It’s plausible that for both humans and orcas the relevant selection pressure mostly came from social dynamics, and it’s plausible that there were different environmental pressures.
Actually my guess would be that it’s because intelligence was environmentally adaptive, because my intuitive guess would be that group selection[1] is significant enough over long timescales which would disincentivize intelligence if it’s not already (almost) useful enough to warrant the metabolic cost, unless the species has a lot of slack.
So an important question is: How adaptive is high intelligence?
In general I would expect that selection pressure for intelligence was significantly stronger in humans, but maybe for orcas it was happening over a lot longer time window, so the result for orcas could still be more impressive.
From what I observed about orca behavior I’d perhaps say a lower bound of their intelligence might roughly be like human 15 year olds or so. So up to that level of intelligence there seem to be benefits that allow orcas to use more sophisticated hunting techniques.
But would it be useful for orcas to be significantly smarter than humans? My prior intuition would’ve been that probably not very much.
But I think observing the impressive orca brains mostly screens this off: I wouldn’t have expected orcas to evolve to be that smart, and I similarly strongly wouldn’t have expected them to have that impressive brains, and seeing their brains updates me that there had to be some selection pressure to produce that.
But the selection pressure for intelligence wouldn’t have needed to be that strong compared to humans for making the added intelligence worth the metabolic cost, because orcas are large and their neurons make up a much smaller share of their overall metabolic consumption. (EDIT: Actually (during some (long?) period of orca history) selection pressure for intelligence also would’ve needed to be stronger than selection pressure for other traits (e.g. making muscles more efficient or whatever).)
And that there is selection pressure is not totally implausible in hindsight:
Orcas hunt very collaboratively, and maybe there are added benefits from coordinating their attacks better. (Btw, orcas live in matrilines, and I’d guess that from an evolutionary perspective the key thing to look at is how well a matriline performs, not individuals, but not sure. So there would be high selection for within-matriline cooperation (and perhaps communication!).)
Some/(many?) Orca sub-species prey on other smart animals like dolphins or whales, and maybe orcas needed to be significantly smarter to be able to outwit the defensive mechanisms they learn to adapt.
But overall I know way too little about orca hunting techniques to be able to evaluate those.
ADDED 2024-11-29:
To my current (not at all very confident) knowledge, orcas split of from other still alive dolphin species 5-10million years ago (so sorta similar to humans—maybe slightly longer for orcas). So selection pressure must’ve been relatively strong I guess.
Btw, bottlenose dolphins (which have iirc 12.5 billion cortical neurons) are to orcas sorta like chimps are to humans. One could look how smart bottlenose dolphins are compared to chimps.
(There are other dolphin species (like pilot whales) which are probably smarter than bottlenose dolphins, but those aren’t studied more than orcas, whereas bottlenose dolphins are.)
A few more thoughts:
Actually my guess would be that it’s because intelligence was environmentally adaptive, because my intuitive guess would be that group selection[1] is significant enough over long timescales which would disincentivize intelligence if it’s not already (almost) useful enough to warrant the metabolic cost, unless the species has a lot of slack.
So an important question is: How adaptive is high intelligence?
In general I would expect that selection pressure for intelligence was significantly stronger in humans, but maybe for orcas it was happening over a lot longer time window, so the result for orcas could still be more impressive.
From what I observed about orca behavior I’d perhaps say a lower bound of their intelligence might roughly be like human 15 year olds or so. So up to that level of intelligence there seem to be benefits that allow orcas to use more sophisticated hunting techniques.
But would it be useful for orcas to be significantly smarter than humans? My prior intuition would’ve been that probably not very much.
But I think observing the impressive orca brains mostly screens this off: I wouldn’t have expected orcas to evolve to be that smart, and I similarly strongly wouldn’t have expected them to have that impressive brains, and seeing their brains updates me that there had to be some selection pressure to produce that.
But the selection pressure for intelligence wouldn’t have needed to be that strong compared to humans for making the added intelligence worth the metabolic cost, because orcas are large and their neurons make up a much smaller share of their overall metabolic consumption. (EDIT: Actually (during some (long?) period of orca history) selection pressure for intelligence also would’ve needed to be stronger than selection pressure for other traits (e.g. making muscles more efficient or whatever).)
And that there is selection pressure is not totally implausible in hindsight:
Orcas hunt very collaboratively, and maybe there are added benefits from coordinating their attacks better. (Btw, orcas live in matrilines, and I’d guess that from an evolutionary perspective the key thing to look at is how well a matriline performs, not individuals, but not sure. So there would be high selection for within-matriline cooperation (and perhaps communication!).)
Some/(many?) Orca sub-species prey on other smart animals like dolphins or whales, and maybe orcas needed to be significantly smarter to be able to outwit the defensive mechanisms they learn to adapt.
But overall I know way too little about orca hunting techniques to be able to evaluate those.
ADDED 2024-11-29:
To my current (not at all very confident) knowledge, orcas split of from other still alive dolphin species 5-10million years ago (so sorta similar to humans—maybe slightly longer for orcas). So selection pressure must’ve been relatively strong I guess.
Btw, bottlenose dolphins (which have iirc 12.5 billion cortical neurons) are to orcas sorta like chimps are to humans. One could look how smart bottlenose dolphins are compared to chimps.
(There are other dolphin species (like pilot whales) which are probably smarter than bottlenose dolphins, but those aren’t studied more than orcas, whereas bottlenose dolphins are.)
I mean group selection that could potentially be on a level of species where species go extinct. Please lmk if that’s actually called differently.