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In some science fiction and fantasy settings (mostly fantasy) there are sometimes things like rock giants or rock golems. Basically, what I'm getting at is rocks forms with, sentience in some cases. So I was wondering if it is at all feasible for beings like this to evolve into human like creatures. They do not need to be made entirely of rock, I suppose, but how far from rock would they have to be? How would their bodies be able to function if it was possible?

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  • $\begingroup$ I think scales are probably as close as you would get. $\endgroup$ – FiringSquadWitness Oct 7 '15 at 5:58
  • $\begingroup$ . . . or shells/bones, which are essentially a type of rock. $\endgroup$ – Neil Slater Oct 7 '15 at 6:14
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    $\begingroup$ like... erm... coral? $\endgroup$ – user6760 Oct 7 '15 at 6:46
  • $\begingroup$ Bear in mind these are usually animated using some external forces, not biology, so it doesn't really make sense to think of biological evolution. Think more along the lines of a robot made of rock instead of steel. $\endgroup$ – MichaelS Oct 7 '15 at 6:56
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    $\begingroup$ relevant: How could something like a Gargoyle evolve? $\endgroup$ – sumelic Oct 7 '15 at 7:12
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Go for a silicon based life-form as most rocks have a high quantity of silicon in them. While not strictly a Rock-Being as we are accustomed to thinking about them in fantasy stories, a silicon based organism would share many characteristics with the Rock giants you want.

They will need to eat stone or stone like substances for food. As long as the evolutionary process is right, there's no reason they couldn't be as intelligent as humans.

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  • $\begingroup$ After they evolved into what you are describing could the walk around and live on a carbon supporting planet like earth? Could they survive outside of their planet? What would they need other than rocks to sustain themselves condition wise? $\endgroup$ – Sunspear25 Oct 7 '15 at 14:05
  • $\begingroup$ Your last question I can't answer because silicon biology falls into theoretical xenobiology. Conceivably they could survive outside their own planet and they may function in a carbon-based biome but may require some support mechanisms to make that happen. $\endgroup$ – Green Oct 7 '15 at 14:12
  • $\begingroup$ I guess you cannot have silicon based life forms evolve at all. Our home planet has huge reserves of silicon, yet not a single multicellular complex organism that can digest rock or sand. The main problem here is that silicon based compounds are water insoluble and for digestion, water solubility is a must-have. No life form that we know of, can assimilate solid state particles directly into their metabolism. $\endgroup$ – Youstay Igo Oct 7 '15 at 14:41
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    $\begingroup$ Life doesn't have to use water as a solvent as there are other options. The trick with silicon-based life will be get it in an environment where carbon-based life can't exist or has a severe disadvantage compared to silicon-based life. Higher temperatures above 41C make carbon-based proteins break down. On a hotter planet, these kinds of conditions wouldn't be hard to come by. $\endgroup$ – Green Oct 7 '15 at 14:44
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    $\begingroup$ Ok that makes sense. What would work as a solvent for them? I'm not sure if water would be a good idea (maybe it is I'm at a loss when it comes to biology of silicon life forms haha.) What would they most likely breathe as a silicon life form anyways or would they most likely deal with similar elements? Sorry for all the questions I'm just getting prompt responses from you. $\endgroup$ – Sunspear25 Oct 7 '15 at 15:06
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If you have a body made completely of rock, the best you can get is a statue. As far as I know, they are dead pieces of rock.

If you have a body with its skin made of rock, you are asking for the same thing. Rocks have zero elasticity as far as I know. So if/when your character moves a muscle, its body will crack at some point and it will bleed to death.

If you have a body made of skin like normal creatures but bones made of rock, this is not possible biologically. Rock is all silicon. Earthly organisms (all of those we know about) do not digest silicon or have systems for converting silicon compounds into rock. The closest there is, are calcium and phosphorous metabolisms, converting them into bone and shells (of sea creatures). Rock tends to be extremely weak when as thin as a bone. Also it is very much heavy and frankly it will hurt your hip muscles like hell when you sit down. Ouch!

So no, practically speaking, you cannot have any creature made of considerable quantities of rock inside its body or outside.

