Sure they are—given that the placental clade contains most of the extant mammal diversity.
The very issue is that “mammal diversity” is vastly insufficient to make any conclusions about general independent evolutionary trends. The number of potential explanations of the advantages of intelligence derived from features from the recent common evolutionary origin completely overwhelms any evidence for general factors.
For one example, if someone were to demonstrate that intelligence is usually useful for a species of animals where the adults, by a quirk of evolution, have to take active care of their young for an extended time — BOOM. A huge quantity of the “independence” is blown up in favor of a single ancestral cause, the existence of nursing of the young in mammals. And the same happens every other time you can show intelligence specifically helps given an ancestrally-derived feature or is promoted by an ancestrally-derived feature in the whole group. The placental mammals are far, far too alike in life cycle, biochemistry, et cetera for parallel evolution within the group to be good evidence of real evolutionary independence of a trait on a scale of completely separate planetary biome evolutions.
The entire period from the cambrian explosion to now is what − 15% of the history of life?
That’s not disingenuity, that’s driving home the point. The octopus, separated by that whole stretch of 15%, is a far better case for evolutionary independence of intelligence than puttering around with various branches of the placental mammals — but still not nearly as good as if we had a non-animal example (or even better, a non-eukaryote). Unless and until we have good evidence of the probability of the evolution of animal-analogues, near-ape-level intelligence being (in general) weakly useful for animals (with Cephalopoda, Aves, and Mammalia being the only three classes we know have it or even strongly suspect from the fossil record have ever had it) is hardly strong evidence that near-ape-or-better intelligence is a highly probable feature of life-in-general.
The fact that brains increased by a factor of 2 to 3 orders of magnitude in 3 divergent branches of placentilia is evidence to me for robustness in selection for high intelligence.
Which is in error—I should have said “evidence indicating high intelligence is a robust developmental attractor”. As you point out, evolution rarely selects for high intelligence in individual lineages.
.. is hardly strong evidence that near-ape-or-better intelligence is a highly probable feature of life-in-general.
No, but this has become a digression. For the potential big picture galaxy models in consideration, we are more concerned with discerning between intelligence being highly improbable or only weakly improbable. The impact arising from the difference between weakly improbable and highly probable is relatively minuscule in comparison.
I am claiming only that the evidence for parallel development of intelligence on earth is sufficient to conclude that intelligence is in the vicinity of weakly improbable to probable, rather than highly improbable.
The very issue is that “mammal diversity” is vastly insufficient to make any conclusions about general independent evolutionary trends. The number of potential explanations of the advantages of intelligence derived from features from the recent common evolutionary origin completely overwhelms any evidence for general factors.
For one example, if someone were to demonstrate that intelligence is usually useful for a species of animals where the adults, by a quirk of evolution, have to take active care of their young for an extended time — BOOM. A huge quantity of the “independence” is blown up in favor of a single ancestral cause, the existence of nursing of the young in mammals. And the same happens every other time you can show intelligence specifically helps given an ancestrally-derived feature or is promoted by an ancestrally-derived feature in the whole group. The placental mammals are far, far too alike in life cycle, biochemistry, et cetera for parallel evolution within the group to be good evidence of real evolutionary independence of a trait on a scale of completely separate planetary biome evolutions.
That’s not disingenuity, that’s driving home the point. The octopus, separated by that whole stretch of 15%, is a far better case for evolutionary independence of intelligence than puttering around with various branches of the placental mammals — but still not nearly as good as if we had a non-animal example (or even better, a non-eukaryote). Unless and until we have good evidence of the probability of the evolution of animal-analogues, near-ape-level intelligence being (in general) weakly useful for animals (with Cephalopoda, Aves, and Mammalia being the only three classes we know have it or even strongly suspect from the fossil record have ever had it) is hardly strong evidence that near-ape-or-better intelligence is a highly probable feature of life-in-general.
Earlier, I said:
Which is in error—I should have said “evidence indicating high intelligence is a robust developmental attractor”. As you point out, evolution rarely selects for high intelligence in individual lineages.
No, but this has become a digression. For the potential big picture galaxy models in consideration, we are more concerned with discerning between intelligence being highly improbable or only weakly improbable. The impact arising from the difference between weakly improbable and highly probable is relatively minuscule in comparison.
I am claiming only that the evidence for parallel development of intelligence on earth is sufficient to conclude that intelligence is in the vicinity of weakly improbable to probable, rather than highly improbable.