We’re all related to dead people

So, I’ve been meaning to check out the new on-line only science magazine, Nautilus, and finally did so yesterday after a link from wonkblog.  Very cool post about the relatedness and lack thereof of human beings.   (Also, love the visual layout of Nautilus– about as appealing as any website I’ve come across).  Additionally, M.S., despite being an NC resident, wrote to tell me he’s tired of bashing the legislature and he wants more epigenetics.  Well, this isn’t quite epigenetics, but its genetics:

 In 2004, statistician Joseph Chang, computer scientist Douglas Rohde, and writer Steve Olson used a computer model of human genetics to show that anyone who was alive 2,000-3,000 years ago is either the ancestor of everyone who’s now alive, or no one at all. Think about that: If a person alive in 1,000 BCE has any descendants alive today, they have all of us—even people from different continents and isolated populations. This line of thought led to the revelation that everyone of European heritage alive today is a descendant of Charlemagne, who ruled over much of Europe as the first Holy Roman Emperor. As science writer Carl Zimmer wrote last week, it’s “Charlemagne for everyone!” …

It doesn’t get any less weird when you look at it from the other angle: While you more than likely have four distinct grandparents and eight distinct great-grandparents, past a certain number of generations back, your number of ancestors stops growing exponentially, because they start being the same people. By the time a couple who married in 1450 in Holland, has had a few hundred descendants over the span of several generations, those people are distantly related enough that some of them start marrying (and, yes, reproducing with) each other. That couple thus becomes the however-many-great-grandparents of the children of those unions along multiple branches of their family tree. (If your number of ancestors actually doubled every generation, by the time you counted back the 40 or so generations to Charlemagne, you’d have around a trillion ancestors. Scholars estimate the world population was only about 300 million at that point.) Stretch this back a few thousand years and you can see how you wind up being related to every other member of your species.

That’s just fascinating stuff.  I suspect these are some factoids that people who know me well are going to get sick of hearing about.  And, I’ll have to start bragging about my great, great….great grandfather Charlemagne.

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About Steve Greene
Professor of Political Science at NC State http://faculty.chass.ncsu.edu/shgreene

2 Responses to We’re all related to dead people

  1. Jason says:

    Thanks for sharing– you’re right, completely fascinating, and not at all what I would have guessed. Although I’m a little annoyed at you for leading me to another interesting website (Nautilus) that will come between me and any productivity for the next hour!

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