After an adrenaline rush, why do humans experience a sudden severe drop in energy? Would this not be disadvantageous for primitive survival?
In: Biology
In addition to what people discussed, a long lasting “fight or flight” rush would actually be evolutionarily harmful. The fancy term for what you are describing is the sympathetic nervous system. This is what gives the boost. A byproduct however is the shutdown of the parasympathetic nervous system (which is responsible for digesting and rest). [Side note: there is a lot of fabulous research on the role of these nervous systems in PTSD. People with PTSD experience longer and more frequent sympathetic response and shorter, less effective parasympathetic responses].
Now while the sympathetic system is rushing, one of the parts of the brain who’s function is reduced is the frontal lobe. This is because your body is more worried about senses and perceptions (and responding to that input) then decision making, planning, or worrying about consequences. Let’s take an example of our ancestors being attacked by a bear:
Individual A: sympathetic system activates, blood rushes to muscles to either fight the bear or run from the bear. Once the immediate threat is reduced (i.e. gained distance from bear) speed is not as important and now tactics take over. Person A climbs a tree, hides somewhere, remembers what to do in case of bear attack. Higher chance of survival.
Individual B: sympathetic system activates but this time doesn’t turn off in time. This person keeps running (or fighting). Odds of beating a bear in an endurance match are pretty slim. Lower chance of survival.
These bursts are designed to buy us enough time to figure out the problem rather than solve the problem themselves. Now, could a long enough sympathetic response help us fight off a bear? It’s possible. But evolutionarily, survival depended on humans ability to outsmart the bear. Keep in mind, if you run from the bear then your sympathetic will activate, but the bear’s probably will not (chasing after someone is not really a strong flight or fight response). But attacking the bear will activate your sympathetic system AND the bear’s. This means everyone gets stronger, faster, and dumber. Humans lose their only advantage.
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