I HAVE TO plug Suzana Herculano-houzel’s book “the human advantage” and all the research she and her group have done since it was published.
Short version: as you scale up a generic vertebrate brain, it only has 4x as many neurons every time it increases in mass by a factor of 10. (A factor of 16 after 100, etc). There are two clades that break this relationship: primates and birds, both of which have a 1:1 relationship between brain size and neuron number. The primate density is about the density of a mouse brain, and bird brains are 6x as dense as this. A large primate brain is much more impressive than a large generic-mammal brain. You get that elephants have brains about as impressive as chimps, and big whales have brains as impressive as late homo erectus—both of which I think make sense. Humans show up as having 4x the neurons of chimps/elephants and ~2x that of the biggest whales.
Human brains also appear to just be scaled-up primate brains, with the size of every brain region falling RIGHT on the trendlines of every other primate. I am skeptical of our subspecies being significantly smarter in any general way than other hominids with similar brain sizes.
Interesting. That table lists the methods that were used to get the neuron number; the method I trust most is the isotropic fractionator, it was explicitly designed to get around issues that had plagued neuron counts for a very long time using other methods. Most of the large whale numbers come from ‘optical fractionators’ instead.
Note the ‘false killer whale’ cortical neuron number—it lists two numbers from two methods, and the number from the isotropic fractionator is one third that of the optical fractionator.
I remembered reading about this a while back and updating on it, but I’d forgotten about it. I definitely think this is relevant, so I’m glad you mentioned it—thanks!
I HAVE TO plug Suzana Herculano-houzel’s book “the human advantage” and all the research she and her group have done since it was published.
Short version: as you scale up a generic vertebrate brain, it only has 4x as many neurons every time it increases in mass by a factor of 10. (A factor of 16 after 100, etc). There are two clades that break this relationship: primates and birds, both of which have a 1:1 relationship between brain size and neuron number. The primate density is about the density of a mouse brain, and bird brains are 6x as dense as this. A large primate brain is much more impressive than a large generic-mammal brain. You get that elephants have brains about as impressive as chimps, and big whales have brains as impressive as late homo erectus—both of which I think make sense. Humans show up as having 4x the neurons of chimps/elephants and ~2x that of the biggest whales.
Human brains also appear to just be scaled-up primate brains, with the size of every brain region falling RIGHT on the trendlines of every other primate. I am skeptical of our subspecies being significantly smarter in any general way than other hominids with similar brain sizes.
Wikipedia lists several whales with more cerebral neurons than humans.
Interesting. That table lists the methods that were used to get the neuron number; the method I trust most is the isotropic fractionator, it was explicitly designed to get around issues that had plagued neuron counts for a very long time using other methods. Most of the large whale numbers come from ‘optical fractionators’ instead.
Note the ‘false killer whale’ cortical neuron number—it lists two numbers from two methods, and the number from the isotropic fractionator is one third that of the optical fractionator.
I remembered reading about this a while back and updating on it, but I’d forgotten about it. I definitely think this is relevant, so I’m glad you mentioned it—thanks!