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Is it feasible that such a race can exist within the following constraints?

Body:

  • Humanoid design

  • Average heights at maturity between 2 metres (females) and 2,5 metres (males)

  • Live birth. One offspring per pregnancy as a maximum (uncertain if design would allow for multiple offspring per pregnancy)

Energy output:

  • No body hair, to drive down the protein requirements in the diet

  • External body temperature below 15 degrees centigrade (i.e. little/no body heat escapes due to [reasons leading to endothermic chemical reactions within body])

  • Females consume as much as males in to sustain them during pregnancy (stored in hip/thighs, mammary glands)

Digestive tract:

  • Adapted to and streamlined for dealing with the current diet. (obviously)
  • No large intestines, based on lack of solids consumed (all waste materials are discharged via one channel [a la urinary tract]).

Energy input and storage:

  • Diet: large bovine milk (cow's milk, or similar), ales, strained soups.
  • Efficient biology allowing for process: sugar -> fat (storage) -> amino acids -> complex proteins as needed.

Autoimmune system and disease prevention:

  • Subpar autoimmune system -- meaning leading cause of death is infection ('energy saving reasons').

There is magic in this world, which leads to the creation of said race (evolution being waved in this case).

Bonus points for any added information based on current data that would describe:

  • what the (in group) social hierarchy would be like

  • how often they would have to drink/urinate

  • instincts born from a group of this race that is enslave and/or has it constantly reinforced that the 'creator' is owed their lives/loyalty

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    $\begingroup$ Not a complete answer, but a liquid only diet exists for humans: soylent.com When it was launched in beta the creator said he had been using it for some time, and I think he advised having 1 day (or 1 meal? I forget) a month that was solid, but otherwise it was enough. So I guess it depends on how flexible your 'soup' is. $\endgroup$
    – Ranger
    Commented Aug 25, 2016 at 17:08
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    $\begingroup$ The large intestines absorb water. You need that. Small intestines mostly absorb nutrients not mostly water. Even a purely liquid diet would still generate stool because 25%-50% of stool is dead gut flora. Breast feeding babies (all-liquid!) still produce solid (mushy) stool. Gut flora is necessary for bio-availability of many vitamins. I say, keep the large intestines. (You can hand-wave the poo though.) $\endgroup$
    – Xplodotron
    Commented Aug 25, 2016 at 17:53
  • $\begingroup$ @Xplodotron Something I should have remembered (pre-caffeination) from my schooling TT_TT $\endgroup$
    – Fayth85
    Commented Aug 25, 2016 at 17:59
  • $\begingroup$ Technically there's no reason why a diet needs to be solid, its just more likely to be healthy. $\endgroup$
    – Mark Rogers
    Commented Aug 25, 2016 at 21:49
  • $\begingroup$ Much of the work you do when eating is about turning your food into liquid. $\endgroup$
    – candied_orange
    Commented Aug 25, 2016 at 22:26

6 Answers 6

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A fatty milk contains 64 calories per 100ml and every nutrient necessary for the baby, including supplements for the immune system. Even your case can evolve naturally. Your organisms can be codependent to say, cows. Your aliens would be more adapted to drink cow's milk and can benefit much better from it. In turn they will protect the cows from predators. Now, if your people need 1280 calories a day due to their efficient metabolism, they only need to drink 2 liters of milk per day. You can even make 3 to 4 liters so that they will have enough calories to be almost as strong as humans.

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    $\begingroup$ Adults need more than just calories. Where's the dietary fibre? Where are the carbohydrates? Sodium? Vitamin C? Iron? Unless this is magic milk specifically meant to solve all dietary needs (more than just bulk calories), it's not feasible. $\endgroup$
    – rek
    Commented Aug 25, 2016 at 20:56
  • $\begingroup$ @rek Actually, I'm not worried about vitamins and nutrients and the like. I can figure out how they have a balanced diet. I am more worried about me overlooking something on a biological level. $\endgroup$
    – Fayth85
    Commented Aug 25, 2016 at 21:20
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    $\begingroup$ @rek no need for magic. Co evolution or genetic engineering and cow or pig milk could be perfect for humans, for example. Except for fiber, but that's only needed to push solid mass thorough digestive system easier. But here, there is no solid to push. Also, some cocktails for sick contain fiber, in suspension. Definitely can happen. $\endgroup$
    – Mołot
    Commented Aug 26, 2016 at 6:05
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    $\begingroup$ Human milk contains prebiotics (which are basically fibers) so for healthy coevolution, our space cows could develop prebiotics for our aliens. Milk contains vitamins and all necessary nutrients. Remember human milk contains everything for a human baby to survive and grow. $\endgroup$
    – Cem Kalyoncu
    Commented Aug 26, 2016 at 6:19
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    $\begingroup$ It could, if it means cows would be safer when they produce a milk with those. If you don't believe in co-evolution look at mitochondria, it is a (most probably) different organism living in our cells: en.wikipedia.org/wiki/Symbiogenesis $\endgroup$
    – Cem Kalyoncu
    Commented Aug 26, 2016 at 19:59
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Well, a "liquid" can contain just about anything. Either something is dissolved (at the molecular level) in the liquid directly, or you use emulsifiers and stabilizers to "dissolve" microscopic droplets (which is how milk has so much fat "mixed" into water), or you have a suspension, like coffee is a suspension.

