Doesn’t mean this is what I think happened, but sounds just as plausible as comets causing havoc to me.
In the end IMO this field has been greatly disserviced by Hancock. The yDIH just as well might have been the correct explanation but this guy won’t stop yapping about aliens alongside the same. So the “establishment” academics seem to be very wary of this hypothesis and being associated with him. Now it’s clear that’s dumb of the academics as well, they should be logical and choose the correct hypothesis no matter what flavor it associates them with. Sad that one of the likely most important times of human history has become so contentious due to human emotion and ego coming in the way of scientific rigor.