Larry Niven's "Known Universe" (KU) features "The Outsiders" as one of its most prominent alien races.

As per KU canon, the Outsiders evolved in a frigid moon (similar to Nereida) and they sustain themselves by generating electricity via thermal differentials, placing one part of their bodies in frigid darkness and another on a light source (thus creating a thermal differential). An "Outsider" is in essence a living thermocouple.

In an infinite universe everything is possible I guess, and in a fictional world, "my rules" rule.

However, I try to consider the feasibility of such an evolutionary approach. How could one put some rigor into the development and evolution of such an species, that it could lever such a metabolic approach to evolve not just life, not even complex life, but sentient life (which I'd think is a very metabolic intensive process.)

Any ideas how I (or one) would go about that? Suggestions?

Obviously, there'll be some hand waving and suspension of disbelief, but I'd like to see/use some hard science into this.

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    $\begingroup$ So the catabolism would come from a thermoelectric effect, and anabolism would be what exactly? Are these aliens substantially different than humans or do they simply derive the energy for catabolism differently? $\endgroup$ – Rob Apr 24 at 16:45
  • $\begingroup$ That's what I'm trying to conjure. Niven's novels never quite got into those details. The evolution of such an alien life-form is just taken as-is. The novels are great btw, but I've always asked myself "ok, how would this really work?" $\endgroup$ – luis.espinal Apr 24 at 18:44
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    $\begingroup$ It isn't obvious to me that it is possible to make something unicellular that would be able to use thermoelectric generation, as the temperature gradients would be entirely too small. Given that, you'd have to evolve a thermoelectric large-scale organism from an ancestral biosphere that would have been largely made of _non_thermoelectric organisms. Maybe I'm being overly conservative here, but it seems dubious in the absense of purposeful tinkering. $\endgroup$ – Starfish Prime Apr 24 at 18:54
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    $\begingroup$ @luis.espinal Well what was his description of the alien race? Where they human like or where they made of metal? Imho, the idea is rather contrived. $\endgroup$ – Rob Apr 24 at 20:00
  • $\begingroup$ In Niven's universe, they resembled a cat-o-nine tails, a being with a flattened body filled with superfluid helium, a "head" on one side and multiple "tails" on the other. For charging themselves, they place their "heads" on a light source, and their "tails" on a dark, colder position. The idea is weird, but the novels are very rich IMO. It's the biology angle that interests me (sans I acknowledge it requires significant suspension of disbelief.) I do like @Willk's answer, though. $\endgroup$ – luis.espinal Apr 25 at 13:35

Intelligence comes from competition with conspecifics.

Thermoelectric metabolism is OK. I envision something on a hot stone with cool water washing over it. It harnesses the transfer of heat energy thru its body. I bet there exist microbes like this in the deep earth where such niches are commonplace. They would not be culturable but their existence would have to be deduced by DNA sampling - evern then we would know they were different but might not know how they earned their livings.

Re big creatures: I could imagine a colonial mat which conducted this kind of metabolism, or a giant single cell like an algae with roots on the heat and fronds (here radiators) in the cool.

But smart creatures are hard to imagine for this lifesty;e. These things are basically plants. Once they find a good spot that will be a good spot for a long time. Plants don't need to be intelligent because the adult plants are not going to move.

If your creatures are going to move then intelligence might help. You don't need intelligence to move (amoebas move) but if your perception of time is on the same scale as your predators / competitors, intelligence might help figure out where to go. Maybe these creatures need to move from place to place to capitalize on shortlived sources of heat (or shortlived sources of cold). If they can figure out where to move next that might be a reason for intelligence.

Once you are moving to someplace good, you are trying to get there before your neighbor. I think that you should have intelligence evolve thru conspecific competition. That is why humans are intelligent - because we are descended from humans who outsmarted other humans, got all the good stuff, and had more babies. Your creatures get energy in a lazy way but they need to scrounge up whatever their bodies are made of which is not electricity. They need nutrients. Maybe they go looking for that and for mates. Maybe intelligence is attractive in a sex partner. That search and competition is where intelligence gave the ancestral organisms an advantage.

  • $\begingroup$ Wow, I love this. Thanks! $\endgroup$ – luis.espinal Apr 25 at 13:28

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