From first principles, it seems surprising that a blow to the head would cause unconsciousness rather than just impaired function.

I've heard a lot of analogies to computers -- "Your brain has to reboot." But computers reboot when there is an error because they are explicitly designed to do so, in order to recover and prevent further damage.

So, did we evolve the capacity to get knocked out for similar reasons -- because it helped us recover or prevent further damage? Or is the capacity to get knocked out just an "accident" or an inevitable consequence of the way our brains are designed, without a good evolutionary explanation?

(I realize the answer might be: "we don't know". In that case, I'd wonder what the prevailing opinions are and what if anything we've ruled out).

  • $\begingroup$ peripheral nerves also do this, when touched (eg in surgery) they completely stop working for some time $\endgroup$ May 20, 2017 at 16:07
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    $\begingroup$ It is worth noting a blow to the head causes unconsciousness by doing enough damage to the brain to disrupt its function, a knockout is a concussion. This is why knocking someone out is actually very difficult and very risky. The movie knockout is a myth. We did not evolve to be knocked any more than we evolved to go into cardiac arrest. $\endgroup$
    – John
    May 21, 2017 at 17:47

1 Answer 1



We did not evolve in order to become knocked out. See the wikipedia link. The "water" in the head is designed to not make us get knocked out that easily. However each dampening system has a limit.


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