The word is Carcinisation

reminder:

You guys should read the Stormlight archives. Fuckin everything is a crab, even the plants.

If this post is awakening some weird feelings in you, there’s an episode of Futurama you might want to watch.

But what if the human form is a prerequisite for evolving into the space age? We wouldn't need so many tools if we were strong as a crab to begin with

A fairly small number of known species evolved to the vaguely humanoid form, but 100% of known species with a human level of higher intelligence have had roughly this body plan, it's really not unreasonable to extrapolate that this could be a common body plan for intelligent aliens.

Life can have infinite forms and can exist and evolve in the most inhospit environments. But an advanced tecnologig species only can exist in certain environments and with reduced posibility in their appearence. Aquatic beeings can be intelligent, but never can create advanced tecnologies. The basic condicion of advanced tecnology is the domination of fire and electricity, not possible in the water, it need Oxign in the atmosphere.

They must have limbs skilled enough to handle and construct this technology, a complex communication system, and a binocular vision system (for this reason the most used in all species) to perceive their environment. The humanoid shape is one that best fits these maxims and therefore it is quite possible that an advanced species would also have a more or less similar shape.

It is known as convergent evolution, when unrelated species have a very similar physique to each other by living with the same challenges in similar environments. Evolution always use similar solutions for similar tasks. A good example is the genet, which looks and behaves very similar to cats, even with retractil claws), but they are a completely different species (Viverridae)

Project Hail Mary got this really right. The aliens are big rock crabs

You know who's not a coward? Captain James T Kirk.

Funny to think about it: Crabs are a huge local maximum of peak evolution

Someone needs to rule 34 crabs. And then delete their Internet history as thoroughly as possible.

I doubt crabs could make it as an intelligent interplanetary species. I mean claws are cool and all, but really tough to use tools with.

Neal Asher's Praedor Moon is a fun read if you want to see what advanced humans would do against space faring crabs.

The squid bois from Arrival are cool

What is this "crabbification" evolution trend you speak of?

Intelligence favours dexterity of making/holding weapons and tools. Claws are not as good. Armour is always a nice to have, but the offense from weapons use from "hands" is better. I do like the idea of 360 rotating "eye arms" to catch backstabbers. Maybe more arms and legs.