Of course it is going on today. One of the differences is that the Earth does not have almost totally anaerobic organisms as it did in the formative years. One of the differences is that those organisms did not have the reserves of organic carbon to burn like man is doing. We are changing the dynamics of the atmosphere.<quoted text>
And what makes you think that those changes would not continue to happen. Your own post proves that CO2 was once higher than it is now and yet life not only continued but flourished during that period. The organisms that converted the CO2 into O2 and organic carbon are still here and still converting as they have for millions of years.
There is little doubt that the Earth will continue to flourish until the Sun cycles out. However, mankind is more interested in his own species survival as a species.