I am posting the following spontaneous IM yawp at the request of Rog:
[10:37] Heatkernel:* yeah, man the proterozoic era
[10:37] Heatkernel: that was the real party time
[10:37] Heatkernel: for the microbes
[10:37] Heatkernel: I’ve been reading about that in Margulis
(* “Heatkernel” substituted for actual IM screen name).