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    $\begingroup$ Barnacles and corals have squishy insides and a rock-like shell, as you yourself mention. So it is possible to have a creature with rock as its outer shell. But of course the shell/carapace is almost completely rigid, although according to this link: whoi.edu/science/B/people/kamaral/Barnacles.html , barnacle shells have openable "doors" with biological hinges. $\endgroup$ – Lostinfrance Oct 7 '15 at 7:42
  • $\begingroup$ In general, you are right. But specifically related to this question, your examples are out-of-place. In some scifi and fantasy settings (mostly fantasy) there are sometimes things like rock giants or rock golems. OP wants more mobile, intelligent and active life forms. Otherwise, he could even have gone for a en.wikipedia.org/wiki/Glyptodon which I reckon was the smartest of all shelled organisms. $\endgroup$ – Youstay Igo Oct 7 '15 at 8:08
  • $\begingroup$ Rock on the outside could work if it is segmented like armour. You would probably need a more normal skin for the "water proof layer" with the rock plates on top as armour $\endgroup$ – Richard Tingle Nov 23 '15 at 21:35
  • $\begingroup$ That is one side of the matter, as in, if a creature could survive with a rock armor. It is another thing to build rock (silicon) based armor from within the body. We are talking about a sand-eating creature here. Very very complex and unlikely, I would say. $\endgroup$ – Youstay Igo Nov 24 '15 at 5:14
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perhaps something like an assassin bug or decorator crab: instead of being literally made of rock, it sticks rocks to its outer hide as an easy means of self-defense. this would be pretty easy to evolve, as you basically just need sticky skin. this would let you have golems of multiple different shapes, sizes, and appearances. another fun idea: as the organism grows older, it could accumulate more and more layers of rock, eventually becoming so heavy than it transforms into a sessile adult form, more like a barnacle, and possibly changing into a female as well. at this point, its main source of nutrients would be any animals that wander close to whatever "mouth" it has, and it could reproduce by attracting one or more male mates and than raising the young inside itself. the crab comparison actually makes me thing of a rl example of what im thinking of: there is a species of crustacean that begins life as a standard, shrimp-like larva but on reaching adulthood enters the body of a fish and morphs into a network of parasitic fibers. the rock monster could work similarly: the young are hard-shelled insectoid creatures with stone shells, the second stage of life sees them start growing connective fibers and adding more and more rocks to their body, and finally turning into a large pile of rock-covered flesh with the original body in the center.

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Maybe you could want a silicon-based being.It wouldn't be very Earth-like (silicon cannot do all the things carbon does)and it would be very different, but, if we suppose intelligence evolves when it's needed to resolve adaptation problems, I think it could be sentience. Silicon can work where a planet is too hot to allow carbon to work (look at this). I hope it helps.

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No. A self-repairing self-building object will need an internal distribution network and units that are chock full of machinery for building and maintaining the unit, with structural support being a trade-off with all the stuff needed to make it work. Most of the stuff will be nanomachines intended to fill a role, not just be a rock.

In short, cells are full of stuff needed to make it live.

Bones are crawling with cells to dissolve and lay down mineral, and is a composite with protein as well as mineral, and shot through with blood. Shells and tests can be secreeted with various mechanisms, but require living tissue to generate it.

An armored creature or big shell is not what you mean, right? You are asking of rock = living tissue. It's not.

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  • $\begingroup$ The thing is it wouldn't be self repairing actually. One of the traits of the creature is that if it's injured it would be permanent. The reproductive cycle would be the hard part I suppose because then it wouldn't really be able to grow. I don't know I was just tossing the idea around. Also no, a shell isn't quite what I was looking for. $\endgroup$ – Sunspear25 Oct 7 '15 at 14:10
  • $\begingroup$ Then in what sense is it alive? Is it made of large-scale machine parts like a pnumatic bulldozer? Tyen how did it "grow"? $\endgroup$ – JDługosz Oct 8 '15 at 1:19
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Since you're just "tossing the idea around", what about a being with a special affinity with rock? It's born as a biological being, possibly slug-like but long and maybe with tentacles, and capable of secreting rock-disolving acid (or has some other rock-shaping tools).

As it "grows" it's actually collecting the surrounding rocks and fusing them with itself shaping it to "build" its body, until it has collected enough rocks to form the armour or bones or whatever else you need to consider it a rock-person, while original organic bits form the muscles. At this point it's considered to be at full maturity.

The creatures could only be reared in rocky areas, of course.

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You could take some inspiration from Diatoms, they're coral-like free-floating algae that use Silica instead of Calcite to build an exoskeletal structure. Basically you'd have an inert "rocky" silicate layer wrapped around a life-form that is carbon-based and can be pretty much human in terms of biochemistry and anatomical structure. With the right structural considerations, under limb freedom and skeletal anchoring, you could easily have ten or twenty centimetres or even more of rocky material over your otherwise human analogous creature.

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