In my world, there are three species from the Homo genus that make together a clade called "aquatic humans": merfolk (Homo maritimus) (their scientific name means "marine human"), giants (Homo maximus) (their scientific name means "tallest human"), and ogres (Homo obesus) (their scientific name means "obese human") (they are still humans, just not Homo sapiens). All these species have a seal-like blubber, also, merfolk have webbed toes, and webbed fingers (I want to go on a realistic way).

They are much more likely to be autistic than anatomically modern humans (Homo sapiens): one ogre out of 9 is autistic, the same thing can be said to one merperson out of 5, and one giant out of 7 (in comparison, only one anatomically modern human out of 44 is autistic: https://worldpopulationreview.com/country-rankings/autism-rates-by-country).

Also, both ogres and giants are as solitary as orangutans, and merfolk are as solitary as blue whales (which are less social than most other cetaceans), but ogres are as aggressive as great white sharks, giants are as peaceful as gorillas, and merfolk are as peaceful as capybaras (which are nicknamed the world's friendliest mammal).

Finally, ogres have a better sense of eyesight, and hearing, but a worse sense of smell, giants have a better sense of hearing, and touch, but a worse sense of eyesight (they are as myopic/nearsighted as dogs), and merfolk have a better sense of smell (they can smell underwater like star-nosed moles), hearing, and eyesight (they can see ultraviolet light thanks to a gene derived from OPN1SW also known as short wave sensitive opsin, so they have four cones instead of three), but a worse sense of touch.

So, I wonder why would some species from the Homo genus be much more likely than anatomically modern humans to be autistic.

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    – L.Dutch
    May 22 at 11:06
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    – Daron
    Jun 19 at 9:22

4 Answers 4


They Serve a Critical Function: Culture.

The nature of the critical function should probably somehow relate to the common feature that these three races have in common: isolation. All three species obtain some significant benefit from a high percentage of their population being autistic.

A small group/isolated species is not going to have most of the advantages that are derived from the Homo group, namely cooperation. Cooperation allows all sorts of benefits, like transfer of knowledge and culture, specialization of tasks, and the members protecting and caring for each other to overcome difficulty. It's hard to even imagine humans of any variety doing well without cooperation.

In highly social human society, the relative disregard for interaction makes autistic people more likely to isolate. But in the highly separate cultures of these people, it works the opposite: They don't care if others of their species are around, allowing them to function in larger groups. So mer/giant/ogre communities would be almost exclusively populated by autistics.

The Autistics provide a workaround. In each culture, these individuals are sacred. They aren't threatening to such solitary creatures, and are thus approachable. Their autism manifests in deep memories, savant-level skills, and obsessive story-telling. So wandering or monastic autistics are the cultural glue that holds these societies together. They allow preservation of technical skills and production of goods that would normally require great skill and technology. Even the ogres don't feel threatened and want the skills and knowledge these non-threatening ones preserve.

In fact, it might even be a cross-cultural practice. An ogre seeking knowledge of water might seek out merfolk autistics, for example. So the sacred nature of these individuals might provide a sort of exchange and trade network between these very solitary and disparate groups.

Those seeking "blessings" would bring "offerings" of food and resources, and in return receive trade items or crafted/manufactured goods. The autistics are cared for, the population benefits from trade and skilled craftsmanship. Win-win.

  • $\begingroup$ "But in the highly separate cultures of these people, it works the opposite: They don't care if others of their species are around," Oooh that's a nice point. $\endgroup$
    – Daron
    May 20 at 9:22

No specific reason is needed, they are or aren't.

To support that, it possible to look at any mammal - they do have brains, and some cognitive abilities. Many of them have problems to communicate with each other, or some being hostile to each other protecting their territory, except times of reproduction. They do have repetitive interests - sleep, eat, sleep, eat etc.

ASD is a disorder only when you have something different to compare with, when it is a minority cases of a different brain wiring and develolment - only then it becomes deviation or disorder, but it could be relatively norm for ancestor species.

