Okay, suppose I want to get an estimate of the number of decdendents a person after a period of time.
Say a man has two childern, and those two childern have an average of two childern each(and I know people used to have more childern the that, but a lot of those died as well). So two living childern who then grow up to have their own childern. Say each of those childern procreate around the age of 20 on average(I’m assuming here that people used to have kids more or less around that age for a long time, if not earlier. 20 seems decently midrange).
Then extraporlate over 1000 years(say 1000 AD to 2000 AD), probably for a person of Europeon descent.
I’m not sure how to correctly calculate this to get a fairly correct range assuming
1 generation per 20 years over 1000 years, with 2 childern to each generation.
I know the resulting number will likely be lower, so if somewhat wants to supply more accurate numbers for averages. I just want a decent low-end estimate.
Each generation will have twice as many descendants as the previous. Since each generation takes 20 years to procreate, take our 1000 year period and divide it in to fifty 20 year intervals. That means the generation in 1000 years will have 2^50 = 1,125,899,906,842,624 descendants in it (a bit over 1 quadrillion). The total number of descendants throughout the entire 1000 year period will be 2^51 - 1 = 2,251,799,813,685,247.
These figures are obviously way too high, as they do not take into account “inbreeding”. I’m not sure exactly how it should be adjusted to take that into account, however.