As an estimate you can look at life expectancy before we used fossil fuels and compare them with after. Since fossil fuels are the foundation of all modern tec

As an estimate you can look at life expectancy before we used fossil fuels and compare them with after. Since fossil fuels are the foundation of all modern technology that changed that life expectancy, from plastics to fertiliser to most medicines. But Im sure, since fossil fuels like oil are now pretty much completely owned by China and Russia we may just get to find out what a world without them looks like, since neither are big on sharing right now.