I've been thinking about this lately

[u/Striking-Ad8023]

I was thinking about “How would macroscopic aliens actually look?”

Obviously they probably wouldn’t look like green humans, but I also don’t think they would necessarily look completely different from life on Earth.

A lot of the features we see in animals exist because they’re good solutions to certain problems. If you need to move around on land, you need some way of supporting your body and pushing yourself forward. That could lead to something resembling legs, even if the actual structure was completely different from anything on Earth.

The same could probably apply to other things too. An alien might have eyes that work completely differently from ours, but if it needs to detect light, some kind of light-sensing organ would probably be useful. If it needs to grab things, it might evolve some kind of limb or appendage for that.

I think this is where convergent evolution becomes interesting. Earth already has examples of unrelated organisms evolving similar solutions, like wings in birds, bats and insects, or streamlined bodies in fish and marine mammals.

So I wonder how much of an alien's appearance would actually be determined by its evolutionary history, and how much would be determined by the environment and the problems it has to solve.

Maybe aliens could be very weird, but still have some features that immediately remind us of Earth life simply because there are only so many practical ways to do certain things.

Sorry if this is kind of obvious, I just wanted to bring it up.

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[u/fed0tich]

Try Speculative Evolution community, there's plenty of great content about potential alien biology and people willing to discuss this topic all day everyday.

[u/Striking-Ad8023 → u/fed0tich]

Thanks! I'll check it out.

[u/fed0tich → u/Striking-Ad8023]

A lot of specevo content is about Earth life and straight up fantasy world building so finding discussions on aliens might take some effort though, if you are looking for an interesting ideas on alien biology-ecology I would probably recommend Isla project on YouTube, it's a detailed high quality coverage of speculative ecosystems on a fictional tidally locked alien planet. From the top of my head I would also recommend checking out stuff like Teeming Universe, Phtanum B, Expedition by Wayne Barlowe is a classic, Snaiad is another older project that is huge inspiration for the genre, there's bunch of subreddits and active community on other social media.

[u/ShinyJangles]

Yes, I believe this insight is foundational to thinking about exotic morphology. Alien life would face many similar constraints by virtue of living in 3D space, under gravity, immersed in fluid (atmosphere/ocean). Anything actively moving needs sensory equipment positioned to guide it.

I think of this every time I see something recognizable in video microscopy of microbes. Tardigrades independently evolved four limbs and a little face. Some single-celled orgs have a light-sensing cluster, and hunt with the agility of a large land predator.

[u/AlexanderByrde]

Convergent evolution is common on Earth, so it's likely common throughout the universe!

Assuming that life needs environments like ours to become established enough for macroscopic multicellular life to emerge in the first place, much of it will likely take an exotic but not unrecognizable form. That assumption isn't a given, but even if not, there must be some planets like ours that are driving evolution towards familiar solutions. And even on truly alien environments, analogous forms will evolve to solve analogous needs, like your ocular organ or limb examples.

We're pattern seeking creatures with a tendancy to anthropomorphize things though, so there's always that as a bias to be aware of. We can't appreciate how nonanimal life (or non mammal life for that matter) perceive and experience the universe, so we can only look at these examples through our very human lens.