In the case of primates, we only evolved manipulating appendages after our brains evolved a use for them. If the dolphins had an understanding of their environment as profound as primates, they'd grasp its malleability, and over time (again, astronomical time scales and all), may come to evolve some kind of manipulatory capability.
That's not true at all. Primates had manipulators long before "their brains evolved a use for them" (if by "evolved a use for them" you mean sapience).
Great apes make wide use of tools.
Tool use is present in all four non-human great apes. Other examples include making nests and sharpening sticks with which to kill monkeys. Humans are more dextrous than other apes- but there are other reasons for this as well- the human hand is freed of a locomotory use.
Tool use is also present in less related primate species:
Furthermore even the most basal of primate species (such as lemurs and tarsiers) possess manipulators:
Organisms do not evolve things based on their "understanding of the world". Evolution in this case as in all cases is driven by random mutation and natural selection, what kind of understanding of the malleability of the environment around them the dolphins have make no difference.
Furthermore astronomical timescales are not anything special to evolutionary processes (since these are the timescales over which such processes take place) and do not magically circumvent the very basic limitations in evolution and biology. These limitations are the reason why we don't have lions with prehensile tails coming out of their heads, or quadrupedal birds, or crocodillian launch vehicles, etc.
Having a manipulator and evolving a better manipulator/better dexterity over time is a totally different thing to having no manipulator at all and magically evolving it out of nowhere.
Even if there is some possibility of such organisms developing useful manipulators, it is still fairly improbable. And even then there is no guarantee that they would develop further, because of the other factors involved.
I certainly don't "adhere" to it. I'm just pointing it out, as I currently believe it to be somewhat less wrong than your beliefs.
I never said anything about
you adhering to it, just about the proponents of the idea in general.
The problem is it is a great deal more wrong than my beliefs, the reasons for which I have already stated.
