Thursday, January 05, 2006

More on Caesar

My previous entry left me thinking about the likelihood of being a descendant of Julius Caesar. For example, my boss, of noble birth and a long recorded genealogy, is a descendant of Charlemagne at least in two different lines, but because it is impossible to follow the blood line during the first turbulent millennium, I have to resort to probability estimates.

Caesar had two children, Julia and Caesarion, who later became Ptolemaios 15, king of Egypt, and a stepson Gaius Octavius, who later became Augustus Caesar. Undoubtably Caesar had many secret relationships, also heterosexual ones, and we can hereby presume that his genes have had better than average chances of replicating. If at 50 B.C. the world population was roughly 200 million, we can assume that at least two of them were descended of Julius Caesar.

We assume descedants of Caesar are equally productive to non-descendants. The only way to produce a non-descendant is that both parents are non-descendants. If we denote with P(i) the probability that a random person i generations after Caesar is not his descendant, then P(i+1) = P(i)^2, which simplifies into P(i) = P(0)^(2^i). After some numerics, we see that in 23 generations, or around 500 A.D. nearly half of the world population would be descended from Caesar, and by today practically everybody.

Of course this is hardly quite correct, because some populations live in such physical and cultural separation that descendency may not have reached them before the 19'th century. Even we Finns are considered somewhat isolated, but by no means entirely and in any case two millenia is ample of time for some traveling warrior, trader, or priest to seed some of my ancestors.

Ok, so do I now feel any Caesareity? Nope, not even the slightest foretelling sting in my torso. And by the way, it was Shakespeare who put the words "Et tu, Brute" in Caesar's mouth. Suetonius claims Caesar's last words to have been "You too, my son" in Greek. Some sources also claim that he cried "This is violence!" (in Latin) when stabbed for the first time, but perhaps during over 20 stabs you have time to think of a more eloquent last words.


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