* * * What year is consanguinity?

The news soon aroused all kinds of voices of surprise and exclamation, from the secret of power to conspiracy theories. But if you think about it a little more, you will find it, which should be obvious. Let's make a simple estimate, regardless of the factors of intermarriage: a person has two parents and four grandparents. According to this calculation, N generations will have 2n ancestors. Based on the average generation of 20 years, 12 15 A modern American has 240 ancestors. How many ancestors do so many Americans have? Obviously, this is impossible, so in fact, almost everyone will almost certainly appear in different positions of the family tree many times as long as there is no heir later. It sounds ridiculous, but it's true. The above calculation is too rough, and more accurate quantitative mathematical conclusions will be calculated by probability theory. In 2004, the author of a paper found that even though there are strict immigration restrictions, such as only a very small proportion of people in each generation will immigrate to other regions, the same ancestors are not far away from us. After estimation and computer-aided verification, the same ancestor of * * * appeared not earlier than 1500 BC. What is interesting is further inference. Obviously, the ancestor of this "human ancestor" is of course our ancestor. Since then, the more people began to trace back, more and more * * * ancestors were there. Back to a certain moment, at that time, the ancestors of * * * will flood all mankind. This time point is called "the same ancestor point". According to the estimation of that paper, this time is about 5000 BC. At that time, everyone on the earth who was not completely extinct was the ancestor of everyone today. This sentence is very awkward and counterintuitive. It should be noted that all discussions about ancestors here take into account paternal and maternal lines. If only the paternal ancestors are defined as ancestors, the situation will be very different. In this case, genetic biology is a more effective tool, because everyone only gets the Y chromosome from his father. By sampling and analyzing human Y chromosome, geneticists can estimate the age of "* * * has ancestors". The latest research results show that it existed about140,000 years ago. He is generally referred to as "Y chromosome Adam" in the literature. This allusion can easily lead to some misunderstandings, as if Adam was the "first man" in human history. In fact, he was just an ordinary member of mankind at that time, but other men of his contemporaries cut off male descendants in the long river of history. The same analysis can also be used to estimate the closest maternal ancestors of human beings, and the genetic tool needed at this time is no longer chromosomes. This matriarchal ancestor is estimated to have appeared between 15000 and 250000 BC. She is called "Mitochondrial Eve". Unfortunately, she and Adam are strangers, separated by tens of thousands of years. Of course, these discussions are either based on the mathematical deduction of probability theory or on the assumption that the gene theory is not yet fully mature. However, it is quite interesting to just imagine the face of "the ancestor of all mankind" abstractly.