Mark Liberman at Language Log asks this question, spurred by a Chinese professor’s claim to be a 73rd-generation descendant of Confucius. His conclusion: well, yeah, but if anyone in China is descended from Confucius (and this is documented), probably everyone in China is. Given a long enough time this would be true with “China” replaced by “the world”, but it probably hasn’t been long enough.
Are we all descended from Confucius?
Published
God plays dice 
The paper “On the Common Ancestors of All Living Humans” suggests “model of recent human history which suggests that the common ancestor of everyone alive today very likely lived between 2,000 and 5,000 years ago.”