Since I'm not getting a lot of biology-based details here, I asked over here instead.

(Original question follows...)

Here's a somewhat odd question that got me thinking lately... would an alien be continent (able to control their voiding), and would this be innate or learned?

Why does it matter? Well, debates about how continence works in humans aside, this is definitely something that can vary! Pierson's Puppeteers are stated to be naturally incontinent, and there are terrestrial species such as rats that are incontinent. At least one story (sorry, don't recall the title offhand) has postulated that humans, under the right circumstances, would not learn continence. (I would guess that most marine animals are also incontinent, because why would they need to be otherwise?) On the opposite end, some carnivore species such as cats are born "hyper-continent"; they need help from their mothers to void at all.

Ignoring societal factors (i.e. focusing on a species' pre-sapience starting point and/or what we might expect would happen to an individual "raised by wolves"), what factors would influence an organism's level of continence, both at birth, and learned as the organism matures? Again, I'm looking for whether they would be 'naturally' continent (e.g. most predators) absent the pressures of 'civilization' as opposed to not caring, rather than whether they are capable of learning continence. I'm also looking particularly at what change, if any, would occur as the organism matures from an infant to adult.

Note 1: I'm looking for a general answer rather than one for a specific species, both because that will be more useful to others, and because I do not have a single species for which I would like to know. However, if additional focus is required, feel free to restrict answers to land-based vertebrates. I'm also looking for non-opinion answers backed up by trends seen in terrestrial animals, hence the use of science-based. (So, for example, my "knee-jerk" answer would be that carnivores are born hyper-continent and learn what we would consider "human-typical" continence, while herbivores are born and would remain, absent "artificial" influences, incontinent. However, is this actually justified by terrestrial biology, or is it, if you'll pardon a more-appropriate-than-usual expression, a load of manure?)

Note 2: To clarify, what I mean by "continence" is the typical ability of an organism to consciously control when and where the it voids — "psychological" continence, if you will, as opposed to "physiological" continence, which would be whether or not the organism is physiologically capable of such control (which most animals are, barring health issues or other physical abnormalities). Using Puppeteers as an example again, they possess the physiological capability (as evidenced by Nessus and others that interact directly with humans), but most lack conscious control, and so by my definition are (psychologically) incontinent.

Note 3: As far as trying to answer this question, I should note that humans training an animal would constitute "societal factors", which I'm asking to ignore. (In short, if I add a societal desire for continence, then physiological continence will almost surely result in psychological continence as well. Again, my objective is investigating continence before — hence my focus on how continence is affected by maturation — or in the absence of such factors.) That said, AlexP makes a pertinent point, which is that we can't really know whether a non-sophont is physiologically continent. However, I believe an educated guess can be made based on whether individuals are observed to "be discriminating" in where, when or how they choose to do their business. Cats are an excellent example of animals which do exhibit such behavior, while rats are a good example of animals which do not. I would expect that comparing the behavior of infants to adults would also be informative. (I would also argue that this is what makes this a world-building question as opposed to a straight biology question. For real animals, it may well be impossible to say, but for aliens created by a writer, obviously said writer can make a decision. The goal of this question is to obtain evidence from the real world in order for such a decision to be informed rather than just "whatever the author feels like".)

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    $\begingroup$ No, I think he means what he says... Continence as in "not needing diapers" $\endgroup$ – Henry Taylor Apr 6 '20 at 15:32
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    $\begingroup$ +1 Interesting question. I don't have the science to answer it but my first instinct would be to investigate why rats are incontinent. There must be some evolutionary advantage which has split them from the mainstream. As omnivores, they are like us, mixing the predator's need to hid its presence with the herbivores need to fertilize the land. But unlike us, they are scavengers and carrion eaters. I'm betting that these are the sides of their nature which has led to incontinence. Neither their native environment nor their (dead) prey mind fecal odor, so why bother to contain it. $\endgroup$ – Henry Taylor Apr 6 '20 at 15:43
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    $\begingroup$ The equivalent of human psychology is called ethology in other animals. For obvious reasons, we cannot say anything certain about the mental life, if any, of non-human animals; it is not clear what you mean by "conscious control" in non-human animals. As far as I know, all mammals which are not too stupid (and don't have physiological restrictions, such as rabbits) can be potty trained. $\endgroup$ – AlexP Apr 6 '20 at 19:39
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    $\begingroup$ I'm voting to close this question as off-topic because: question isn't about world-building per se and has recently been duplicated (sans "aliens") over on Biology.SE (biology.stackexchange.com/questions/92477/…) $\endgroup$ – elemtilas Apr 7 '20 at 20:22
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    $\begingroup$ I'm voting to close this question as off-topic because We answer "specific and answerable" questions, must include specifics to judge "What will make one answer better than another?". We don't answer non-specific qustions which " I do not have a single species for which I would like to know" - limiting to "all land based vertebrates" is too broad. An "educated guess" is out of scope with using the science-based tag. $\endgroup$ – Tantalus' touch. Apr 7 '20 at 21:07

Continence is important to predators and territorial non-predators to be able to mark territory. You can't pee to assert dominance if your bladder has been dribbling the past few hours, the tank is empty.

It is important for prey animals so as to leave fewer clues to be tracked with. Urine and feces are both powerfully odoriferous. To void your bladder or bowels at an inopportune time is to send up a gigantic alert to the immediate vicinity "there's meat somewhere close!".

Additionally, urine can be a sexual signal among Earth vertebrates. Both male and female pheromones are occasionally present, and a female can advertise that she is in heat and receptive to mating. It's not difficult to imagine the same being possible for a hypothetical male animal (that it is receptive, not that it is in heat). For highly selective females, it might make sense to withhold that signal until the male has been vetted.

Finally, some herbivores are known to (in specific scenarios) consume their own feces. Rabbits are the most well known, but other rodent-like animals also do this. It's theorized that this is a source of nutrients produced by their gut bacteria, but since they lack the more sophisticated digestive system of ruminants, it needs to make a second trip through. If the aliens had some similar mechanism, then again, it might make sense for them to be continent... don't want to lose the good stuff while you're running away from the Venusian T-Rex.

The lack of these factors or similar won't necessarily result in incontinence, but continence wouldn't be selected for without some mechanism like the above.

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    $\begingroup$ "Theorized"? AFAIK, not only is this widely accepted, such critters pass two distinct types of droppings, only one of which is reingested. Combined with their diet and non-ruminant digestive system (this is their version of chewing cud), it's hard to believe this isn't how things are supposed to work. That said, would you assert that Niven's Puppeteers being incontinent is — can't get over how appropriate the expression is 😉 — a load of fertilizer? $\endgroup$ – Matthew Apr 6 '20 at 16:48
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    $\begingroup$ Niven deserves many different sorts of criticism, but I don't think that's a valid one. Everything I've said is very circumstance dependent. If the main branch of animal(-like) biology on Pierson's planet did not develop strong senses of smell, then prey animals might have no evolutionary pressure to be continent. Continence is a quite useless feature otherwise (until civilization, where it has some maintenance value... fewer janitors are needed, but I doubt evolution could care about such things). $\endgroup$ – John O Apr 6 '20 at 19:01

I figure it would be a matter of brain power, mobility, safety as a youngling, and cleanliness. So if they're not big enough they can't. If they are able to move around from birth and don't get left in one place, they probably won't develop it. If they're mobile, but carried by members of their family at a young age, they probably will. If they have a den that scents could lead predators to, they will.


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