What numbers are we looking at if we go back 10-20-30 or more generations in an individuals family history? If I have that many ancestors and all several billion people on the earth have the same, how is it possible to have that many people on the earth? I guess that some generations have collapsed in on themselves by incest but it seems like there can not be enough ancestors for all the people today. I guess I am confused.
Once you go back so far you have a certain number of grandparents but they aren’t all different people. Here’s a good explanation.