What is plausible biology of ocean-dwelling, tool-using, intelligent creatures?
I want to develop a water-dwelling, intelligent species that could ultimately reach space.1 My question here is about the biology of such creatures.
I want my creatures to live in the water, not move onto land, but shorter outings onto land not only would be ok but would help my plot. This makes me think somewhat of whales and dolphins, which breathe air, live in water, and cannot survive long on land (at least without special intervention).
But whales and dolphins don't have anything like hands, and tool use is an important step along the progression that leads to advanced technology. While some dolphins use tools, capacity without something like hands seems limited. (If I am suffering a failure of imagination, feel free to challenge this in an answer!) We know that amphibious creatures can evolve hand-like parts; none of the examples there are very advanced, so I don't know to what extent this "goes with" the other developments I need.
Access to land implies some mobility on land. I assume this means something like legs (with flippers?). My creatures are native to the water, so it makes sense to me that mobility on land would be harder, but it should be possible.
I'm not looking for magical approaches like selkies.
How should I approach the biology of my water-dwellers? What combinations of breathing methods, appendages for tool use, appendages for mobility, and developments that support intelligence are most plausible?
I am aware of this question, which asks how a deep-sea civilization would evolve in a particular environment. I'm willing to adapt my environment to fit my creatures, rather than going the other way around, so while that question is somewhat helpful to me, I don't think it's a duplicate. I'm also aware of questions like this one and this one, which are about technological development but not about biology.
1 For purposes of my story they don't need to develop spaceflight, just use it. The water-dwellers want to leave their planet because the land-dwellers have polluted their environment beyond repair. If they can steal a ship from the land-dwellers and adapt its environment for their needs, that's fine. But they need to be advanced enough to operate it.
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Evolutionary biology: the first effective tool user wins.
In most marine environments two issues dominate most niches: (1) obtaining food and (2) not becoming food. I posit that your creatures will need to become tool users on their way to space. In that case, my intuition is to look at where/how tool using would give them an advantage earlier on.
I posit that the first creature (in your planet's large waters) to use tools effectively for getting food and self defense would out-compete the competition, thus having claws, tentacles or other dexterous appendages is a good starting point. Imagine either crabs or cephalopods wielding sharpened razor clams or augur shells (long, thin cones) as weapons against prey or would-be predators. Sharpening a shell (or bone) on the right kind of exposed rock is plausible underwater.
Side question: Is the chemistry of these waters such that any native (in elemental form) metals might persist long enough underwater to be used? Perhaps as a side effect of a recently dormant underwater volcano? (Or a plant species that conveniently concentrates/precipitates some metal?) Metals are probably essential to any non-handwavium, non-magical spaceflight. Native copper was a big trade item, before the iron age.
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As far as we are currently aware, the most intelligent things in the oceans are the cetaceans (dolphins and whales) and the pinnipeds (seals, walrus, sea lions). Further, it is more tempting to want creatures close to us biologically to behave more like us as well, especially in fiction. Again, the closest cousins to hominids in the oceans are cetaceans and pinnipeds.
However, if you want something alive today to reach the point of being able to drive a space craft, I think you need a cephalopod (octopus, squid, cuttlefish).
As the linked Wikipedia article describes, many cephalopods have demonstrated spatial reasoning, puzzle solving ability, tool use, dexterity, and communication1. The larger ones have brains as big as ours.
Also, as another answer confirms, cetaceans need their flippers and specific body plan for speed and agility while swimming, and to chase down their prey- even those who only eat krill. Evolving any part of themselves for gripping and dexterity would come at extreme cost elsewhere. The same would be true for pinnipeds, who already have hardship enough hauling out on a beach to mate.
Other fiction works have explored a future where cephalopods continue to evolve and advance, such as the speculative squibbon. For the most part, they come to the same conclusion- there is nothing to prevent these creatures from ultimately becoming as capable as humans of manipulating their environment.
To get to the point where one can flood the compartment of a Saturn V and take the controls is not that much of a logical leap. I would expect the first ones to begin the charge would be ones in captivity, where we are already teaching them to open jars, take photographs, and predict soccer matches.
Edit: I almost forgot: http://xkcd.com/520/
1All the more impressive given that their "language" consists of changing their body color!
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Inspired by fuzzys approach I made some thoughts regarding possible underwater skills, tools, etc.:
Tools
- Many already said that remnants of hard shelled exosceleton animals or corals can be used as tools (like knives).
- There are certainly some sea plants to make ropes from. These can be a starting point to make nets or are used as fences against hostile animals.
Skills and Techniques
- Underwater surgery using those non-metal knives could certainly be possible.
- Aquacultures (see below)
- Art (see below)
- breeding animals to fit their use
- brain surgery on aggressive animals if taming doesn't work (to be able to direct them)
Farming Plants
- Growth of Corals can be regulated on purpose for several reasons (like Sponges, Food, Art, Architecture).
- Seaweed or similar plants to make ropes.
Aquacultures and interactions with animals
- Using ropes as fences, or a tamed potentially aggressive animal as herding animal, it can produce aquacultures for food, as a kind of underwater zoo, or other purposes
- aquacultures can be a food basis for bigger tamed working animals
- they can also be used to culturize and tame more powerful animals
shell aquacultures can be used to produce perls and mother-of-perl for art and hard shells as a tool basis
As this species is more intelligent than others underwater it can produce similar effects like between humans/wolves/dogs. So there would be at least one other species which developed side by side as a companion like dogs evolving from wolves as some of them outsourced the hunting to the humans concentrating on their remnants for food. Of course this animal would look quite different than the one it evolved from.
- whales could help moving large objects using a harness of ropes
- tamed sharks or orcas as protection against aggressive animals
Medicine
- Using poisons as a basis for producing medicine
- use of non-metal scalpells and saws
- syringes can be made from a coned shaped shell as needle in combination with an air bladder of fish for the medicine and a second shell around the bladder to reduce or enlarge the size of the bladder therefore injecting or taking fluids
Possible ways of leaving water
- breeding crabs as hosts / living environmental suits for land walks (possibly in combination with surgery)
- Flying could be possible if the atmosphere has a quite high CO2 atmosphere as that gas is quite heavy. So if they can produce gas which is lighter they can use it to fill a balloon made from whaleskin.
- They could also try to breed fish like giant sharks to develop a giant air bladder which can be used as a tool or basic material. Maybe they can even try to alter their physiology over time to produce a different gas which is even lighter than CO2.
Art
- Culturizing corals can be a great way of sculpted living art.
- Pearls and Mother-of-Pearl can be a elements in decoration (like tools, sculptures, architecture)
Higher Industry and other resources
- I am not sure about that, but one approach could be to use heat/hot water of underwater volcans.
- For using them they would also need environmental suits against the high pressure. I am not sure wether they might be developed before or after the environmental suits for land walks or flying?!
- Mining for certain minerals, gems etc. would also be possible under water, but I am not sure which ones could be of use under water. Maybe in combination whith an underwater volcano industry?!
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To have technological civilization, at the very least you need to have tool usage.
Octopuses have been found to use tools with their very dexterous arms.
You also need a large brain and if they are to be able to survive on land for some period of time that seems to suggest a mammal.
So a mammal with large head and a few dexterous arms which can be used for swimming and walking on land as well as tool usage.
Sensory wise, if they are primarily oceanic species, sonar seems plausible.
Obviously, living in liquid they'll be very streamlined.
Finally, they need to have a social structure, work well in groups, which also seems to suggest a mammal.
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