The Younger Dryas Impact Hypothesis proposes that a comet airburst approximately 12,800 years ago triggered the Younger Dryas cooling period, megafaunal extinctions, and civilizational disruption, promoted by researchers including Firestone et al. (2007) and Powell (2022), though contested by Holliday et al. (2023). The hypothesis remains majority-rejected in mainstream science due to irreproducibility issues and a 2021 key paper being retracted for image manipulation—importantly, this does not imply the existence of lost advanced civilizations.
Firestone et al., PNAS (2007); Powell, Science Progress (2022); Holliday et al. refutation (2023)