If we take look at monkeys, which mature in a year or few, and compare them with humans - chimps do outperform humans on certain tasks(observing) and if they could they could say humans have ASD or ADHD as we can't perform such tasks. We can't perform such tasks as children and adults, so we just can't but still(they have more developed in a sense visual cortex, so it not necessarly a thing we can learn, they wired a bit differently). (They count all kinds of objects below 10 a few times faster than we do, some japan research park with chimps, there was a video on youtube, in a sense certain observation skills of theirs are superior to ours).

It just that our development has a path further to maturity of a typical human, compared to chimps, and the path is different from others and has different treats, and we have different other capacities. And if we look at monkes it is them who have ADHD in their behaviour and ASD(maybe).(really just watch observe their behaviour, the way they use tools, sticks as an example, there are videos on youtube)

Any disorder humans have, as long as it does not endanger surviviability as a species, in some conditions, it can be a valid ending point of brain development. We call something disorder because it is a deviation from typical what we have, but by itself it is not something objectively bad or insufficient for main goal - survivial. What may be "second grade" for us, could be godly gift to others.

I mean brain we have in the way we have, more or less an exception(look at all the others mammals), and if brains of others have something we would call a deviation or disorder for ourself, can be a typical case as long as it is capable to serve the main goal - survivial. Barin themself, and behavior, and nuances can be any as long as that survivial is there.

Some behavior can be better for survial, and we outperformed(or rather our ancestor species, and not knly because of brains but because of luck too) few other branches which existed at the same time and had contact with each other.

And it has to be understood, that the fact we outperformed someone of our kind at survivial does not necessarly mean we outperformed it by intelligence, maybe those we outperformed(just my fantasy, and it possible disprove it, not sure about it) those other guys were in sculpting and painting or wood carving like Michelangelo but it wasn't time for that - it was time to eat whatever one could find, time to kill etc. It more like a note, and expansion of initial statement saying brains can be any, have any feature.

If I return to OP situation, when it is a percentage and when it has something positive, and if I let's say will be blunt, then - for a stupid species having higher ASD percentage first of all does not affect them that much, does not make a big difference, and it can be a positive because of "restricted or repetitive behaviors or interests". They have not that much brain capacity in a first place and retan attencion is hard for them, a monkey uses a stick for 5 seconds and then it is forgotten in the span of next 15 seconds, a monkey forgets it, it has no interest to that tool anymore, it does not explore its potencial beyond the moment it used it.

One who would take it more often, use it more often on a longer time frame may be building up mucles, and reflexes and expand uses of a stick, in a sense conducting exploring resears task about that stick, making random discoveries. I would not be suprised if all that started from something like that for us.

It took million year or so to get to stone tools and chipping stones - carrying using stones could become a habbit, but chipping it really requires some obsession. And because one can teach another, or be taugth just by observing others then it does not matter if other side had ASD - whatever, just invent. Modern folklore of that kind is a mad scientist. So being able to focus, some degree of obsession helps in some cases(and is a problem in other cases) - it can be curse and blessing at the same time.

And for a species member being randomly obsessed with something over and over again - can be, and maybe was the way to conduct research and development process - until they become smarter.

So asking why is a little bit incorrect way to look at that, but one of many many more potencial answers could be - they still in process of reducing the percentage(if at all) which is left fro previous develolment stage, and speed can be any, it depends, are there some other useful associated behavior (there are for some in some cases) etc. Science one of the fields to focus on - imagine 10% ppl being mad scientists - I guess we would time travel at this point, lol, not mentioning bending the galaxy inside out(or die out as a specie).

  • a general answer could be becuse it is beneficial in some way for group and society, had few examples, and it can co-evolve futher, so it has not to be a thing to be abandoned. And I would say we call severe cases as a disorder, but milder ones or even lesser ones do play their role in our society and in our development, they are ther, all over the youtube, lol, (diy community?? Lol)

All in all it a bit more complex than just call things a disorder, it needs to understand why we do so, and that brains and behaviors is a wide range of as animal and insects show it to us - those all are ways wich eligible for survival. And different patters can come because of different ways to develop them. And even if we know, have an example to compare to, to say that something is worse for this or that, it does not make that other thing bad in the other curcumstance, until those two are in direct competition.

