In Dawkin's book "The Selfish Gene", he discusses genetic relationships in family lines (e.g., your genetic similarity is 1/2 that of one of your parents, 1/4 of your grandparents, etc.). He mentioned that going back only a few generations, your genetic similarity to your family line is no different to than it is to the rest of the population.* At what point is that genetic similarity reached? In other words, what is my genetic similarity to the average human genome? In other other words, how many great-great-greats do I need to trace back before my ancestor is no different than a total stranger? * Making extensive genealogy somewhat pointless?