On the Common Ancestors of All Living Humans (2003) [pdf]
tedlab.mit.edu
tedlab.mit.edu
It's safe to say at this point that humans are far more genetically diverse than previously thought and we may not share a single common ancestor considering that some groups contain large amounts of denisovan AND/OR neanderthal DNA that is non-existent in other groups.
It's also irrelevant to the MRCA of extant humans.
Again, not saying it is or isn't wrong, just that orders of magnitude more is known about this now than was known in 2003.