Dolphins are intelligent and live in groups. In my world, there is a magical way to cook food that would be possible underwater. Given that increased calorie availability, could cetaceans evolve a human-level intelligence and appendages suitable for tool use?

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    $\begingroup$ Technically, in a fictional world, everything is evolutionary possible; including dolphins' transition into otters and then evolving brain/humanoid form/whatever you want. But if you're science-based, you would need to depict conditions that favored each of the (major) shifts for the source animal to become target humanoid. And in this case you'll get better results taking an animal closer to target, since whatever env that prefers animals having certain abilities would act pretty uniformly on all animals subject to that env, thus those that have to change less would just evolve faster. $\endgroup$
    – Vesper
    Apr 18 at 13:07
  • $\begingroup$ Everything is evolutionarily possible with enough time and tampering. 👽 $\endgroup$
    – Mentalist
    Apr 19 at 5:10
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    $\begingroup$ Cetaceans were originally terrestrial mammals. So just select another starting species that already had some of your desired traits before becoming a marine species: en.wikipedia.org/wiki/Aquatic_ape_hypothesis Just because it might not have happened in our world, there’s no reason it couldn’t in yours. $\endgroup$ Apr 19 at 5:53
  • $\begingroup$ Not directly to the question, but check out: en.wikipedia.org/wiki/Startide_Rising $\endgroup$
    – Yorik
    Apr 19 at 21:16
  • $\begingroup$ More seriously, although I have heard the argument that increased calorie intake can help evolve intelligence, I do not believe that is scientifically accurate. An individual may benefit intellectually in their own lifetime, but this does not change there own genes, so it is not part of evolution. However, potential mates might start to find more intelligent dolphins more attractive than good hunters, when there is ample food and hunting skills are less important and this will direct evolution in the more intelligent direction. $\endgroup$
    – KDP
    Apr 20 at 3:12

4 Answers 4


Intelligence: yes

If dolphins would get some advantage in using that "magic" by virtue of their brains, evolving it to better employ that magic would likely have a corresponding effect of increasing their general "IQ" making abstract thinking available to them. Your magic essentially allows those wielders to spend less time hunting for the same food availability, thus having some free time might also cause their brains to divert attention to tasks not directly linked to survival, like planning ahead, allowing them to find a way to outsmart the natural selection instead of fighting against it like non-intelligent animals do. Thus I say that magic-using dolphins will acquire or evolve intelligence.

Appendages: no

There is an issue with those appendages, namely, they need to be used to evolve, and dolphins have already evolved their front appendages into fins, which display a set of finger-like bones inside, indicating that they have sometimes been on the surface. The ability to grab tools is essentially lost on the dolphins, because the main use of front appendages for human ancestors was to grab (already!), in process of climbing trees and thus resisting gravity, favoring strong and long appendages that were easy enough to employ for grabbing something movable. Dolphins do not have evolutionary pressure towards requiring them to grab or push the unmovable objects, and instead have pressure towards swimming better, so evolving grabbers would cause them to swim weaker and die out.

Using tools at all: maybe

After all, it's us humans are those that use tools by grabbing them with our hands; crows have been using their beak and legs to hold stuff, some other creatures use mouth to move stuff around (mostly offspring tho, like big cats), so an intelligent creature would eventually find a way to use whatever devices their body has to attempt to perform the required action. Thus, dolphins might start using their mouths to grab, hold and eventually handle bones and stuff made out of them (later wood, if any exists underwater in your world, or anyway it could still get washed into the sea), and given enough time, material and intellectual desire, they could start creating and using tools that are usable by them while held in the mouth. Past this point, the society of them could start seeing those specimen that use tools better as "better" for evolution, providing selection biases for any mutations that involve better tool handling with mouth (for example, a long back-side tooth or a weird set of teeth that exactly helps a dolphin to control lateral tool movement without shifting their head - nature is VERY weird when it comes to helping constructs), thus future generations might adapt their facial appearance to using tools somehow.

But, since you have some "magic" in operation, there is another possibility which I think is more likely to happen if the world is left to evolve without author's attention, namely, that those dolphins would start using magic as tools replacement, thus escaping the need of using exact tools altogether. Say, if they need to break something, they just use magic to overheat a crucial part of that something, and it falls apart, no tools needed. Say they need to ward off a predator - heat some water right behind yourself, or directly the predator's nose, and watch it fly from the unknown. Etc.

