Normal for Norfolk

This story reminds me of the ancestor game, as described by Brad de Long.

It works like this. The number of ancestors you have doubles every generation; two parents, four grandparents and so on.

So, how many ancestors did you have 1000 years ago? If we assume a generation lasts 25 years, this is 40 generations ago, so the answer is 2 to the power 40.

This is 1099 billion*.

Trouble is, 1000 years ago, the world’s population was only just over 250 million.

Go figure, if you can.

* If this calculation is wrong, there’s an obvious reason why.

Note to American readers – Norfolk is our equivalent of Alabama.

Comments

[spencer]

What you are doing is just the same as the stock market rule that it takes a larger percent increase to offset a small percent drop. If a stocks goes from 100 to 50 it is a 50% drop. But to get back to 100 the stock has to increase 100%.

The percents are different depending on what way you approach the calculation because you are working from a different base.

[john]

There is a simple answer to this paradox, (it's only simple because I just read it in a biology book). The huge number of ancestors generated in the calculation is arrived at because it assumes that all of your ancestors are unrelated individuals. In practice we are an incestuous species, maybe not at the mother/son father/daughter level, but certainly when it comes to cousins and other "more removed" relatives. When this factor is allowed for a more realistic picture emerges.

[Jackalope]

In taking personal genealogy back to the reasonably-reliable royal genealogies of the Early and High Middle Ages, I've noticed that the same kings and princes appear repeatedly, all over one's genealogy, and often considerably divided in generations. Ethelred the Unready might be both one's 34th and 39th great-grandfather, and everything in-between.