If you believe this study, the entire human race was reduced to a population of something like 2,000 people about 70,000 years ago. The near-extinction of humanity was, it is suggested, caused by a massive drought. That’s a pretty dramatic story.
Makes me wonder. If we did suffer a massive kill-off of people (like, say, if the Cylons attacked) what would be the smallest population size necessary, assuming an equal number of men and women, to create a viable gene pool? I’ve not the time right now to look around for the answer to that question but it’s obviously one of great importance for the 39,000 or so surviving colonists searching for a home called Earth.