After 3000 years, all people will have a common ancestor living today.

If we take the average number of children 2, then through N generations the number of descendants of a person is 2 ^ N. It would seem that everything is simple - a common ancestor of 7 billion earthlings lived 33 generations ago ((log (70,000,000,000)) / (log (2))), that is, about 800-1000 years ago. However, this formula is valid only if the entire population of the Earth is accidentally crossed.

In reality, as everyone knows, crossing occurs mainly in isolated groups, with relatively rare intergroup crossings. Therefore, the common ancestor of humanity lived much earlier than 800 years ago. DNA analysis and computer modeling suggest that he lived from 2,000 to 5,000 years ago . The most interesting thing is that this law is extrapolated to the future.

In the future, the process of crossing the human population will be more random due to globalization. But even by a pessimistic estimate, it turns out that after about 3000 years every inhabitant of the Earth will be a direct descendant of every living person . Of course, only those living people who continue the genetic line are meant: leave children, whose children leave children, and so on. According to evolutionary biologists , a dead end genetic line of 35 generations ago had about 20% of the population. Now, probably much more .
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It should also be understood that a common relative does not mean total DNA, because the number of chromosomes is still limited.

Conclusion 1. Having given birth to a child, you become the ancestor of all mankind.

Conclusion 2. Every single person is part of a global system for transferring DNA from the past to the future. No one has unique genes, all unique genomes "dissolve" in a common pot. Your genes will be transferred from the past to the future without your help.