I came across this article which states that brain takes about 20% of the body's energy. This is quite a lot compared to its size. Somewhere I read that even if this is a lot, this must be an absolute requirement otherwise by the theory of evolution, such high energy requirement brains would already have been eliminated.

My question is we know evolution is never stationary, so what is the recent trend (last 4000-5000 years) in the usage of brain energy? To me only 2 cases are possible (in an evolutionary stable sense):

  • We are evolving to require less brain power for the same functionality, but the size of functionality remains same (i.e. we are able to think the same thing with same power requirement).
  • We are evolving to require more brain power for the same functionality, but the size of functionalities increase(i.e. we are now able to think the bigger things but the power requirement increases).

I might be wrong in the above 2 statements or it may seem redundant, but I am drawing parallels to IC's here in a broader sense.

Also can these generalisations be extended to the evolution of animal brain also?

Any kind of speculative answer based on logic would also be nice.

  • $\begingroup$ This question may be answerable from the context of evolution of modern humans vs earlier humans, or in the context of evolution from common ape ancestors, but how exactly do you expect to measure brain energy use from someone 4000 years ago? $\endgroup$
    – Bryan Krause
    Commented Aug 31, 2018 at 18:06
  • $\begingroup$ @BryanKrause I don't know maybe modern technology could do it? I have no idea $\endgroup$
    – DuttaA
    Commented Aug 31, 2018 at 18:20
  • $\begingroup$ @BryanKrause on second thoughts it seems that their really is no way of measuring brain activity in ancient times but can we not measure from atleast 10000 years back from genetic data $\endgroup$
    – DuttaA
    Commented Sep 1, 2018 at 4:56
  • $\begingroup$ Could intracranial space provide a basis to measure energy consumption? $\endgroup$
    – youzer
    Commented Apr 5, 2019 at 14:25
  • 1
    $\begingroup$ There was a widely publicized paper suggesting that human brains shrank around 3000 years ago, presumably as a result of outsourcing brain functions to society and technology, but this finding has been challenged since as invalid. $\endgroup$
    – Arnon Weinberg
    Commented Nov 30, 2022 at 5:10


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