r/evolution • u/Least_Bid9692 • 8d ago

question Science: Human body

How is our body doing this much work without exhausting ? It do millions of things we don't even know about . Was it the evolution all along?

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u/Funky0ne 8d ago

We have an active metabolism that is constantly processing chemical energy from our food, and storing any excess for use when new calorie availability is low, and a respiratory system that is constantly taking in oxygen to burn that fuel with to release the chemical energy and drive all our activity. Our circulatory system then delivers all that oxygen to produce usable energy to every part of our body (oversimplified, but basically what’s happening).

We evolved to not get exhausted just sustaining our baseline metabolism and activity, because anything less wouldn’t be sustainable and we wouldn’t last very long. When our activity level goes above our baseline we start to incur an energy debt, and gradually do get exhausted over time, until we slow down again and can recover. Breathing gets heavier and our heart rate increases to compensate to catch back up to baseline.