What are we referring to as humanoids though? And what are we about as intelligent? Crows? Crows aren't going to build spaceships and don't really have the means to because a beak isn't a great manipulator, even though they use tools. I don't think the person above is saying that quadrupeds would be out of the realm of possibility (maybe they are. IDK I'm a computer scientist, not a biologist. I could totally see body size, caloric intake ratios, and brain mass being related in a way that would make these unlikely), but rather things like fractaling appendages would be expected because intelligent life would need to have fine motor control. (Is a centaur humanoid?) There are just more efficient ways to do things than other ways. Yeah, maybe alien life will have a beak. Maybe their pupils will look different but I'd still expect them to have eyes with squishy lenses because that's pretty much required to be able to focus and intelligent creatures need to be able to sense things both near and far (without technological enhancements). Light sensing isn't enough if you want to build things, you need depth perception. I think if you follow this line of reasoning you'll find that a lot of attributes humans have would be pretty likely for intelligent alien life as well.
Yes but it is very expensive. Here's some more on bats[0] (mentions expensive echolocation around 5:45 and moving from sonic location to echolocation evolution). Eyes do also convey more information. You can get colors in addition to depth and shape and that's a good reason and easy path for eyes to develop since light sensing is a pretty easy thing to develop. Also, bats aren't blind, despite common belief.
Also consider an octopi's environment. That environment is not well suited for being able to build lots of things. How do you get to the bronze age underwater? How about even earlier. Land based creatures have pretty similar forms. Snake like, bipedal, quadru/multiped, and flying/winged creatures. Snakes don't have arms and so aren't going to have fine motor control. Winged creatures are going to have a hard time dealing with heavy objects (they have hollow bones to fly and wings are incredibly fragile and I don't see nature creating super materials, plastics, or metal structural systems for animals). Quadrupeds probably aren't going to develop arms like centaurs (more likely legs become arms). So if we want a creature that can have fine motor control, live in an environment that can easily create metals, not be extremely fragile, and is able to devote a significant amount of its energy intake to its brain, you're probably going to come up with something ape like (bipedal). There are other forms here, but we can see that there are some pretty good hints that we learn just from mechanics and aren't so much dependent on specifics of Earth or humans.
"Also consider a human's environment. That environment is not well suited for being able to build lots of things. How do you get to the <untranslatable> age on earth?"
Earlier, you mentioned that beaks can't make spaceships. Well, maybe neither can hands. What we call a spaceship might be laughable nonviable. In fact, we know it is.
We're struggling at limits that some other lifeform might not have. We're hill climbing for tools that will let us do things we really want to do. Quite likely a lot of our progress is orthogonal or even oppositional to what we need to do to get off the planet.
We have no idea if some of our progress might be backsliding or entirely halting our future progress. Due to our natures. Due to our beaks.
> Earlier, you mentioned that beaks can't make spaceships. Well, maybe neither can hands.
Except hands did create spaceships...
The "beaks can't make spaceships" is a comment about crows not having hands. Crows use their beaks to manipulate objects. This does not imbue cows with great motor control. The use of tools is very different than the ability to finely manipulate tools. Aliens could have beaks, but these would not be their way to build spaceships. Similarly they wouldn't have pincers. Such grasping mechanisms just are extremely inefficient and don't allow for certain tasks.This excludes a lot of classes of tools from crows. This isn't biology, this is physics.
Our hands are like beaks to some hypothetical species, and it is hubris to assume we're great manipulators. Our fingers could be closer in utility to cow's hooves, than the manipulation techniques of some unknown species are to our own gesticulations.
And they would have tools as multipliers for their natures, just as we use tools to extend ours.
Our wonderful inventions might be another species child's play. Our herculean efforts to reach the stars might be a triviality to a species that can synthesize novel compounds in their bodies, and/or those of their stock animals. We're just at the early stages of doing that with algae, after a very long climb from first making fire.
Just as I could train and arrange to walk to Mexico, they might be able to self modify and reach the stars. No spaceship needed.
Our great ideas and dreams might be trite to bigger minds out in the galaxies. They could have easily skipped over what we struggle with.
You call those cans "spaceships"? They can barely get to your moon and back.
"Humans can't even excrete flexible ceramics. They need air. They need heat. They can't stand up to ionizing radiation. This isn't biology, this is physics!"
Cephalopods have got onto land at least twice. Nothing says they can't do it again.
But this form is also extremely rare. You're also ignoring the main component of the argument, which is where calories are going, not that arms can come out of a body.
Something resembling this has actually been observed in a species of deep sea snails. Iron sulfide is incorporated into the hard bits (shell, foot armor). (https://en.wikipedia.org/wiki/Scaly-foot_gastropod)
That's a wrong way to think about it, since all modern "humanoids" are descended from the same ancestor not that long ago.
And if you consider dinosaurs humanoid, then so is that meme cat that can walk on its two back legs.
If there was an apex predator in every tree of life, in the "humanoid" shape, and I'm talking "humanoid ants" here, then it would be reasonable to assume that there's something beneficial in the "humanoid" shape that helps long-term survival.
And that's not even taking the majority of lifeforms into account - those in the seas, and greatly discounts birds. We still can't agree on if dolphins and crows are intelligent.
So, no, chances that the "humanoid" shape is somehow special out there are basically 0, since it's not even special here on Earth. We're an accident. Insects, mushrooms, plants - all those life forms are better adapted for mere survival than us (judging by cumulative mass of live organisms).
That's the wrong way to think about it. Nothing is 'better adapted' than anything else. Each is adapted to its own niche. And no accidents really - convergent evolution shows that similar ecological pressures very very often result in similar forms. Witness fish ("there's no such thing as a fish") or trees ("there's no such thing as a tree").
And that dinosaur comment - I don't know what to do with that. Dinosaurs only walked on two legs in internet memes? That's so far wrong I can't comment.
Many convergent evolution paths led to the same similar form, in time. That was the point. If the environmental pressures are similar, the forms may be similar.