Aerobic Cellular Respiration

No way would humans be able to function using just anaerobic cellular respiration. ATP molecules increase with oxygen in the Electron Transfer Cycle.   Our Aerobic cellular respiration cycle (including Krebs) needs oxygen; without it we would not survive... over long periods of time we would not be able to sustain our mass functions on only 2 ATP.   We use anaerobic cellular respiration all the time, such as during colder exercise processes.  If you take a look at our cold-blooded friends, they are often lazy and only prone to using quick bursts of energy infrequently... a snake can use the energy from a mouse over a long period of time, while that mouse eats 10% of its own body weight in food every day.