What sort of evolutionary possibilities are plausible for a human-like species orbiting a red dwarf star?

Question

I'm working on a story which is sci-fi so soft you could spread it on a cracker, but I'd like something semi plausible. I'm very likely overthinking things to an extreme, but I'd like someone with more of a science mind than I, to tell me if what I have is plausible on a surface level, or if there are certain blindingly obvious things I'm not taking into consideration that would trash this entirely.

I've included as much relevant information as possible, but to try and keep the question as narrow as possible, I'd like to focus on adaptations for the light emitted by the star and the wavelengths they're capable of seeing and how that might affect their appearance.

I've already looked at this question, which is similar in scope (human-like origins and general Earth-like plausibility), but that's taking a pigment and working backwards, whereas I'm looking for what might naturally arise given the conditions available.

The Setting

The basis of it is a tidally-locked, Earth-like planet around a red dwarf star, and for all intents and purposes, assume it's habitable to humans atmospherically and pressure-wise. Assume through heavy doses of handwavium they are able to control for factors like solar flares that might be a civilization-destroying problem. The light the planet receives is clearly dimmer and in a different wavelength than our sun. It obviously receives heavy doses of infrared and red light.

It is an "eyeball planet", but a decently thick atmosphere (that may be artificially supported) and oceans manage to ease some of the more extreme temperature changes. Assume that, as with any eyeball planet, there are strong winds from night to day side. (This may cause a gradual pressure to live partly or completely underground, both as a radiation shield and protection from winds.) I'm thinking if there are plants (or anything that uses photosynthesis), they're likely black or very dark.

The Species

One of the intelligent species of this planet are "humans" (pseudo-humans) initially created by another intelligent species (who has colonized the planet and evolved to adapt to it, but not originally from there). Think "Avatar, but the aliens create pseudo-humans to interact with other humanoid species because their weird alien bodies don't communicate very good" and you've got the gist of it.

Think of the aliens as...intelligent like mycelium is intelligent: something with a sort of collective mind and senses. In their long ago past, they had a focus on communicating through light and shifting colour, remnants of which are still around, but they're less mobile now in favour of rooting to the earth. They are one aspect of an overarching collective mind that uses created bodies to communicate with other species.

(See above about heavy doses of handwavium. I bring this up only because the focus on light and colour has some relevance.)

Pseudo-humans start off artificially created, and then eventually reproduce on their own and become a self-sustaining population the aliens can 'pick' from. The aliens and pseudo-humans have a symbiotic relationship that ensures there's no competition for the same resources and enough benefits that they'd be cool with them occasionally controlling your body like a meat puppet for a bit. It's a weird trip for sure, but usually they come out of it no worse for wear.

They are visually identical, but a recurring theme is that they are not human and such are capable of things that humans aren't (they can see into wavelengths that humans can't, I'm thinking UV but IR might be more plausible). Why? Well, the aliens might've slipped a little bit of their own genetics into it because it was available and easier, shhh. They have a range of skin/hair/eye tones as we do, although the underlying pigment doesn't have to be melanin, just so long as it looks like it to a human (that is, shades of brown/red in varying proportions). The aliens and pseudo-humans cull any mutations that are too wild (they want their human-sonas to be accurate after all).

Like humans, pseudo-humans adapt to their environment and adapt their environment - dwellings can, at various points, be a mixture of above-ground dwellings, possibly shielded with regolith or dirt, or possibly even mycelium-like tendrils from the aliens, or below-ground dwellings to shield from excessive radiation.

The Premise

The alien civilization collapses entirely, leaving the pseudo-humans to evolve and adapt on their own. The loss of their symbiotic relationship would be a huge societal blow, but assume the pseudo-humans manage to make it through the dark age/population collapse and don't go extinct. The story is set about a million years after this collapse, as I believe that might be enough time to see significant changes.

I'm focused on the light emitted by the star and their ability to see into different wavelengths and adaptations for simplicity's sake. I'm doubtful there would be significant (visible) anatomical changes after a certain point, and I want there to be some sort of visual continuity (that is, you can see the human influence in them, this is not a Man After Man or All Tomorrows situation.)

The Question

Given the elements outlined above, how would a species that is visually similar to modern humans, but have increased visual capabilities, adapt to the dimmer stellar light and differing wavelengths of light emitted by a red dwarf star over a million years? I'm thinking of:

• A change in the eye shape or size to handle the different wavelengths of light they can see compared to a human (proportionally bigger in the skull/more visual processing sections in the brain, or different colours or pupil shapes)
• Would the pigments in the skin/hair/eyes adapt to better protect against IR and/or red light, which a red dwarf will put out more than UV? If so, which colours would be most likely given the current constraints of human-like pigmentation? Or would there be no change overall? (I'm interested in both changes visible to pseudo-humans and changes visible to the normal human spectrum, or if a normal human can't see anything different but a pseudo-human could)
• Or, would there be a skin tone that is more likely to crop up over time? Would the dimmer light of a red dwarf create evolutionary pressure for lighter skin, particularly if there was a push to remain underground?
• Given that a red dwarf emits red light, would there be a significant visual change in colours overall? (I read somewhere that under a red sun, blue eyes wouldn't look blue, but I can't figure out what colour they would look like).

