> Give a whale, dolphin, or orca some neuralink adapters for arms and dexterous hands, and a fully operational virtual human vocal apparatus, and they'd be able to match humans across a wide range of cognitive capabilities.

While I don't disbelieve this out of hand, I can think of different things that might easily make this untrue. On what evidence is this assertion based? Is it just "our brains are essentially similar and much of it is not hard wired therefore they should perform the same" or is there deeper science and/or testing behind this?

There's a lot of data that seems to fit. I'd say the science heavily leans this way - things like the dog/cat talking button studies, AI vocalization research in primates, whales, and birds, a whole ton of biological research across mammals, and most data start to paint a picture of mammalian brain structure being more important than particular quirks of human brain biology.

There are some theories of function out there, like that of Numenta, which seems consistent across mammal brains, and is at least partially explanatory of cognitive function at a cellular level. There's also value to be found in LLMs and AI research in understanding networks and recursion and what different properties of structures that perform different functions have to conform to.

Pilot whales and blue whales and some other species have upwards of 45B cortical neurons, and if higher cognitive function is conserved across species, then they'd have the potential to be significantly more intelligent than humans - all else being equal.

A useful thought experiment is to compare different species to feral humans. Absent culture, the training, education, knowledge, and framework for understanding reality, without language, natural and wild living is pretty grim and intense. There's a whole lot we take for granted underpinning our abilities to reach the heights of technology and abstract use of language and thought.

It could be humans and primates have some sort of magic sauce - a particular quirk of networking or neurochemistry that augments relative capabilities, as opposed to embodiment or other factors. People have sought the magic sauce for decades, however, and that doesn't seem to be a viable explanation.