Erm… you’ve just defined bilateral *asymmetry. *
How do you figure?
It’s asymmetric only compared to radial symmetry.
As for something completely different, suppose we had a species capable of organically synthesizing various strong acids and other chemically-interesting substances. Such a creature might evolve the ability to squirt that acid with very precise aim, and so carve useful tools out of blocks of metal or stone: Presto, a tool-maker without hands.
Who is providing the blocks of metal?
“We are actually speaking Rigilian, which by an astonishing coincidence sounds exactly like your English.”
-Kang, The Simpsons
There is such a thing as convergent evolution where genetically unrelated creatures develop similar looking traits. But I think that would be very unlikely with space aliens.
In fact, an alien race might be so different from us that they might not recognize us as “intelligent life”. Just a planet covered in some weird hive of squishy little creatures building lots of various size boxes and emitting weird radio signals.
Alien wombat-analogues. They eat ore and poop metal cubes.
You don’t understand the definition of bilateral symmetry.
Chronos wrote “metal or stone”. Both stone and many metals can occur in natural states, and even if they aren’t presented in a useable form they can be separated by any number of chemical processes without fire (smelting) and forging.
In threads such as this, the discussion seems to inevitably degrade to someone insisting that because humans needed hands to build tools, and because tools are necessary to build more complicated devices, therefore all aliens must have hands, and from there trying to reason why bipedalism, a brain and sense organs at the top of the body, et cetera, until the supposedly logical conclusion is the inevitability of human-like aliens. But the basic assumption that tools like the ones we use, and the technologies we build with them are the only path to industrialization, energy management, and eventual space travel or communications is not in any way validated. Alien life will almost certainly use technologies and methods that don’t even occur to us, and while they have to obey the same physical and chemical laws, they may be evolved in environments that are so different that we would struggle to conceive of their applications while our tools would never suit their uses.
Arguing that only our path to tool use and our resultant technologies are the singular route to intelligence and exploration just illustrates a lack of creativity and independent thought, not the impossibility of alternatives.
Stranger
but they aren’t genetically unrelated. On earth, all animals are genetically related. If you started with something that was really truly not genetically related to earth animals, you would probably end up with something that was rather different.
Maybe… But the more Earth-like the origin, the more likely they are to be solving similar problems with a similar chemical tool set. There are a lot of very basic physics principles at work. We don’t have any genetically unrelated life forms to compare, but we can look at the things people build and find lots of “convergent evolution” going on.
For example, simple physics drives convergent features in both mechanical cameras and human eyes. They are similar at more than a superficial level - lens, iris, retina, nerve, brain. And while Earth has plenty of other eye examples, we think this particular model has arisen more than once.
Likewise, swimming quickly will always favor an elongated body shape because that’s just how liquids work. To draw another mechanical example, there’s “convergent evolution” driving similarities between birds and airplanes and whales and submarines.
How about four legs? It’s a hell of a lot more stable than three, and it’s cheaper than five or more. While Earth has plenty of experiments on number, placement and type of legs, elephants and trucks don’t rely on any common genes to end up looking more than a little bit similar.
There’s another similarity between trucks and elephants: sensors up front, exhaust out the back. This isn’t a guaranteed result either, but it’s not exactly a coincidence. There are good reasons for it. At a biological level, smell-taste-mouth-brain-eyes are closely associated for good reasons, and there are equally good reasons to put excretion somewhere back there.
So, anyway, I’m the biggest critic of Star Trek foreheads there is, but my money says any alien life will have some basic traits and shapes that we will recognize, if not from ourselves, then from other Earth life.
I only nitpicked the metal.
Generally speaking, the metals that occur in natural states aren’t so susceptible to acid corrosion.
Smelting or forging carried out by non-tool-users?
You would end up with something biochemically different, but a great many of the products of evolution are solutions to macroscopic problems of mechanical engineering, optics, or other physical stuff. It’s of course not guaranteed that every form of life will ‘try’ to come up with physical solutions to macroscopic physical challenges - they might circumvent that altogether - but it’s a fair bet that many will.
He said without smelting or forging. Chemical separation processes.
There are iron-reducing bacteria on Earth that can produce iron-rich structures. Geobacter metallireducens is known to produce magnetite crystals, for example. If our hypothetical sapients happen to use internally generated electromagnetic fields to move and/or manipulate their environment, building stuff out of magnetite would be handy. Microorganisms that produce other metallic compounds are certainly plausible as well.
Or, you know, wombatoids.
assimilation-they are already here.
Even if an alien race looked very, very similar to us, there’s no way they’d have gingers. That would be just too weird.
ah. My mistake. Sorry.
He’s defined front and back being different, but absolutely nothing he says refers to biradial or bilateral symmetry.
Okay, so these hands-free aliens can create tools by precision squirting of acids on boulders they find laying around.
Now, how do these hands-free aliens go about using those tools?
Internally generated electromagnetic fields to manipulate ferrous tools. Finely controlled jets of liquid. Adhesive body surfaces. Biochemical control of symbiotic colonies of sessile lifeforms that attach themselves to the tools.