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I am writing a story where a species undergoes devolution. Is there any scientific or plausible way to do this? The process can be instantaneous or may take ages, I do not mind which as I need to weigh my options at this stage.

To be clear, the devolution I am thinking of is like taking a human being then devolving him/her to the primate stage, so lets say about as far back as Orrorin tugenensis or Paranthropus where they are in the midst of evolving from primates to Homo erectus. Please note I used human beings as an example to give context but the species undergoing devolution may not necessarily be human.

Based on the answers, "devolution" does not exist so had the word in quotes to reflect this.

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    $\begingroup$ Evolution (in any paradigm) doesn't happen to an individual. It happens to a population over time as a result of selective breeding favoring favoring specific traits. "Devolution" is simply natural selection that favors traits that were previously selected against. $\endgroup$ – pojo-guy Apr 13 '18 at 1:53
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    $\begingroup$ Humans cannot (d)evolve into primates because humans actually are primates. Specifically, humans are apes. More specifically, we, together with the orangutans, the gorillas and the chimpanzees, are great apes (subfamily Hominidae). $\endgroup$ – AlexP Apr 13 '18 at 2:26
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    $\begingroup$ There is no such thing as devolution in biological perspective, in fact decreasing complexity has been seen as part of evolutionary traits in many species. Unfortunately adaptation is not a measure of success because fossil record shows that at certain period of time almost 90% of all species becoming extinct. $\endgroup$ – user6760 Apr 13 '18 at 2:47
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    $\begingroup$ I get what the OP means, but let me compare: Evolution is a bit like acceleration in mechanics. Things don't decelerate, they accelerate in the opposite direction. $\endgroup$ – phresnel Apr 13 '18 at 7:23
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    $\begingroup$ Watch the film Idiocracy and understand that devolution is well underway. $\endgroup$ – Sentinel Apr 13 '18 at 9:20

14 Answers 14

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Devolution doesn't really ever occur, organisms simply adapt to best suit their environment over time. A good example is cave dwelling Troglodyte type species that have lost the ability to see. They haven't actually devolved to not have eyes, they simply did not need them and evolved to save valuable energy and nutrients by not growing a sight organ that would be useless in their environment. It isn't devolution, its still evolution since they are changing to better suit their environment. So, at least as far as natural processes go, a species would need to become stuck in an environment for a few hundred thousand years that heavily discourages intellect, sociability, communication skills,culture, and inventiveness. That's a tough one to come up with since such traits are usually the most powerful ones for surviving something.

So here's the environment and scenario I'm thinking of. Your smart guy race is in the stone age, its pretty much on par with homo sapiens and where they were at about 10,000-15,000 years ago. But something catastrophic doesn't happen. The world slowly becomes a perfect Eden with very few predators, a perfect climate, and vast endless fields of grain and forests of fruit bearing trees. No ice age, no super-predators like we saw in said ice age. No famines or depredation, no rabid competition between several human subspecies for the same resources. The planet (Henceforth known as paradise) is literally perfect. Too perfect. Why would a species that has as close as possible to absolutely nothing to worry about need to even develop the ability to worry? Those big craniums and complex brains waste space and make childbirth more dangerous than necessary. There is absolutely nothing gained by possessing speech, abstract thought, or cooperative culture when all a species needs to do to be successful is to wander around placidly in small familial groups grazing mindlessly on the limitless amounts of food. Shelter is utterly not necessary since you have a perfect climate, nor is clothing, and food is so ludicrously plentiful there is no need to make tools. Within another 100,000 years your species that was formerly well on their way to developing things like agriculture, warfare, and tribal societies has reverted back to dumb grazers that simply live to eat and reproduce.

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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Apr 18 '18 at 3:18
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Breed them to match sub-optimal traits from previous generations.

I recall a clever plot device in the Xanth series where a curse (you can substitute magic for any scientific technique, such as CRISPR) was used to make a certain species of humanoids attracted only to the ugliest, smallest, most unintelligent members. Over time, these creatures got more and more hideous until an equilibrium was reached between the force of the curse driving them to poor sexual selection and natural selection killing off the less fit. The end result was the creation of goblins, small, knobby, violent, and unintelligent but numerous creatures that lived in caves. After enough generations into the curse, millions of years of evolution had been undone.

While this appears to be devolution, technically it is evolution, as these creatures are forced to adapt to the existence of a curse. Even though they were less fit than their ancestors, they still managed to find an equilibrium that gave them maximum fitness when placed in an adversarial environment (an environment with a curse that limits their sexual selection opportunities).

This actually has a parallel in mundania the real world: breeding. We can easily breed animals in a way that seems inferior to their wild counterparts, but that is still evolution because the species is evolving to survive in an environment where traits that would normally improve fitness such as viciousness instead are detrimental (because they would not be selected for breeding). While there may not have been Chihuahuas in the past, you could easily select for traits that they had long ago.

