Regardless, prokaryotes lacked the ability to tolerate the oxygen that they (as cyanobacteria) produced. This crushing limit lasted for billions of years, unti

Regardless, prokaryotes lacked the ability to tolerate the oxygen that they (as cyanobacteria) produced. This crushing limit lasted for billions of years, until the age of eukaryotes. This step is as much of a mystery as the Cambrian Explosion.