[Little Bill]

Rupp from U Chicago postulated that extinctions occurred on a regular basis and had a grad student study the problem. The thing that got my interest was a post by Blam on the Hiatus in the spread of civilization after the Sargonite Empire which lasted about 300 years.

They found a crater in Iraq that could have some impact on this hiatus but I never followed it up.

[RegulatorCountry]

Periodicity and near extinction level events would make sense of a lot of legend and certain religious prophecies.