Two studies published in the latest issue of Science have revealed that birds, reptiles, and mammals have developed complex brain circuits independently, despite sharing a common ancestor. These findings challenge the traditional view of brain evolution and demonstrate that, while comparable brain functions exist among these groups, embryonic formation mechanisms and cell types have followed divergent evolutionary trajectories.
It makes sense, when you look at other amniotes.
Sure, reptiles* show some signs of intelligence. Crocodiles use tools, monitor lizards recognise human faces, etc., those are all signs of cognitive capabilities. But it’s simply not on the same level as your typical mammal or bird; it’s like comparing a strawberry to a jackfruit, you know?
And yet, if these advanced cognitive capabilities we see in birds and mammals were inherited from their common ancestor, we’d see them in reptiles too.
*by “reptiles” I mean the paraphyletic group composed of the extant members of the clade Sauropsida, minus the nested clade Aves.