Ellen asked me this morning what Ancestors meant (a word mentioned on NPR when I was not listening and was caught off guard on the context). I naturally answered --- "It is your parents, grandparents and so on". The discussion then morphed into DNA, biological etc. Then I made the global comment - "We are related if you go back far enough".
So now the statistician pops in ----- The human species is more than 40 generations old - so 2^40th or 10 trillion would be the total possible ancestors. However it is estimated that only 106 Billion people have ever lived (Carl Haub - 2002) but that number is based on some specific assumptions - birth mortality, life expectancy etc.
So at point are you and I connected? - what generational pair from one to 40? Hard to imagine the genealogy chart with 40 tree diagrams with stories of multiple marriages, partners, name changes, etc. Assuming only the "direct pairs" by the 10th generation you have 2046 "biological parental ancestors".
Kin, Clan, Tribe, Ethnicity, Nationality, - we are forever "grouping" --- creating a network. I like Susan's answer on the Census survey -