A question about European History and common ancestry.

I've done a post on this previously. Once you look at the math, it actually makes perfect sense. The question was actually in regards to William the Conqueror, who is also pretty likely to be related to just about everyone of European ancestry, although maybe slightly less certain that Old Grandpa Charley, as we can call him.

Yes, but likely, so is everyone who has European descent.

Most likely, every white European can, with reasonable confidence, claim descent from William the Conquerer, and at that, any given Norseman who had descendants. William lived in the 11th century, so lets use 1063 for our start date. In genealogy, traditional calculations of generations use 25 years per generation. 2013 - 1063 = 950 years. Divided by 25 equals 38 generations.

This is important for two reasons. 32 Generations is the point where the number of theoretical ancestors in the 32nd generation (2^32 or 4,294,967,296) is larger than the number of base pairs (in the 3 billion range) in the human genome. In other words, 32 generations is the point where descent is (theoretically) statistically meaningless, and your genetic makeup is just as related to your ancestor as it would be to any random person you aren't descended from and was alive at that time.

It is important for a second reason because 2^38 equals 274,877,906,944. Yes, that is 275 Billion. That is the number of theoretical descendants of the old Bastard, assuming 2 children per generation (and for the record, he had ten known issue, so I'm being conservative in my estimates). Obviously, there is a LOT of closed loops there to account for the fact this number is orders of magnitude above the total number of people who have ever lived.

Even if we assume something like 90 percent of the lines go into dead ends before reaching modern times (which most genealogists wouldn't support anyways, if anything, it is the opposite), that's still 27,500,000,000 living descendants right now, so many times over what the current world population is.

So what is my point here? It is that you don't need to go very far back before claiming anything special about your ancestry becomes meaningless. Anyone who is of European ancestry is almost certainly descended from Charlemagne for instance, and probably William I as well. In fact, you can find estimates that place the most recent common ancestor of Europeans as having lived only 600 years ago (possibly a bit optimistic).

Now math is not exactly my forte, but if I visualize it correctly, if the population of the world is ~7 billion, and the theoretical descendants that this guy has now is 274,877,906,944, that is 40 theoretical descendants who should exist for every person currently alive. So if every person now alive can claim descent from him, they should, in theory, be able to trace back through 40 different paths, right?

If 1/10th of the world population is descended from him, the average descendant would be able to do it through 400 different paths! Aside from just being an interesting exercise in how closely we are related, this also relates back to the 32 generation cut off point. Because there are so many "closed loops", as I think of them, it means that that cut off point potentially gets pushed back.

Also, going back only a few more generations, to Charlemagne, we are getting into numbers in the trillions by the way.

Now anyways, to get back onto the topic, yes, as the Queen is a direct descendant of William the Conqueror, himself a descendant of the Norse, she would have ancestry of the Norse too, but as I pointed out, there are two huge asterisks. First, it is so far back as to be nearly genetically meaningless, as I pointed out. The second, and more important factor, is that what separates the Queen from everyone else of European descent isn't that she descended from these royal figures and that most people didn't, but rather than because of her specific line of descent being notable, we have the records of it still, while most people simply lack the written proof.

*Also, obviously, I do not take infidelity or adoption into account here, and take paternity at face value. If William kept getting cuckolded, and none of his kids were actually his, obviously none of this still applies.

Basically, the TL;DR is that exponential growth is really amazing, and you are probably married to your 23 x cousin three times removed.