Wondering if evolution could have stopped at monkeys is like wondering if there's a button that can reset the ecosystem with one press. Evolution will keep selecting for organisms which is able to collect the most negative entropy and dissipate it all - if not humans then it would have been something else that would cause a huge pollution event.
Earth once did not have much oxygen - Oxygen was in fact toxic to most life forms in Earth's early days. One life form produced oxygen as a byproduct. It spread all over the planet, produced a lot of oxygen, and caused what we call an extinction event.
Earth once did not have much oxygen - Oxygen was in fact toxic to most life forms in Earth's early days. One life form produced oxygen as a byproduct. It spread all over the planet, produced a lot of oxygen, and caused what we call an extinction event.