This argument is akin to saying we're not "newer" apes ala
> The refutation is of the idea that it’s a strictly chronological ordering of species, with the old species still inside and intact. The correct view is that while homosapiens are indeed mostly "newer", the “older” apes were also modified throughout evolution
Obviously.
> As Paul MacLean (1964), originator of the triune-brain theory, stated,
>> man, it appears, has inherited essentially three brains. Frugal Nature in developing her paragon threw nothing away. The oldest of his brains is basically reptilian; the second has been inherited from lower mammals; and the third and newest brain is a late mammalian development which reaches a pinnacle in man and gives him his unique power of symbolic language.
And they quote other textbooks that are making claims along these lines too; this is right at the beginning of TFA. So I think you are wrong that “no one thinks that”.
Of course they don’t think the old brains are 100% static but there are claims that they are largely conserved.
That they're not static doesn't necessarily mean that they aren't largely conserved.
Importantly modern reptiles and humans have experienced the same amount of evolution. There’s vaguely similar traits, but we don’t call whale flippers hands because that’s what the structures was in some of their ancestors or even what it is in related species. Similarly we don’t call human hands flippers because that’s what the structure started out as even further back and it’s still preforming that function in modern fish.
The human visual cortex for example is larger than most creatures entire brain, it’s a wildly different structure than you find on a frog.
Every scientific model and analogy is flawed in some way, but many are still useful.
By noticing that while they have significant differences, those structures also have significant similarities, we were able to correctly answer one of the greatest questions of all time: where did humans come from?
Of all models, this one is particularly useful.
As I have mentioned before these structures are very different, compare the giant spheres used by snakes, bird, frog etc to process visual information and try and map that to a rodent, bat, or human. Hint you’re not going to be able to locate an obvious sphere because the fundamental morphology is just different.
Going back to your analogy saying visual cortex of frog is wildly different from a human visual cortex. That's similar to saying a frog backbone is wildly different from a human backbone. Sure that's true but there's also a shared common core functionality largely conserved across time
So yes frogs and humans both have a visual cortex, because we both have eyes. It really doesn’t explain anything beyond that point.
Frogs, birds, etc have very distinct spherical visual cortexes. Humans and squirrels don’t have that kind of spherical structure. So, other than naming where vision is processed the same thing the overlap isn’t particularly strong even at the most basic structural level.
It’s perfectly reasonable to extrapolate from studied organisms to species that share recent common ancestors. But reptiles don’t represent the probability distribution, they represent different results from that distribution under different evolutionary pressures. Extrapolation backwards and our common ancestor was very different from all decedents.
It would seem enough people did to warrant this person to write about the topic.
The correct view is that while the neocortex is indeed mostly new, the “older” more central structures were modified throughout evolution.