Intelligence has evolved on Earth at least three times - mammals, corvids, and octopuses. All the mammals have roughly the same brain architecture. But the corvids are not on the same evolutionary branch, and have a different neuron design and a different brain architecture. "Such behavioral flexibility might seem unexpected because a layered cerebral cortex, the highest integration center in the mammalian brain, is not existant in birds."[1] So there's more than one way to do intelligence. Useful to know for AI purposes.

Octopuses have a much more distributed system than mammals, suggesting a quite different approach is possible.

[1] https://niederlab.org/Nieder%20(2017)%20COBS.pdf

You left off Parrots, which are just about as intelligent as Corvids. For example, keas have a similar number of pallial neurons to ravens (or maybe slightly more). Parrots and songbirds generally have extremely high neural density but still lower raw neuron counts compared to primates, which makes their competitiveness in many cognitive tasks interesting.

Among parrots, everyone knows African Greys but cockatoos are also highly intelligent, with goffin's cockatoos the standouts in terms of cleverness.

I don't think you can single out corvids from the rest of the avians and at the same time bunch all mammals together. I don't think there's evidence that their smarts or brain architecture are qualitatively different from other birds, some of which are plenty smart. If intelligence - for some definition of intelligence - evolved separately in mammals and birds, it's not implausible to me that the basic architecture developed before avian dinosaurs branched from other theropods, and some theropods might have been quite smart indeed.

Bird brains are interesting because they've dealt with a significant chunk of the energy intensity of mammalian brains. Octopus brains are interesting because brains are traditionally energy intensive and top predators are usually long lived. Octopuses have this energy intensive sunk cost but also have a short lifespan.

I wish I understood enough of the appropriate level of neuroscience to get a bit of an understanding of the similarities and differences between bird and other brains.

Adrian Tchaikovsky explores each of these kinds of intelligence across his sci-fi Children of Time trilogy.

Can we count mammals and corvids separately if their common ancestor was already set on the path to intelligence? The amazing book Other Minds by Peter Godfrey Smith hinges it's argument on minds evolving twice, on the fact that the common ancestor of humans and octopi was probably a simple worm-like creature that had little or nothing in the way of a brain or consciousness.

I have to imagine that corvids and mammals had a common ancestor with more working brain structure. Though maybe you can make the case that "intelligence" showing up later on isn't the same thing as simply having a brain.

But it's much more impressive to me that there's convergent evolution from brainless to brain-having, than from brains to intelligent brains. Don't get me wrong, it's still awesome but doesn't feel like an out of nowhere path for natural selection to take.

like Siglip, Dino and LFM :D