So what does major extinction mean exactly? Here is a list to help you understand a little better.
1) In the Permian–Triassic extinction event, which they deal with in the manuscript cited above, 90 to 96 % of all species died.
2) In the Cretaceous–Paleogene extinction event 75 % of all species died.
3) In the Triassic–Jurassic extinction event 75 % of all species died.
4) In the Late Devonian extinction 70 % of all species died.
5) In the Ordovician–Silurian extinction event 60 to 70 % of all species died.
Does this mean that god made 5 major screw ups? I say 5 major screw ups, as their have also been minor extinction events (i.e. Aptian extinction) which surely mean god made more than these 5 screw ups. It surely then logically follows that either god is a colossal prick, or he screwed up which does not fit well with infallibility and omnipotence.
Luckily this line of reasoning only holds if you believe in the existence of a god, if not then you can live life rationally and just accept your fragile existence and appreciate it for what it is...........Amazing.