Rezwan wrote: I was told about a brilliant book relating to longevity, evolution, etc. Nick Lane’s Oxygen: The Molecule that made the world.
Apparently, oxygen enables predators.
Oxygen enables predators just because it allows creatures to grow to be sufficiently large size to be predators. Without oxygen organism size is single cell or perhaps just a few cells. And similarly higher oxygen concentration allows larger body size and higher metabolic rates in those organisms which do exist.