It seems reasonable to assume that any earlier iterations of a global civilization would also have relied heavily on the burning of coal and oil for energy, at

It seems reasonable to assume that any earlier iterations of a global civilization would also have relied heavily on the burning of coal and oil for energy, at least for a while. And yet there has been no spike in atmospheric CO2 concentration in the last 400,000 years like the one we have now: http://www.geocraft.com/WVFossils/last_400k_yrs.html http://www.geocraft.com/WVFossils/last_400k_yrs.html