The earth's carrying capacity before fossil fuels was far, far lower than the 7 billion current population, especially with current living standards.
The only reason we can support that many is because of a complex web of economics that causes the earth to produce far more food than it otherwise could, and then enables distribution of that food to where the people are.
Without fossil fuels, we couldn't even produce the fertilizer needed to support the food. You could argue that there is some alternative set of lifestyles that would enable to eliminate fossil fuels without asking 90% of the population to die, but that would similarly require some sort of top-down totalitarian regime in order to get there and keep us there.
At this point, we do need the energy. The only way to maybe not need it would be to somehow put a global version of Stalin in a position of absolute power.
Failing to understand just how critical energy is to any sort of non-apocalyptic future is one of the biggest dangers in our current political debate about what should come next.
