Most Recent Common Ancestor

I just ran across this article, which I believe someone had mentioned previously by reference to an article that talked about it. I am a bit of a math nerd so reading the actual article and its modeling assumptions is quite interesting.

It is amazing to think that the most recent common ancestor of ALL human beings may have lived as late as 2000 years ago. Perhaps more surprising is the fact that all people who lived just 2000 or 3000 years before that are either (1) the ancestors of EVERYONE on earth today; or (2) have no descendants living today.

http://tedlab.mit.edu/~dr/Papers/Rohde-MRCA-two.pdf

I suppose we should not be surprised that we are finding so many common ancetors among ourselves 200 or 300 years back.