I fully admit this question is broad, so I appreciate if it gets closed for that. I'm just wracking my brain here trying to figure out if any of this does play a role, and what that role looks like, or if "they look like humans even a million years later" is good enough.

Answer 1

all of the above. Also? they evolve into ants. If these beings are not already adapted to a red dwarf’s intense radiation, then they had bloody well better adapt toot sweet. Red dwarfs are nasty as stars go, and any life that evolves on planet’s orbiting them had better be well-adapted or they will go extinct.

Radiation tolerant skin? That’s a must. UV or IR vision? Yes please! Big eyes? Well, a red dwarf emits less than a thousandth of the sun’s intense light, so yes, you want eyes that would slay the whole of Hollywood.

Why evolve into ants? You describe these pseudo-humans already having a hive-mind and living in semi-underground dwellings; societal collapse means loss of agriculture and safety, and so they retreat even further below ground and allow only one female to breed at a time to minimise their food needs. As time goes on, this becomes the norm for the species, and once they are fully adapted for life on this world, they can find food more easily, but rather than return to everyone having babies, the matriarch just evolves to produce more. Immature females and males become workers, with most remaining immature until the queen dies, whereupon they all become sexually mature and leave to mingle with other colonies and start new ones. I give you homo termes; the termite man.

Answer 2

1. They (mostly) dwell on the dark side. The hard radiation on the light side is bad for life. It is good for adding energy to organic molecules, though. These blow over to the dark side and are the base of the food pyramid, feeding fungus type organisms. It is not pitch black over there - the solar wind produces constant bright auroras which light the sky.

You could give your people larger pupils like nocturnal animals have. You could give them epicanthic folds to do whatever those do. You could give your people nicitating membranes for wind protection.

2. They are many. In the days of the mycelium civilization there was not a need for a lot of humanoids. Their populations were controlled and kept at a low level. Now that has stopped. The population of humanoids has expanded to the carrying capacity of their world.

3. Genetic drift.

https://www.roadsideamerica.com/story/29130

/The aliens and pseudo-humans cull any mutations that are too wild (they want their human-sonas to be accurate after all)./

In these post-mycelium days, there are no longer culls. The mycelia had standards but the humans are not so particular about how they appear. On this alien world there is really not much selective pressure on these humanoids. With the expansion of their population there has been genetic drift. Just as absent selective pressures against them, local urban populations of black or white squirrels occur in the sea of gray squirrels, your population of humanoids have local populations who differ considerably from the larger whole.

There are selective pressures elsewhere that have altered populations. This includes the brightside dwellers, who have become quite different. The aquatic people are more different yet and might almost be a different species. These groups can appear in seasons 2 and 3.

4. Ability to meat puppet has become a rare trait. There was selective pressure in this direction. In the waning days of the mycelium civilization, there were some persons who could not be possessed by their alien masters and compelled to cull their babies. The trait thus conferred better genetic fitness. In these latter days there are still some people who can host mycelial minds but the relict mycelia are less interested in doing that. Most of them are less interested. The god of the Brightsiders is an iconoclast and remains very involved.

Answer 3

Too many possibilities

I'm not a biologist, but I have toyed a lot with artificial life and such, and there are some essentials that probably apply universally.

Evolution as a process is only limited by factors such as time, "luck", resources and the genetic code. In the end, it does not matter what kind of environment it is happening in, as long as there is a chance that anything benevolent can happen and repeat itself. Red dwarf as a sun should not be anything exceptional.

Red dwarf may offer more time, though, but it also offers less high-energy radiation that provides a higher chance of random changes happening that are one half of what evolution is driven by. The other is selection, so evolution might on average be running slower but it has a chance to run longer when compared to Earth. Maybe it affects diversity, different species being more alike, or maybe not... there is no guarantee at all.

Genetic code can be brittle, which means that small changes impact survivability so much that most mutations cause problems, in which case they rarely accumulate into bigger changes. Or, it can be robust so that organisms can accumulate smaller changes into bigger ones that eventually add up to a completely new functionality.

But, this has hardly anything to do with environment apart from the fact that in environments where random mutations occur more frequently, genetic code might protect itself better, resulting in stubbornness against evolution (see eg Deinococcus radiodurans). So, maybe genetic code on a planet orbiting a red dwarf is less protected, but there are so many other factors that sun alone is not enough to tell whether this is the case.

So, in the end, maybe luck matters so much that anything goes.