“In 1980, Luis Alvarez and a group of other scientists discovered evidence for the extinction of the dinosaurs by a huge impact event which researchers eventually linked to a hidden crater on the Yucatan Peninsula. Before their research, no one had found a strong connection between impacts and extinctions. Not long after that, in 1984, Paul Raup and Jack Sepkoski proposed that the dinosaur extinction was only one of about ten large extinctions that seemed to follow a regularly recurring pattern at about 26-million-year intervals.
Of the ten, the largest occurred about 65, 210, 245, 364, and 440 million years ago … the one 245 million years ago was particularly catastrophic; an incredible 90 percent of all life disappeared from the planet.” (Extract from ‘The cycle of cosmic catastrophes’ by Firestone, West and Warwick-Smith on mass extinctions.)
A more recent extinction was only 2 million years ago (refer Benitez and colleagues in the above book). It might be linked to supernovae. However, “ Supernovae are one of the several mechanisms that can produce extinctions … “
“ We do not believe or suggest that just the supernova or just the impacts caused the extinctions of the megafauna – it was more complicated than that. Some percentage of plants or animals perished from each of the following causes, although some are more important than others:
• Supernova radiation, both directly and through genetic damage
• High-velocity supernova particle bombardment
• Impact blast wave and heat
• Impact-related flying debris
• Fires, both directly and through destruction of the food supply
• Toxic chemicals and heavy metals in the air and water
• Event-related climate changes, directly and by destruction of the food supply (chill theory)
• Epidemics induced by radiation and by ecosystem destruction (ill theory)
• predators, both human and animal, that hunted the surviving animals(overkill theory) “
The most recent extinction was only 13,000 years ago!