The mass extinctions that occurred 250 million years ago and 65 million years ago may have been due to gradual process or?

The mass extinction that took place 250 million years ago and 65 million years ago was due to the catastrophic activities that took place at that time.The extinction almost 95% of the population took place due to major climatic change that took place long time ago (250 million years ago).The extinction of dinosaurs took place 65 million years ago due to the activity of the meteorites that suddenly hit the earth and killed almost all the dinosaurs.Both of the event took place due to gradual process or catastrophic activities.

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.