That’s assuming that the human population is well-mixed; it should be obvious that e.g. aboriginal Australians and native Americans will not have a common ancestor that close by
For example suppose you have two containers filled with elastically colliding particles. Over an arbitrarily long time you can say that each particle has surely collided with every other particle, however if each container is closed then clearly particles from one container will not have collided with those from the other container over any amount of time
For example suppose you have two containers filled with elastically colliding particles. Over an arbitrarily long time you can say that each particle has surely collided with every other particle, however if each container is closed then clearly particles from one container will not have collided with those from the other container over any amount of time