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    $\begingroup$ Real word example of such breeding - domesticated foxes: independent.co.uk/news/… $\endgroup$ – Daniel Frużyński Apr 13 '18 at 7:27
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    $\begingroup$ Breeding giant Chihuahuas would be an interesting challenge. $\endgroup$ – Thucydides Apr 13 '18 at 12:28
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    $\begingroup$ +1 as it's pretty much the only feasible way of achieving what the OP wants. $\endgroup$ – r41n Apr 13 '18 at 13:33
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    $\begingroup$ Your thinking of the goblins in Xanth. $\endgroup$ – Pelinore Apr 13 '18 at 13:56
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    $\begingroup$ @Pelinore Doesn't the post say that? $\endgroup$ – Azor Ahai Apr 13 '18 at 19:27
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As noted, natural evolution does not reach pinnacles or devolve, but rather adapts to the environment. Different environments provide different niches, an albatross, penguin and phorusrhacidae are all birds, but rather different because of the very different environments they inhabited.

If you are going to "devolve" the creature, you will need to use genetic engineering. Palaeontologist Jack Horner has been working on this, attempting to turn a chicken embryo back into a dinosaur. Since chickens are literal descendants of dinosaurs, there is nothing in principle to prevent rolling back the process of evolution and hatching a dinosaur. Perhaps it is for the best that we actually don't know how to do this........yet.

enter image description here

Perhaps a bit more tweaking

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    $\begingroup$ honestly a chicken drumstick the size of a T-rex one would solve so many bbq issues... $\endgroup$ – L.Dutch Apr 13 '18 at 12:01
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    $\begingroup$ You would need a 55 gallon drum of barbecue sauce, though.... $\endgroup$ – Thucydides Apr 13 '18 at 12:26
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    $\begingroup$ +1, that picture... $\endgroup$ – r41n Apr 13 '18 at 13:30
  • $\begingroup$ ...can't be unseen. $\endgroup$ – Jared Smith Apr 13 '18 at 17:03
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Devolution doesn't exist.

Evolution is a process that keeps going; unless you want to get deep into genetic engineering, there's no way to turn it back.

What you can do is create a situation where the best path forward is to become more "primitive", if you want to start with humans and bring them back to a primal level the best thing you can do is start removing civilization.

Give a read about humans raised by animals, without the social structure these individuals are already much closer to this primal existence.

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    $\begingroup$ Stating that evolution keeps going forward you imply there is a preferred direction. That is not the case. $\endgroup$ – L.Dutch Apr 13 '18 at 5:04
  • $\begingroup$ @L.Dutch yeah, bad choice of words, I wanted to say that it don't stop. $\endgroup$ – Sasha Apr 13 '18 at 12:42
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Devolution doesn't happen explicitly. Evolution can be forced in the opposite direction though. This could match what you intend to do.

The driving force behind evolution

For this example I am going to take resistance to antibiotics as evolutionary trait, but this is pretty much extensible to most other things.

Competition is the driving force behind evolution. In bacteria, it is a constant race to be able to divide as fast as possible. Faster than your neighbor. After all, if you grow fastest, there will be more yous.

In an environment where no antibiotics exist, the bacteria that can convert the surroundings into energy the fastest wins out. However, when we introduce an antibiotic that mimics the surroundings, but instead of being broken down, blocks the mechanisms of the bacteria, this all changes.

That efficient bacterium will not be able to divide as efficiently anymore. So suppose there also is a bacterium that has another gene that allows it to prevent the antibiotics from entering its cell. This means that in the presence of antibiotics, this bacterium has an enormous advantage, because it isn't hindered by the antibiotics and will be able to divide just as normal. This is generally how resistance to antibiotics propagates through the population of bacteria.

So what about "devolution"?

There is one important piece here. Resistance to antibiotics isn't free. In this example it is producing some protein that blocks antibiotics, in another example it could be a modified protein that isn't a viable target anymore to antibiotics, but in (almost) every case, this resistance has a cost. Having to produce a protein, having a less efficient enzyme, and so forth.

This doesn't matter in the presence of antibiotics, living is more important than that bit of energy. When there are no antibiotics however, these resistant bacteria are at a disadvantage. They are expending energy for something that has no benefit for natural selection anymore. The effect is that the unresistant bacteria will be growing faster and thus will be selected for.

So what does this have to do with devolution?

You can interpret this as devolution of the species, because the selecting criterium has been removed/changed so that what was selected for at first, is no longer useful. This doesn't immediately mean that that trait will be explicitly selected away, but given that most traits like this cost energy, if they are unneeded, they will eventually disappear.

