How is it that nearly 20% of all Asians are related to Ghengis Khan? I feel like they mean the mongols, but every article I read says Khan.

Question

How is it that nearly 20% of all Asians are related to Ghengis Khan? I feel like they mean the mongols, but every article I read says Khan.

In: 1751

Answer 1

As you may know, you have two parents and most likely have 4 grandparents, 8 great grandparents, 16 great-greats, 32 great-greatgreats…

If you keep doubling, then by 20 generation you will have about a million ancestors. Around 1200 A.D. is about 32 generations ago, so if you always had unique ancestors, you would have 4,294,967,296. As you may know, there weren’t that many people on the planet at that time, let alone in a region of the planet.

So what happens is that the ancestors’ tree collapses as people marry their cousins.

Now, on the other side of the equation, let’s say you had 2 children and they had 2 children and your grandchildren had 2 children. Then, in 32 generations, you would have 4,294,967,296 descendants related to you.

So it’s not really surprising that ghensis khan is related to so many people. What is surprising is that so many living people carry the same Y chromosome that he had. He wasn’t the first person to have that unique variant of y chromosome, but he was pretty close to when that y chromosome showed up. To have that many direct male descendants is much more surprising because it’s very easy for male lines (or female lines) to end.

It’s easier to see with last names. China has the oldest history with last names and, at one point, had about 12,000 different names; today, only a quarter of them are still in use. So that means 3/4 of the names didn’t have a male heir to continue the name. Although with last names, there can be more artificial factors, for example, sometimes families will change name based on emperor or simplify them. But the majority are gone because there weren’t male heirs. Also, what tends to happen if there is no artificial naming is that a few names become the dominant names. For example, the top 10 surnames are shared by 42.9% of the population. This is called Galton–Watson process if you want to look up more about it