offspring with the ability to reproduce.
Of course, this does not mean that there is no "punishment" for this exchange, genes are selfish and exclusive, he does not allow genes of other species to enter the house, and the continuation of the population is a means for them to maintain their own survival and reproduction, so it will remove the Neanderthal genes from the offspring and reduce their fertility, thus ensuring the "purity" of the Homo sapiens genes.
Laurent Excoffier of the University of Bern in Switzerland argues that there are problems with fertility in the mixed-race offspring of Nepalese and modern humans.
Scientists have found in the sequencing of human genes that in the process of human evolution. In most functional genomes, the phenomenon of Nasiri ancestry is cleared; in contrast, the genetic traces of The Nepalese are heavier on the "garbage" genomes that have little effect. This is why only 1.8–2.4% of the Nigerian gene is in modern Europeans and only 2.3–2.6% in modern East Asians.
This is a very important point that shows that in the process of natural selection, the descendants of Neanderthals and modern people are not "welcome" (not living well), in other words, the Neanderthal genes in our bodies are constantly cleared by natural selection.
<h1 class="pgc-h-arrow-right" data-track="42" > neanderthal influence on Homo sapiens</h1>
Does this mean that modern people no longer have traces of The Ni people? No, Nature has published an article arguing that the Nepalese gene has caused modern people to suffer from type 2 diabetes, Crohn's disease, lupus, biliary cirrhosis, and other autoimmune diseases. See, the two diseases found are not heavy samples. Considering that we carry only 1.5% of the Nepalese gene, this contrast makes its impact on human diseases even more intense.
Does that mean that the union of Neanderthals with Homo sapiens has only negative effects on humans, and it is not, for example, that Neanderthal's ADAMTSL3 allele reduces the risk of schizophrenia in its owner. This allele also appears to affect human height to some extent.
So Chinese did you get any good genes from the Nepalese? Chinese inherited two skin genes from Neanderthals: POU2F3 and HYAL2. POU2F3 encodes transcription factors found in the exothletal layer and controls the growth and development of skin cells. 4 HYAL2 encodes an enzyme that breaks down substances between our skin cells and helps them respond to UVB. Compared to the modern human version, these two Neanderthal genes are present in as many as two-thirds of East Asians, which is a typical pattern of beneficial genes.
The Nepalese passed on to Europeans a major skin gene, BNC2, which encodes a skin cell transcription factor associated with light skin tone, sunburn and freckles. It affects the skin's skin tone saturation and the formation of pigmentation spots, and European skin becomes whiter. It is BNC2 that balances the reduction in daylight in these areas with their increased demand for vitamin D.
Skin genes inherited from the Nepalese in different regions
In addition, the main genetic risk factor for COVID-19 to develop severe disease in the context of COVID-19 is the gene cluster on chromosome 3, and the latest study published in Nature confirms that this risk is caused by about 50 kb-long fragments of the genome inherited from Neanderthals, which are highest in South Asian and European populations, but almost none in East Asia and Africa. This means that after covid-19 infection, Chinese less likely to develop severe illness than Europeans and South Asians.
<h1 class="pgc-h-arrow-right" data-track="44" > summary</h1>
Of course, with the development of time, modern humans have gone farther and farther on the road of biological incompatibility, and have strict reproductive isolation for other species, and human germ cells are equipped with "radar" that can identify non-homogeneous cells. Researchers at the Wellcome Trust Sanger Institute have found that proteins that interact on the surface of sperm and egg cells are necessary for life. These proteins allow sperm and eggs to recognize each other.
Therefore, if modern people travel back to ancient times in time and space, it is impossible to have genetic communication with the Nepalese people.
Resources:
[1] Caili Bi,Guangyan Guo,Xiao Zhang,Yanhui Tian,Yinzhu Shen. Research Progress in Neanderthal Genomics[J].Genetics,2012,34(06):659-665.
Feng Jiajun. The New Image of Neanderthals and Its Evolution[J].Guangdong Anatomy Bulletin,1987(02):72-73.
[3] David Reich. Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past[M].Zhejiang: Zhejiang People's Publishing House, 2019.
ZHANG Meng. A review of the difference between the cultural refinement of Neanderthals and modern people ?—— intellectual level or cultural expression[J].Chinese Journal of Anthropology,2019,38(01):60-76.
[5] Ding, Q., Hu, Y., Xu, S., Wang, J., & Jin, L. (2014). Neanderthal introgression at chromosome 3p21.31 was under positive natural selection in east asians. Molecular Biology and Evolution, 31(3), 683–695.
[6]. Vernot, B., & Akey, J. M. (2014). Resurrecting surviving Neandertal lineages from modern human genomes. Science, 343(6174), 1017–1021.