As another example, there are plenty of species that at some point in their evolutionairy tree had limbs, but developed in such a way that they did not need them anymore. Take whales for example. We know they have had limbs at some point, because there still are rudimental bonestructures looking like limbs. They have been evolved away though. There was no need for them, so there was no driving force preventing mutations that lowered effectiveness of these limbs. These traits might even have been beneficial, as growing limbs costs energy. Energy better spent growing fins for example.

So to properly simulate the "Devolution of a trait or species", it is important that the selecting factor (if there is one explicit factor) is removed or made redundant.

Important to note here though is that this is mostly devolution from the perspective of a certain trait, like legs. First legs evolve, then they evolve away again. This happens. Species turning back into older species is much less likely, because it is so many traits that have all changed, that would have to be selected against suddenly.

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This is possible (to some extent) if your population is small enough through inbreeding:

Inbreeding results in homozygosity, which can increase the chances of offspring being affected by recessive or deleterious traits

You would still have to make a plausible case for

  • losing specific traits that would have to disappear in your scenario, e.g. intelligence, manual dexterity;
  • but not to the extent that the species would die out.

Since evolution is unpredictable I think you can make it plausible, if you can find a reason why the population size has dwindled. Decreased intelligence would be the important factor IMO.

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You could introduce a dominant genetic disorder that causes this "effect of devolution" over time, like a degenerative disease. For example, if the creatures have big ears because hearing is important, the disease might make their ears smaller and so on. Bipedal creatures might have a spinal problem that makes them more curved and prone to rest their arms on the ground as quadrupedal. A genetic disorder can be manipulated any way you want to achieve any effect you desire.

If the creatures are not advanced they would not be able to understand the cause and will simply keep breeding and with each generation the condition might aggravate. If they are advanced, you need to figure out ways why they wouldn't research and avoid passing the gene on.

The important thing to bear in mind is that a species that do not adapt to their environment tend to go extinct, so at some point this should be the outcome of their "devolution", unless there are some other circumstances at play that might allow them to live even when unapt.

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  • $\begingroup$ Evolution works over generations. As you correctly pointed out those unfit to the environment reproduce less (or not at all). Without reproduction (d)evolution cannot happen. $\endgroup$ – L.Dutch Apr 13 '18 at 11:26
  • $\begingroup$ I pointed out that the more inept a species is, the harder it is to survive, but I didn't say that they reproduce less. They might reproduce the same, but if the group is getting smaller than of course each generation will have less population. But that could take many generations to happen until extinction. $\endgroup$ – Paula Hasstenteufel Apr 13 '18 at 11:52
  • $\begingroup$ Upvoted for actually attempting to answer the question! $\endgroup$ – barbecue Apr 13 '18 at 15:36
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Evolution is change. The reverse of change is still change.

In simple terms, evolution is just random mutations appearing in offspring, and some mutations carrying a greater chance of spawning progeny.

There are some widespread misconceptions about evolution, based on misinterpretations and half-truths. These are wrong:

  • Evolution can happen to a living individual.
  • Evolution causes individuals to change to adapt to the environment.
  • There's some natural ranking of evolution, where birds are the "better" version of dinosaurs.
  • The genetic code of "previous" species is somehow stored in the "advanced" species.

If you're willing to ignore realism, you can pretend these are real. Or you could introduce a variant setting where they are real. Or you involve god and creationism, and write god's rules.

Other alternatives are:

  • Have selection pressure that prefers individuals who are similar in some aspects to the species you want them to look like.
  • Have aliens/gods who kept notes of the previous mutations, and who now undo the previous mutations one generation at a time.
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Evolution is basically, in simple terms, “A bunch of tiny changes”. If an organism has a bad change, it dies. If it’s a good change, it lives, passing on the DNA. Hence, evolution. What you (could) do is change the DNA of an embryo to match that of a primate. It’s less of “devolution” than directly changing the DNA to copy a primate... more or less giving the desired result. (Hope I helped :p )

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Look up the most recent information on Homo floresiensis -- currently thought to be a group of Home erectus who were isolated on an island and adapted to suit the conditions there. In their case, it meant that individuals expressing more primitive traits (smaller stature, less calorie-intensive brains) were best adapted for the conditions at play, and over the generations their species evolved in a direction some people might consider "backwards".

Islands are great evolutionary laboratories -- you get founder effects, population bottlenecks, and a plausible way to get past relative low points in species fitness. It's pretty easy to handwave your way to the perfect environment to adapt your species in whatever direction you want on an island, and then reintroduce them later. (For example, scrub Homo sapiens off the planet with a weaponized plague spread by birds that your island group are immune to, and then some suitable number of millenia later raise up a land bridge to let them go forth and colonize.)

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It is, in my opinion, wrong to say that devolution does not or cannot occur. Evolution is a biological process that depends on selection of genetic material for propagation, where the selection depends on an ecosystem as a continuous, typical environment.

