Relativity and the presidents

BridgeAnne d’Avignon, then a 7th-grader from California, did some solid genealogical digging back in 2012 and showed that all but one U.S. president is a descendant of King John, best known as the monarch who was forced to sign the Magna Carta in 1215. Some have taken this to be evidence of the hidden hand of the real powerbrokers at work, even claiming it means “all USA presidents are preselected.” Perhaps that’s so, but sharing an ancestor from eight hundred years ago is not proof of such a conspiracy.

For every generation you go back in your ancestry, the number of ancestors in that generation doubles.

For every generation you go back in your ancestry, your number of ancestors doubles. Two, four, eight, sixteen, and so on. By the time you get back twenty generations you have over a million 18th-great-grandparents. At thirty generations you have over a billion 28th-great-grandparents. Thirty generations back is about eight hundred years ago, give or take. There’s just one little problem, the population of the entire world at that time was less than half a billion.

When people who are related, even very distantly, have children together the result for genealogists is what is called pedigree collapse.

So you are filling out your tree chart with ancestors for great-grandma and great-grandpa Barnes, but they were first cousins. In their tree every generation from their common grandparents back has all the names filling two spaces. Even if they were third cousins, or fifth cousins, twice removed, like Franklin and Eleanor Roosevelt, eventually the number of unique ancestors is reduced by those individuals who take up more than one spot in the family tree. When people who are related, even very distantly, have children together the result for genealogists is what is called pedigree collapse. AKC registered dogs have very well documented pedigrees, a requirement to prove a ‘purebred’ is just that. Click here to view a diagram of the ancestry of a border collie that consists of just six 18th-great-grandparents. As noted above, there should be a lot more than that.

Someone now living could theoretically be descended from every single one of those Englanders of eight hundred years ago who still have descendants around today.

What does that have to do with all of the presidents(except little Dutch boy Martin Van Buren) being the offspring of King John? Well, if the population of the entire world in 1215 was less than half of the number of ancestors that an individual living now should have had, if they were all unique individuals, there must necessarily be a whole lot of pedigree collapse. There were roughly two and a quarter million people living in England at that time. Someone now living could theoretically be descended from every single one of those Englanders of eight hundred years ago who still have descendants around today.

16 million men living today are direct male-line descendants of Genghis Khan.

It might be helpful to look at it another way. Genghis Khan founded the Mongol Empire which at it’s height extended in a broad swathe from the Pacific into Europe. The Khans remained powerful for generations and left numerous male descendants, both legitimate and illegitimate, everywhere they went. DNA studies of the Y chromosome that is passed down from father to son indicate that roughly 16 million men living today are direct male-line descendants of Genghis Khan. This figure does not account for any descendants of the Khans who are female or any of their descendants, a number that must be many times larger.

Every US president, save one, has had significant amounts of English ancestry. Queen Elizabeth II descends from King John several times over, and nearly everyone else in England who isn’t of recent immigrant stock probably is as well. We should be surprised that any US president is not descended from British Royalty, except of course for Martin Van Buren, whose ancestry is Dutch. In fact, it is a virtual certainty for any of us that have ancestors who lived under a monarchy are descended from a royal family. We are all princes and princesses.