Er, a few species of placental mammal are hardly “widely separated lineages”. Trying to draw conclusions for completely alien biologies by looking at convergent evolution inside a clade with a single common ancestor in the last 2-or-3% of the history of life on Earth is absurd. And the fact that the Placentalia start with an unusually high EQ among vertebrates-as-a-whole make it a particularly unsuitable lineage for estimating the possibilities of independent evolution of high animal intelligence.
Perhaps that’s an argument for the difficulty of the chimp to human jump: we have (nearly) ape-level intelligence evolving multiple times, so it can’t be that hard, but most lineages plateaued there.
The conditions for the chimp to human jump require a series of changes where each brain increase enables better language/tools that pays for the increased costs.
Parrots/birds don’t seem to have a feasible path like that—light bodies designed for flight, lack of hands. Cetaceans can easily grow and support large brains but fire doesnt work under water and most tool potentials are limited. Elephants seem to be the most likely runner up, if primates weren’t around—perhaps in a few tens of millions or hundreds of years there could have been a pachyderm civilization.
So yeah—it might be somewhat rare, but its hard to say, as it didn’t take that long on earth.
Er, a few species of placental mammal are hardly “widely separated lineages”.
Sure they are—given that the placental clade contains most of the extant mammal diversity.
Trying to draw conclusions for completely alien biologies by looking at convergent evolution inside a clade with a single common ancestor in the last 2-or-3% of the history of life on Earth is absurd.
Hardly. Using the “last 2-or-3% of the history of life on Earth” is perhaps disingenuous, as evolution is highly nonlinear. The entire period from the cambrian explosion to now is what − 15% of the history of life?
More importantly—elephants, cetaceans and primates occupy widely diverse environments and niches.
And the fact that the Placentalia start with an unusually high EQ among vertebrates-as-a-whole
EQ is a rather poor indicator of intelligence compared to total synapse count.
The common placentilia ancestors are believed to be small rodent like insectivores which had small brains—presumably on the order of 21 million neurons in the cortex, similar to rats. 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.
Now of course, it’s fairly easy for evolution to just make a brain bigger. The difficulty is in scaling up the brain in the right way to actually increase intelligence. Rodent brains scale better than lizard brains, and elephant, cetecean, and primate brains scale even better still. So evolution found increasingly better scaling strategies over time, and in some occasions in parallel.
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.
Er, a few species of placental mammal are hardly “widely separated lineages”. Trying to draw conclusions for completely alien biologies by looking at convergent evolution inside a clade with a single common ancestor in the last 2-or-3% of the history of life on Earth is absurd. And the fact that the Placentalia start with an unusually high EQ among vertebrates-as-a-whole make it a particularly unsuitable lineage for estimating the possibilities of independent evolution of high animal intelligence.
Parrots and other birds seem to be about that intelligent, and octopi are close.
Perhaps that’s an argument for the difficulty of the chimp to human jump: we have (nearly) ape-level intelligence evolving multiple times, so it can’t be that hard, but most lineages plateaued there.
The conditions for the chimp to human jump require a series of changes where each brain increase enables better language/tools that pays for the increased costs.
Parrots/birds don’t seem to have a feasible path like that—light bodies designed for flight, lack of hands. Cetaceans can easily grow and support large brains but fire doesnt work under water and most tool potentials are limited. Elephants seem to be the most likely runner up, if primates weren’t around—perhaps in a few tens of millions or hundreds of years there could have been a pachyderm civilization.
So yeah—it might be somewhat rare, but its hard to say, as it didn’t take that long on earth.
Sure they are—given that the placental clade contains most of the extant mammal diversity.
Hardly. Using the “last 2-or-3% of the history of life on Earth” is perhaps disingenuous, as evolution is highly nonlinear. The entire period from the cambrian explosion to now is what − 15% of the history of life?
More importantly—elephants, cetaceans and primates occupy widely diverse environments and niches.
EQ is a rather poor indicator of intelligence compared to total synapse count.
The common placentilia ancestors are believed to be small rodent like insectivores which had small brains—presumably on the order of 21 million neurons in the cortex, similar to rats. 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.
Now of course, it’s fairly easy for evolution to just make a brain bigger. The difficulty is in scaling up the brain in the right way to actually increase intelligence. Rodent brains scale better than lizard brains, and elephant, cetecean, and primate brains scale even better still. So evolution found increasingly better scaling strategies over time, and in some occasions in parallel.
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.