>>212481505 (OP)>(...)Go back just eight generations ... and already there are over 250 people on whose timely couplings your existence depends. Continue further, to the time of Shakespeare ... and you have no fewer than 16,384 ancestors ...At twenty generations ago, the number of people procreating on your behalf has risen to 1,048,576. Five generations before that, and there are no fewer than 33,554,432 men and women on whose devoted couplings our existence depends. By thirty generations ago, your total number of forebears - remember, these aren't cousins and aunts and other incidental relatives, but only parents and parents of parents in a line leading ineluctably to you - is over one billion (1,073,741,824, to be precise). If you go back sixty-four generations, to the time of the Romans, the number of people on whose cooperative efforts your eventual existence depends has risen to approximately 1,000,000,000,000,000,000, which is several thousand times the total number of people who have ever lived. Clearly something has gone wrong with our math here. The answer, it may interest you to learn, is that your line is not pure. You couldn't be here without a little incest - actually quite a lot of incest - albeit at a genetically discreet remove.
from bill's bryson "a short history of nearly everything"