This is interesting:
According to Portland State University anthropologist Cameron Smith, any such starship would have to carry a minimum of 10,000 people to secure the success of the endeavor. And a starting population of 40,000 would be even better, in case a large percentage of the population died during during the journey.
I don't know why you assume a single starship. Was the New World colonized by one huge friggin' ship crammed full of genetically diverse colonists? Couldn't waves of colony ships over years and decades provide the genetic diversity?
I don't know why, if we can't send waves of ships, you assume that you couldn't achieve genetic diversity with a large stock of fertilized eggs (assuming the use-by date is sufficiently far off) to be used on the way and once there.
I thought I remembered a relevant blog post on this subject. And I found it.
I don't know why it is that high given that Earth itself has gotten to over 7 billion with a far less promising genetic bottle neck:
Turns out, somewhere between 130,000 to 190,000 years ago, the human species was reduced to less than 1000 breeding individuals--just a few thousand people in total.
So a thousand, then? Assuming all are breeding individuals.
I suppose we could gain experience with colonies within our solar system. Or even in orbit or on the Moon. We're probably getting ahead of ourselves, no?
Of course, these are all uncertain calculations, anyway.
And it assumes the colonists don't wipe each other out at some point. We think we are unique in societal self destruction capacity, with nuclear weapons. But thousands of years ago when humanity was in city-states or small bands, hand weapons and fire could wipe out entire civilizations.
So, regardless of how many we need genetically, spread those colonists out to keep them from easily attacking each other early on (but close enough to inter-breed).
