system
Given the following post, respond as if you're commenting on Reddit:
human
How many Homo Sapien ancestors do I have (approximately)?

I have 2 parents + 4 grandparents + 8 great-grandparents + ....

This is a pretty broad Fermi question, but I was wondering if anyone could take a whack at it, and what assumptions they would make.  Some things to consider:

* What is your bin-size?
You could use the average lifespan for our entire species over its entire history for all areas of the world, or you could use the average age over every 5000 years on each continent, etc.

* What do you assume about my ancestors continental migrations (out of Africa)?
I am of Western European descent (only applicable if you separate average lifespan by geographic area).  

* What do you assume about inbreeding?  
How far back would you go until the number of ancestors per generation starts to shrink, rather than increase by a factor of 2?  Do your inbreeding assumptions conform to your geographical bin-size (inbreeding in Europe vs. Africa)?

* Do you take into account possible non- Homo Sapien ancestors (Neanderthal) ?

If any more clarification is needed, let me know.  I realize the answer will probably be a range of orders of magnitude.
gpt
Funny thing about that. If you just use the simple geometric progression — you, parents, grandparents, great-grandparents and so on — when you get to 37 generations, you've exceeded the total number of human beings who are estimated to have ever lived in the entire history of the universe. That's about a thousand years.