So, yes. It can be done. Your humanoid species may not need as much food per day as humans what with their incredible heat-retaining physiology. So you can magic up some super smoothie, or you can have people walk around with Camelbaks. Up to you.

Usually the milk of a species is for the offspring of that species. But if your humanoids are jonesing for moo juice then perhaps they have selectively bred these cows to produce milk suited for them, plus they supplement/compliment their nutrition with the strained soups. And ales are always good.

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    $\begingroup$ Actually it is done. Smoothies for sick or pathologically underweight people are made just this way. Except it's engineered up, not magicked ;) $\endgroup$
    – Mołot
    Commented Aug 25, 2016 at 18:34
  • $\begingroup$ but those smoothies would require people to poop them ....cause you know it's not really a liquid but blended solids mixed with water. $\endgroup$
    – Charon
    Commented Aug 25, 2016 at 18:36
  • $\begingroup$ "People don't need that much food per day" because the solid food we eat has way more nutrients than the equivalent liquid weight (even compared to the average off-the-shelf liquid meal supplement). $\endgroup$
    – rek
    Commented Aug 25, 2016 at 18:42
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    $\begingroup$ Yeah, the no pooping thing would require a bit of explanation. But these are humanoids, not humans. Remember these guys also have minimal escaping body heat. So, clearly we are not dealing with regular human metabolic and physiological processes, so who's to say how much food these guys really need? Solid waste is not just unprocessed food. I mentioned gut flora. But also, in humans the breakdown of old red blood cells leads to biliruben which is excreted almost entirely through pooping. We are simply cleaning out dead blood cells. $\endgroup$
    – Xplodotron
    Commented Aug 25, 2016 at 20:03
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They are humanoids so I would say yes, cause humans are one of those creatures that can survive on almost every kind of diet...

in The world there are human diets that include dirt or rocks, diets that include only liquids as you suggested or diets that include only blended food.

And all those diets are ok from a survival view.

What could make more sense for this race is vomiting a really powerful acid that can melt food and turn it into liquid, many animals already do it and it works.

But since your world includes magic spitting acid isn't really needed...

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Yes, people can.

If you want lower tech it may get tricky, since a lot of evolution to get to macro organisms has related to keeping valuable juicy insides inside. Work is needed to be done to get get that food value back out, it can be done externally like above or internally, but until us evolution seems to only have favored better internal tools.

And not so sciency anymore, but War of the worlds Martians skip all the icky orifice stuff and mainline what they need.

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  • $\begingroup$ I came to write a similar answer. While hardly natural, there are already humans who live on a liquid diet. $\endgroup$
    – TimothyAWiseman
    Commented Mar 24, 2020 at 16:37
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A liquid diet (blood, milk, beer, soup, etc) contains a LOT of water. Vampire bats drink half their bodyweight in blood each meal and have a stomach designed to shunt water straight to the kidneys. So your guys will be peeing way more than regular humans. Unless they live in a desert and are sweating off the water instead. However they might not need to pee as much as vampire bats, since they are not flyers (a very energy demanding way to get around) and have a low body temperature (15 C). So their food requirements will be lower than a scaled-up bat.

They'll still need intestines. The intestines are for getting nutrition into the blood. Poo is what is left over - the undigestible bits which never got into the blood in the first place. The urinary tract is for getting waste out of the blood - all the metabolic byproducts produced by your cells and dumped in your bloodstream.

If you just want one 'channel' for disposing of waste, then give them a cloaca, like birds, reptiles and monotreme mammals have. Technically speaking all these animals have multiple channels (reproductive tract, digestive tract, urinary tract) but all three have a single communal exit.

They won't have teeth! There is nothing in their diet which needs chewing. Whether that gives them an appearance like a baby before its teeth have come through, or like a granny who has taken out her false teeth is up to you.

If they die of infection a lot, better hope someone invents milk pasteurisation to kill off bovine tuberculosis in your world!

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The problem with a liquid diet is macronutrient (protein, fat, carbs) density is really low compared to solids, and some things (types of fibre) are insoluble. I don't see a 2m+ humanoid surviving on liquids alone; the constant intake of food is typical of a sessile or browsing/grazing animal.

Edit:

The only way I see around this is a diet of specific liquids that have been designed or evolved specifically to be consumed by this species into and through adulthood, which again seems unfeasible without magic playing a role.

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  • $\begingroup$ I made sure to point out that evolution isn't a deciding factor. $\endgroup$
    – Fayth85
    Commented Aug 25, 2016 at 17:15
  • $\begingroup$ @Fayth85 I must have missed it. Edited. Ultimately though, if magic exists then the answer to every "can this...?" question is yes, because magic. $\endgroup$
    – rek
    Commented Aug 25, 2016 at 17:45
  • $\begingroup$ Hence the 'reality check' tag. The only cop out I'm allowing 'magic' for is evolution. $\endgroup$
    – Fayth85
    Commented Aug 25, 2016 at 17:58
  • $\begingroup$ Evolution is magical/incredible enough in real life. All known vertebrates poop or pee or both. But birds don't "pee" a pure liquid waste. Some bird droppings are very liquidy (like pigeons), and they do indeed excrete all of their waste "via one channel" (as the original question put it). Sharks too. So you could reasonably invent a humanoid species with similar avian digestive system. $\endgroup$
    – Xplodotron
    Commented Aug 25, 2016 at 20:43

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