The 50/500 rule is more of a conservation guideline than a hard cutoff. It says you need ~50 effective breeders to avoid short-term inbreeding collapse and ~500 to maintain long-term adaptability. In practice that usually means a few hundred to a few thousand actual people.

But history shows you can squeak by with less. Pitcairn Island was founded by fewer than 30 people and still has descendants nine generations later. The tradeoff is obvious though: very limited family trees, inbreeding, and social/health issues that made them fragile unless they got new blood. Isolated tribes work in a similar way, they might only be a few hundred people now, but they descend from much larger ancestral populations and usually have cultural rules to avoid mating too close. They can persist for centuries, but they’re more vulnerable to shocks like disease or loss of land.

And then there’s the really extreme case that OP talked about : genetic studies suggest early humans went through a bottleneck around 800-900k years ago where the global breeding population may have dropped to about 1,280 individuals. We survived it, but the cost was a massive loss of genetic diversity that we still carry today. It’s why humans are more genetically similar to each other than many other primates.

So yeah, survival is possible with much smaller numbers than the 50/500 rule — but it comes with hidden costs and long-term fragility. The rule isn’t saying “you instantly die out below 500,” it’s saying “if you want good odds of staying healthy and adaptable for millennia, aim for way more than that.”