As for what might explain the near-extinction humanity apparently once experienced, perhaps another kind of catastrophe, such as disease, hit the species. It may also be possible that such a disaster never happened in the first place — genetic research suggests modern humans descend from a single population of a few thousand survivors of a calamity, but another possible explanation is that modern humans descend from a few groups that left Africa at different times.
-It's unlikely that the Toba catastrophe was the root cause of the bottleneck as reasoned in this investigation:
-It's unlikely that the Toba catastrophe was the root cause of the bottleneck as reasoned in this investigation:
https://www.livescience.com/29130-toba-supervolcano-effects....
- I wonder if the hypothesis of leaving Africa in small groups could be effectively tested.