I googled the amount of people that lived on earth throughout its entire history, it’s roughly 108 billions. If I take 1 person and multiply by 2 for each generation of ancestors, at the 37th generation it already outnumbers that 108 billions. (it’s 137 billions). If we take 20 years for 1 generation, it’s only 740 years by the 37th generation.
How??
(I suck at math, I recounted it like 20 times, got that 137 billions at 37th, 38th and 39th generation, so forgive me if it’s not actually at 37th, but it’s still no more than 800 years back in history)
In: 1391
The simple answer is: the family “tree” isn’t actually a tree. Many of the 138 billion you mention are actually the same persons, those “slots” overlap.
In reality, you have, say, a billion people on Earth. They intermingle, randomly, maybe not too incestuously and all a bit simplified, to create a new generation of a billion. Those again do the thing. On and on. But the population doesn’t increase in this scenario. How? Because quite soon, there will be someone who’s mother **and** father share a common ancestor; quite a lot of such people, actually.
Put differently: ever heard of statements such as “everyone is related to (or even descended from) [insert famous figure from 2000 years ago here]?” That in return also means that both your father and mother are related to that person, so somewhere long back their heritages meet.
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