How small can a humanoid creature get and still retain human-level intelligence? Specifically, what would be the smallest brain possible capable of advanced reasoning and what brain-body mass ratio would be reasonable at such scales.

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    $\begingroup$ Biology still does not know, how could we? $\endgroup$
    – Mołot
    Jan 25, 2017 at 22:08
  • $\begingroup$ What @Mołot said, but: people have been known to survive and function with large parts of their brains destroyed or disabled. The smallest normal brain ever recorded weighed ~1.1 kg. Brain size is not as important as cortical area (i. e. the total surface of brain "folds"). That's no answer, but it may help. $\endgroup$
    – pablodf76
    Jan 25, 2017 at 22:31
  • $\begingroup$ Well, parrots can be quite intelligent - see the famous example of Alex the African Grey. But as with many other points of their physiology, flying creatures are under a lot of evolutionary pressure to minimize weight, which probably wouldn't be the case with non-fliers. $\endgroup$
    – jamesqf
    Jan 25, 2017 at 22:33

2 Answers 2


Intelligence seems to be related to how wrinkly a brain is, maybe more so than brain size, or brain body-mass (although presumably these are also factors). All the animals we think of as intelligent have wrinkly brains.

The more wrinkles (or folds) the more neurons are packed into the same-size skull. It may be possible to enhance the (potential) intelligence of an existing species by increasing their brain folds genetically.


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Who says there is a limit? Nature evolves for the environment you are in, an example of this is recent studies suggest some birds like ravens (that can make tools to get food) and some parrots that can mimic human voice are just as intelligent as monkeys, but we can not measure the intelligence in the same way as you would a bird vs monkey.

Nature has developed intelligence based on what the creature needs to survive.

With brain to body mass our current interpretation may be wrong as bird brains are developed differently to our human and even monkey brains but they can reason.

Ravens have been seen to drop nuts on pedestrian crossings and waiting for the cars to smash the hard nut shells and when the cars stop moving the birds swoop down and get the nuts.

Ravens have been observed leading wolves to injured animals so the wolves can kill the animal and they both share the food.


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