  • $\begingroup$ If telekinetic magic is available, they might also develop tool use while using their magic for the fine motoric control. That could be more energy efficient than direct application of magic. $\endgroup$
    – Gloweye
    Apr 19 at 12:17

Dolfins do not have opposable thumbs, and that poses a limitation to the handling ability, and with that to the increase of brain capability.

Additionally, proto-humans could free up their hands thanks to the erect position. Something similar is unlikely to happen for dolphins, as they need their fins for swimming.

A better candidate would probably be an otter: they have already good manipulation abilities.


Fine manipulation for tool use and development is the hurdle

Cetaceans are already quite intelligent, and given an environment that encouraged tool use, intelligence is likely to be selected for on some level. They're not at human-level in the real world, but the gap is narrow enough that that's not a real concern for plausibility.

The main problem is that intelligence won't be selected for if it can't be applied effectively, and as far as we know, that means it coevolves with tool development use, which requires some degree of fine manipulation as well.

Obviously their fins are spoken for, and their mouth isn't going to scale to handle fine manipulation, but there is a weird solution available to half the dolphin population: Their penises. Dolphins penises are prehensile and surprisingly dexterous. While they're not adequate for tool use at their present stage of development, they're the closest thing to a grasping appendage for fine manipulation any cetacean has, and could conceivably form the basis for fine manipulation work in an evolved dolphin. Their mouths could still contribute, carrying objects when fine manipulation isn't needed, the penis handles the tricky stuff.

No, I don't think it likely, but it's the closest you could plausibly get starting from a cetacean body plan without tens of millions of years of evolutionary "work".

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    $\begingroup$ If the penis was useful outside of reproduction, there's nothing stopping female dolphins evolving pseudo-penises - maybe kinda like the ones in hyena? $\endgroup$ Apr 19 at 9:16
  • $\begingroup$ @JackAidley: True. We all grow the same parts, they just get (wildly) repurposed depending on the sex chromosome/hormonal levels during development. Evolutionary paths that enhance functionality in males can, by side-effect, lead to the trait spilling over into the opposite gender (there's a term for this I'm forgetting, where a trait that harms the reproductive fitness of women who have it nevertheless does well because it helps their male offspring more than it hurts the women). If that spillover ends up beneficial, rather than harmful, it could eventually develop the trait in females. $\endgroup$ Apr 19 at 15:30

Frame Challenge:

Why go with humanoid cetaceans, if making cetacean humanoids would be easier? The evolutionary path from a hominid ape into a semi-aquatic lifeform with cetacean-like features is easier and more plausible than dolphins suddenly regaining terrestrial features.

When vertebrates first crawled out of the water, it was an optimal evolutionary move, that increased their chances of survival. When vertebrates then evolved back to be aquatic through "cetaceanisation" (reptiles into ichtiosaurs, then mammals into cetaceans) it was also a beneficial move.

But there is no immediate gain for cetaceans to regain the apendages and body plan required to evolve into humanoids: the middle steps towards that are sub-optimal.

The other way around? Sure. There is no reason why a coastal subspecies of Australopithecus could not evolve adaptations to live a semi-aquatic life, which would make it appear slightly cetacean-like. Hairless body, protective layer of blubber, webbed hands and feet, sealable nostrils moving closer to the forehead, expanded lungs, no earlobes...all of those are easy adaptations, that would not hinder the hominid on land much, but would be very useful underwater.

The question is: WHY? Why would apes evolve to be semi-aquatic? My suggestion is, strand the species on a small continent, or better yet, archipelago of islands that are slowly sinking, or being overtaken by an ice sheet. This would slowly move the biosphere underwater, making surviving on land difficult. Ultimately, these water-apes would need to evolve towards the same external properties as otters, seals or sealions, and ultimately cetaceans, just to chase the vanishing calories. But the thing is, there is no plausible way to evolve from a hominid skeleton to a cetacean skeleton, because the midway forms would be all but useless. So the outcome would be a semi-aquatic creature that looks like someone stretched the features of a small porpoise on a human skeleton.


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