Society/groups as buffer plays a big role as here as well, but it big topic. So just find something good to have, it has not to be a good for all 100% of the cases but if it good in 1% cases, good for society/group - it can make a huge difference. I mean things are more complex and more flexible that it seems you think they are. Just find something good, blow it as big as you like - done, you have your why reason.


Reading @Goodies comment, which reminded me, unfortunatly can't answer in the comment section, this comment reminded me about a channel, ...Gamers... something something (can't look it up atm, but maybe someday I'll put the link) - there was a guy talking about ASD if I recall correctly, and putting a theory/explanation(he has some background for that) that there are 3(or more, do not recall) behivor patterns which by itself aren't that bad, and not so bad as combination of 2 but when one hits all the marks it may become a problem(or may not, depends how strong each factor is, external conditions and external requirements for an individual etc). And brain as a whole can be seen as a combination of many such islands(patterns), which influence each other which then manifests itself in a behaviour of an individual. Some is learned, some is inherited, some is result of environment etc etc. So having a percentage of something out of place for complex enough net of those "islands" is not suprising, even if that something is not beneficial, but it can be just unlucky combination of otherwise beneficial things. I really have to find that channel, seems it is exactly what OP has to listen to, to get a better picture.

  • 1
    $\begingroup$ +1 good read.. I can add ASD means Autism Spectrum Disorder. There are many behaviours pinpointed in the definition, you can't pinpoint a single "autism" issue in the spectrum and then simply assign "autism" to go compare to others. Sapiens, Maritimus, Gigantus and Obesus will each develop their own type of ASD that "covers" a particular behaviour in the spectrum, applicable for that group. You have a valid point. Even among humans there could be types of ASD that cannot be seen, because they were never recognized "issue". $\endgroup$
    – Goodies
    May 21 at 10:39


All three species are solitary. It makes evolutionary sense they would not have as developed a social structure as real humans. There is no need to be as good at reading faces or judging subtle social cues or dealing with large crowds.

This frees up areas of the brain for other things like hyper focus and staying up all night to memorise the script of Deep Space Nine Season 4.

I especially like the episode where everyone wants to go out with major Kira.

enter image description here

There she is. None of the boys can resist. They like her because she has short hair and spunk.

To get back on point, having too many people with Autism is selected against since it makes it harder for a tribe of early humans to function. If your species have smaller tribes then the selection is not so strong.

Though if the giants and ogres and mermaids are sufficiently alien, it is a moot point whether their "autism" is the same as our "autism".

  • $\begingroup$ DS9 is not as good as Voyager. Fight me. $\endgroup$
    – Daron
    May 20 at 12:59
  • 1
    $\begingroup$ Am I sensing a Kira crush? Well, it's not like anyone on the worldbuilding site knows anything about autism, is autistic, has kids who are autistic, nephews who are autistic, ... $\endgroup$
    – DWKraus
    May 20 at 18:52
  • $\begingroup$ @DWKraus I had just watched Season 4 "Return to Grace". One of the best episodes, and everyone in it fancies Kira to boot! I guess that makes me too! $\endgroup$
    – Daron
    May 20 at 19:22

Intestinal microbiota

It is commonly, but erroneously, said that people are organisms of the species Homo sapiens. In reality, a large body of research has illustrated that a "person" is a community of organisms, and that the single-celled organisms of the gut affect basic medically measurable aspects of personality, including "autism, anxiety, obesity, schizophrenia, Parkinson's disease, and Alzheimer's disease."

In your scenario, humans have moved away from a traditional lifestyle into many new biomes and diets. In this process, there has been a major change in the organisms within the intestine, causing whatever alterations you need to explain.


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