system
Given the following post, respond as if you're commenting on Reddit:
human
[ELI5] What is the smallest number of people needed to repopulate the earth without inbreeding?

So you can't reproduce with immediate family, first or second cousins. 

Perhaps a diagram would help visualise this..

Edit: 

time frame is unnecessary.

No one in the first generation is related

Preferable conditions: e.g. No one dies at childbirth. 

I was thinking it could be as small as a few dozen...am I that wrong?
gpt
Well, you don't technically need to avoid incest, you just need to be careful to spread around as best you can.  A very un-ELI5 study showed that with optimal breeding, you could do it with as few as 32 people.  A more practical number is probably around 1000 breeding pairs.