The weird “legacy” of the Neanderthals

  Speaking of Neanderthals (Neanderthals for short), everyone has some understanding, but as a kind of extinct relatives of Homo sapiens, they still left us a legacy? This is incredible, what will it be?
Time-honored legacy

  This “heritage” left by the Nepalese is one of the longest-preserved heritages. How long is it? Approximately 40,000 years. This legacy that has been passed down for so long is in our blood, and almost all modern people have a share of the pie. Having said that, you may have guessed that this “legacy” is the DNA of Neanderthals.
  In 2002, archaeologists found a mandible of an early modern human in a cave in Romania. Carbon-14 dating shows that the mandible to which this mandible belongs lived was about 40,000 years ago. Scientists tested his DNA fragments and found that it contained 6%-9% of Nepalese genes. This ratio shows that the 4th-6th generation of ancestors of this ancient man had mated with Ni people. In other words, one of his great, great-great-grandparents must be Ni people. This is the recent evidence of gene exchange between Homo sapiens and Nigerians discovered by scientists.
  Strangely, scientists have discovered that, with the exception of some populations in sub-Saharan Africa, 2% to 4% of Nepalese genes are present in almost all human genomes today. According to the law of inheritance, this is almost impossible. Each child inherits 50% of the parents’ genes and 25% of the grandparents’ genes. In other words, every time a gene is passed on to a generation, the proportion of the same gene between the offspring and the parent will be halved. If 100 years is regarded as a reproductive generation, 400 generations have passed since 40,000 years. At that time, 6%-9% of the Nepalese genes have been inherited to this day, how could there be 2%-4% of modern humans? Woolen cloth?
  The reason is not difficult to guess. These genes left by the Nigerians are conducive to the survival of modern people. People who retain these genes can more easily leave offspring through natural selection, so these genes are also retained. We already know that Homo sapiens originated in Africa, and the living conditions and biological types in Africa are very different from those of Europe. Therefore, when Homo sapiens ancestors migrated from Africa to Europe, they were very uncomfortable. The disease caused by the new pathogen made Homo sapiens miserable. At this time, the genes of the Nigerians helped a lot. The Nigerians who have lived in Europe for thousands of years are already very familiar with the local diseases and pathogens. Their DNA is engraved with information about the fight against disease-causing viruses and bacteria. Homo sapiens easily obtained it by mating with the Nigerians. The genes that fight against new viruses and bacteria and the antibodies encoded by the genes have gradually adapted to life in Europe.

  Scientists have also discovered that the genes of the Homo sapiens also helped Homo sapiens adapt to European food. For example, the gene encoding the olfactory receptor 12D3 came from the Homo sapiens. This gene is conducive to Homo sapiens adapting to European food. There are also some genes from Nigeria that are thought to have the function of reshaping the shape of Homo sapiens’s teeth, and the altered teeth can chew European crops better. In addition, a type of gene MCPH1 that ensures the normal development of the brain also comes from Neanderthals. This gene makes Homo sapiens smarter and allows them to survive and develop in new areas that they have never been in contact with.
Side effects of legacy

  However, with the changes of the times, the heritage left by the Nepalese has also quietly “changed”, it is no longer as sweet as it was at the beginning.
  In 2016, a research team in the United States found some evidence that Nepalese DNA may cause disease by comparing the DNA of Nigerians and disease records in nearly 30,000 Europeans. They believe that certain DNAs of Nigerian people increase the risk of modern people’s physical and mental health problems such as heart disease, obesity and depression.
  Certain DNA from Nigeria is indeed related to disease, but it does not mean that it is bad in itself, but it is no longer adapted to modern life. The Nigerians struggle with wild beasts for a long time and often get injured. Their genes have the effect of strengthening blood clotting function. The ancestors of Homo sapiens retained these genes to protect them from losing their lives due to excessive blood loss during hunting and injury, and can quickly stop bleeding after childbirth. But now that we have stepped into modern society, we have many supplementary treatments when we lose blood, and we no longer rely solely on our own blood clotting ability. At this time, the excessive blood clotting function has become an accomplice in causing cardiovascular and cerebrovascular diseases. The genes in Nepal are good for absorbing glucose, which improved people’s survival rate in the ancient times of food shortage, but in the modern society with abundant food and over-nutrition, it has increased the probability of obesity and even diabetes.

  In 2020, the new coronavirus has caused a pandemic around the world, but the incidence of the disease is not the same among populations. How does the virus select its victims? Scientists at the Max Planck Institute in Germany have sequenced people’s genes and found that people who are susceptible to the new crown virus and have more severe symptoms after contracting new crown pneumonia have six identical genes on chromosome 3. These genes are positive. It is one of the legacy left by the Neanderthals.
  Scientists also found a gene directly related to the new coronavirus infection, DPP4, which encodes a protein involved in immune function and glucose metabolism. Previous studies have confirmed that the protein encoded by the DPP4 gene is the receptor of the MERS coronavirus, a close relative of the new coronavirus, and is a key mediator of inflammatory lung injury. After taking the DPP4 inhibitor, which is used to treat diabetes, to patients with new coronary pneumonia, it has also achieved unexpected effects. Judging from the experimental results, if Nigerians live in modern times, they may be more “preferred” by the coronavirus than Homo sapiens.
  In addition to causing these overt diseases, how does the Nepalese genes increase the risk of depression and other mental illnesses? In this regard, scientists explained that sunlight can reduce the risk of depression. However, in ancient times, Nepalese people lived in dark and dark caves for a long time. In order to adapt to such a low-light environment, they developed insensitivity to light. Gene. This gene will cause people to suffer from a skin disease called “actinic keratosis” when they are exposed to excessive light. Therefore, modern people with this gene must also live as far away from light as possible, which may increase The incidence of depression.
  The Nepalese heritage once helped Homo sapiens become stronger and live better, but the heritage from a distant period is no longer so adapted to the changes of the times. Will these “legacy” be passed on in the future?