Eli5: how are humans, who are two legged, able to out endure creatures that are four legged?
It is a combination of evolution and muscle composition. Generally the animal kingdom has species which have evolved muscles for super fast bursts, and others which have evolved to sustain moderate workload over long periods. With almost all being capable of both to a certain extent. Humans are certainly capable of short burst high intensity work, but are much more adept at long duration work. This allowed us to be much better hunters. It is more beneficial to be able to outlast virtually any prey than to be the fastest over a short distance. Also as it relates to your specific question, operating on two legs requires far less energy than using four, so it is much more sustainable over long periods.
What? When did man outrun a tiger?
Humans (and the dogs we have taught to do it with us) are the only animals that run long distance. All other creatures settle into a comfortable jog that eats up miles without over tiring them. Dogs run better below 40°F, from 40-70 F it’s roughly equal, above 70F humans do better, and markedly so above 80F. Four legged critters aren’t meant to run distance, they’re meant to sprint.
It’s because most animals are completely incapable of running in an aerobic state, which allows us to fuel our muscles with the oxygen we breathe, so we don’t run out of energy. When we sprint (and the only way most animals can run), it’s anaerobic, which uses energy stored in the muscles, and there’s a finite reserve of those.
Imagine an ultra long distance race between a slower solar powered dune buggy and a faster gas guzzler. Eventually the car will run out of gas and the dune buggy will catch up. Then it’s game over.
– Running on two legs is more efficient over long distances than running on four legs
– Humans have the best cooling system of all mammals (sweating), so we don’t overheat as easily as our prey.
– Humans can carry water with them, so they can stay hydrated for longer.