In considering the composition of atmospheric gases as corroborative evidence for such an increase in gravity (and noting the nature of the course of such changes), the relative mass of the atmosphere as a whole is immaterial. The issue is whether an increase in g may have favoured the incorporation of heavier gases like CO2 and O2 into carboniferous biomass or mineral oxides as the function of their molecular weights, conversely allowing lighter gases and H2O to escape into the atmosphere through displacement. This is clearly a difficult and contentious point, but it warrants proper reasoned scientific consideration, rather than the puerile repudiation of the entire sense of the question by those who seem not to have understood it; and indeed to have responded rather dismally by viciously down-voting it under the cloak of privilege.

Possibly I might have framed the question differently, or even asked separate questions had I not been perhaps naively encouraged by the belief that those purporting to be scientists at this site would be capable of accommodating several related lines of inquiry simultaneously, and of responding to a well-considered question asked in good faith with proper diligence.