The model I have devised has CO2, CH4, O2 and Insolation in balance, the primary function of evolution in the biosphere has been to influence the composition of the atmosphere. Because of this even small unbalances of the ratio of atmospheric gases can have momentous consequences. NEVERTHELESS the principle function of human intelligence has been to overcome the ice ages. ICE AGES have been an anomoly, continental ice sheets amplify negative temperature trends due to ALBEDO, and rapid fluctuations of 10 degC have been evident over the last 400,000 years. If a small but continuous trend in CO2 output by Homo Sapiens over the last 50,000 yrs has been able to rebalance the thermal budget of the earth, and negated the effect of ALBEDO, then it folows that human civilisation can flourish, the follow on effects due to advanced intelligence, have led to
1. The neolithic farming revolution
2. Early Civilisations
4. The Industrial revolution
5. The scientific revolution.
THE INITIAL CONDITIONS which allowed humans to overcome nature gave us a brain that allowed us to develop modern society and science.