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Cat’s will also literally try to clean you as well!

There are more mites specialized to live on your eyebrows skin than many like to think about. =3

Yes! Cooperation seems to be just as fundamental, if not more, than competition. We wouldn't have gotten volcanic islands to break down into soil if it weren't for the partnership that is lichen. We wouldn't be able to digest a tenth of what we're able to eat if it weren't for our gut bacteria. We wouldn't have trees if it weren't for mycorrhizal fungi which over 90% of plants depend on.

There's a famous paper/framework called "Major evolutionary transitions in individuality" that sketches out a big picture pattern of major evolutionary advances in complexity following a surprisingly consistent pattern: As cooperation and division of labor strongly increase, selection starts working on larger entities. This pattern holds all the way back to the origin of life itself as things moved from self-assembling molecules to compartmentalized populations of molecules, from replicators to chromosomes, from RNA+enzymes to DNA+proteins, from prokaryotic cells to eukaryotic cells, from unicellular to multicellular, from individuals to colonies/superorganisms, and (possibly) onwards to more complex societies

https://www.pnas.org/doi/10.1073/pnas.1421402112

mmmm it's equally likely that mitochondria's precursors were self interested parasites or predators, whose negative effects were competitively neutralized by defensive host adaptations that exploititively colonialized them. No intelligence or cooperation is required for co-opt-ation to evolve. It's a straightforward consequence of game theory.

This is a frustrating response to my comment. I am aware that symbiosis is universal. That's not what I'm talking about. I am talking about the specific and highly unusual behavior of crawling inside of a much larger animal's mouth and trusting it not to eat you. Cleaner fish are highly intelligent[1] and it appears that this intelligence is necessary for their niche:

- picking a good location for a cleaning station requires long-term planning and real strategic judgment;

- deciding which hosts to accept is a complex skill requiring some sort of rudimentary theory of mind + long-term development of social ties;

- like crows, cleaner fish are jerks who constantly try to screw each other over, so there is something of a cognition arms race.

I will add that the wrasse family of cleaner fish use rocks to smash open shellfish (i.e. they are tool-users), and they have very complex group strategies for raising their young. In fact I'm not convinced that wrasse evolved to be cleaner fish at all: they are natural scavengers and scum-suckers, perhaps cleaning stations are a form of cultural technology.

I would be extremely surprised if any of this was true for cone ants. I suspect that is more hard-wired, perhaps a local subspecies stumbled into a genetic fluke, and as you say due to game theory it is a local optimum this population has settled on. If this behavior were common like it is in vertebrates, we probably would have seen it earlier. But who knows? 20 years ago I would have thought "fish have a form of culture" is too ridiculous an idea to consider.

[1] Seriously: https://journals.library.columbia.edu/index.php/cusj/blog/vi... https://www.nature.com/articles/s41598-025-25837-0