io9 has an article about how there are only so many common ancestors that we can all have that’s very interesting and a fun thing to think about. Also interesting is the discussion on most recent common ancestor for the world.
From the article “Why humans are all much more related than you think“:
When we get right down to it, we must face the truth that we’re all hopelessly inbred. It’s a question of basic mathematics – there simply aren’t enough ancestors to go around. To understand what I mean, let’s say you were born in 1975, your parents were both born in 1950, your four grandparents were born in 1925, your eight great-grandparents in 1900, and so on. In other words, your number of ancestors doubles every 25 years the further back in time you go.
If you take this back just 1,000 years, you’ll find that you have well over 500 billion ancestors in a single generation. Considering there’s fewer than seven billion people on this planet – and even that is far, far more than any other point in human history – there’s something seriously wrong here. The solution, of course, is that you don’t have 500 billion distinct ancestors, but rather a much, much smaller number of ancestors reappear over and over and over again in your family tree.
Things like this always bring to mind my own experiences with this sort of thing. One of my friends when I was a child was a Backus whose family was from upstate New York–just like my Backus family (though I haven’t established a link, since we have fallen out of contact). My two best friends (who are sisters) are also my 10th cousins via John Dodge (b 1636, d 1711). My boyfriend is my 10th cousin once removed via John Howland (which my boyfriend doesn’t like to think about). And, with all the fervor over the royal wedding right now, via Thomas Ford (b abt 1591, d 1676) I am the 12th cousin once removed of Prince William, with whom I also attended university (which is also where I met my 10th cousin best friend, and which is a few miles from Dundee, where some of my Irish ancestors lived before emigrating to the US).
It is fascinating the ways in which we are all related, but what I also find interesting is the where–how locations allow for the meeting of these now disparate groups to come together.