Birds have developed complex brains independently from mammals

If brains developed twice independently here on earth, then…

The actual paper says it’s just a part of the brain opposed to the whole organ.

> 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.

They didn't show those 'complex brain circuits' were not present in common ancestor. Am I missing something and this is well known? There is also nothing about fish. I suspect such complex organisms cannot exist without "excitatory and inhibitory neurons" the article talks about.

mammals are x86, birds are ARM

And birds are at 2nm process nodes while mammals are 22nm

Scale is all you need.