Some exogenous and extraneous occurrence, a natural disaster or intentional attack, can disrupt the process. For example, a nuclear attack that mutates all the genetic information thus far created will not result in nuclear-resistant species, but will just result in mutated species with ongoing genetic illnesses.

The way you use the words evolve/devolve though, to "devolve" a species back to being an ape would require the "evolution" of human feet (back to being hands) and the "evolution" of strength and agility. Regardless, a mechanism of achieving this in any short time frame would have to be through some kind of widespread modification of genetic information.

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  • $\begingroup$ Yes, one of the ideas I was toying with was a "DNA Reverter" which maps out your current DNA, extrapolates previous evolutionary changes and revert you back step by step in a sense. $\endgroup$ – Arkhaine Apr 16 '18 at 3:55
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You can try "junk DNA" -- inactive or non-coding bits of a genome that has many origins, some vestigial. A smart and malevolent enough virus ( or suitable nanotech ) may be able to reactive or remix that old DNA. You could also create a virus/nano that lays dormant for a long time chemically cataloging historical shifts in DNA and inferring through some algorithm where evolution did not go.

"junk dna": https://en.wikipedia.org/wiki/Noncoding_DNA

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If you are asking about devolution in terms of education and by extension intelligence, it is already happening to humans. Since educated people are having less kids, the current human evolution is optimizing less education and by extension less intelligent species. I do not think that this can devolve humans to primates. Maybe back to stone age. Most likely it will stop far before that happens.

A similar situation with more serious outcomes could happen to your species. A social kind of norm that prevents educated people to have kids can help to devolve your species. Some sort of strict policy on teachers and scientists having kids could work. This way, once the first lineage of intelligent individuals are gone, the same could repeat with the upcoming generations.

Edit:

(This part has nothing to do to answer the question, merely as an answer to the comments as these explanations takes longer than comment character limit.)

Education is closely related to intelligence. A least to a degree, the choice of having better education is affected by intelligence. Here is an article supporting that claim: https://academic.oup.com/ije/article/39/5/1362/802787 Additionally, correlation between education and childbirth is well-known, thus, the current increase in IQ depends on the increase in minimal level education (most of the countries primary school education is enforced), use of technology, better medicine and better understanding of pregnant and infant needs. Here is another article having the same conclusion: https://www.livescience.com/24713-humans-losing-intelligence.html

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    $\begingroup$ "Since educated people are having less kids"... I'd like some evidence of that claim, please. $\endgroup$ – wizzwizz4 Apr 13 '18 at 7:51
  • $\begingroup$ washingtontimes.com/news/2011/may/9/… or pdfs.semanticscholar.org/6de7/… I am sure you can find even more data on the subject. $\endgroup$ – Cem Kalyoncu Apr 13 '18 at 8:13
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    $\begingroup$ From your second link: "the better care these women give increases their children’s human capital and reduces the economic need for more children". Proof for your next claim ("the current human evolution is optimizing less education and by extension less intelligent species") please. $\endgroup$ – wizzwizz4 Apr 13 '18 at 8:17
  • $\begingroup$ I don't think you understand what evolution is. $\endgroup$ – forest Apr 13 '18 at 8:40
  • $\begingroup$ I don't get the counter point you are trying to give. Having 1 child that ends up having better education (or wealth) and thus having less child does not increase your rate of genetic contribution. However, having many less educated children that will in turn make more children will increase it. Fertility rate < 2 means your lineage will die off eventually. There are genes that controls human intelligence and tendency towards education. Thus having less of those genes in the gene pool means having less intelligent population. Please read and understand before replying. $\endgroup$ – Cem Kalyoncu Apr 13 '18 at 8:41
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I fully agree that devolution or involution does not exist, but assuming that terms like the evolution where some characteristics are lost, carrying the species to a supposedly ancestral phase (in only some aspects), then you can be better inspired by the evolution of the parasites. The extreme adaption to live inside a live organism cause lost of metabolic routes, oganalles and organs. For instance, eyes in some arthropods, the whole digestive apparatus in tapeworms, or the mitochondria in some flagellates.

But note: Two decades ago flagellates as Giardia spp. were considered «primitive» early eukaryotes because the lack of mitochondria. Nothetheless, in fact they are more evolved that us with respect this plastid. They had mitochondria, but living in anaerobic habitats that endosimbiont was transformed in another organule (mitosomes) that was not discovered until the end of the XX century. So,.. Giardia species devolved or evolved?

A tapeworm have not gut like a planarian because live inside a gut, but have hooks to anchor to the mucosa and a unparalleled multiple reproductive system produce huge amounts of eggs. Devolved or evolved?

The bee louse (Braula coeca) is a fly without wings, but it flies using bees without wasting energy. Devolved or evolved?

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