Imagine a world where a creationist situation holds: God (or an alien master species, if you prefer) created all the species you see in the world today, and there will never be any others.
Are there any real world, science based mechanisms that could prevent evolution, and allow this world to persist without speciation? I want to avoid continuous intervention by the creator.
This question was inspired by Would there be evolution on a perfect world?
The simplest way would be to prevent mutation and modify sex (you do not need sex in the world, but if you must...) in such a way that, for example, the male contributes nothing except the initial stimulus (which makes this essentially parthenogenesis, and that's why sex, or better, gender is not mandatory - you always can have homosexual intercourse as a matter of course, as it happens with Eric Flint's gukuys in Mother of Demons).
All individuals are XXY triploids, and inactivation of the Y chromosome happens "at random" (this allows any ratio of male to female, depending on the probability of inactivation). XXY genotypes have male phenotype, XXy genotypes are naturally female. This kind of genetic setup is perfectly possible and naturally occurs (except for the parthenogenetic reproduction twist) in humans, where it is an anomaly. But there's no reason for it to be.
All creatures would then be identical clones genetically, but could (and probably would) sport differences, even large ones, due to epigenetic factors.
Also, depending on what the cue actually is, it might pose an interesting problem for birth control. Since all the needed machinery is self-contained in the female, sex for nonreproductive purposes could in effect be made impossible (meaning that any intercourse results in conception), or so awkward as to negate any recreational value, which might appeal to both deities and advanced aliens.
This removes most mutations due to recombination between different DNA sets.
As to how to prevent other kinds of mutation, the DNA helix gets routinely unwound and split in order to allow cell duplication. There already are enzymes that correct some common DNA replication errors. "All" that would be needed would be a super-enzyme, which we could call DNA-reed-solomonase :-), capable of detecting errors and either repairing them if possibile, or otherwise triggering the cellular self-destruct mechanism.
Such an enzyme could never have evolved (naturally), but a sufficiently advanced alien Seeder species might not find it difficult to build it from scratch.
A possible side effect would be longevity, perhaps even immortality, and complete immunity to most forms of cancer, not unlike the aliens in Asimov's Hostess.
Another effect would be a strongly reduced capability for the species to cope with environmental changes through natural selection and random mutation. This might be no great problem for a technological civilization, but for 99.999% of Earth history, it would have been a sure ticket for racial extinction.
(@Peteris's objection)
Yes, and on a cell-by-cell basis, it will often do just that.
But the "mechanism" is not a simple reasonably-soft-fail enzyme system such as evolved creatures possess. It is rather a designed computer program implemented with amino acids.
First of all it would have to fail in a zygote, otherwise the host would only get common cancer, and anyway the mutation would not get inherited.
Then, by definition the change would need to break the main cellular repair mechanism, and the organism has no others. God or our aliens never saw the need for them, and actually had a good reason not to provide them: we want defective cells to die.
So this pro-evolutionary change would actually be counterevolutionary, since it would expose the host to all kind of cellular damage against which it would have no resistance. Given the rate at which random mutations would occur and accumulate during its early development, it would be extremely unlikely that a mutated foetus could even come to term.
We (the aliens or god) can further improve our game in two ways. One: since the child is a genetic clone, we need no placental barrier. The foetus is inundated by the mother's enzyme in addition to its own. This has no effect on perfect replicas, but mutated children die stillborn.
Two: the planet itself could be abundant in any one of (or several) mutagenic compounds or phenomena (UV radiation, natural radioactivity...). Protected individuals get no cancer, while any unprotected individual will quickly develop several.
To have a mutation in the enzyme, a point mutation or even a series of point mutations would not be enough. We'd need for the enzyme to change in such a way that some further mutations will be permitted, while oncogenic ones will still get eliminated.
This is on the same scale of an English spell checker that somehow gets corrupted during the copy, but its SHA256 hash remains the same, and the resulting program turns out to not only still work but to have become a working German spell checker (I've heard this kind of hypothetical occurrence be referred to as a Minerva mutation, from the Roman goddess that was believed to have sprung, already adult and clad in armour, from Jupiter's head).
Chances of a Minerva event are in theory not zero, but I feel they're vanishingly small. This species' designers would have worried much more about the possibility of, say, a Chicxulub impact.
This is a bit of a hen and egg problem, so let's see it in practice.
Our alien engineered DNA can be represented like this (actual order is not important):
[H][CHECK][ BODY ]
where BODY is the DNA required by the cell, CHECK is the DNA that codes the "compare to plan, then repair or kill" mechanism, and H is the "plan" hash.
The CHECK part translates into a very large molecule (megaDalton range) with helicase capability, a sort of specialized polymerase. The molecule attaches to a DNA strand and "walks" through it generating a hashing/correcting bubble. At the end of the process it has calculated the DNA "hash" and compares it to its expected value; if the check fails, cellular death is triggered. At any one moment every DNA molecule in the body could be examined by up to a dozen such correctases.
A random mutation can then occur in one of three places:
But the main problem here, which would make it impossible as a natural occurrence, is that since every cell is routinely drenched in the correctase produced by itself and its immediate neighbours, any lessening in any one cell's correctase lethality would avail nothing. The cell would still be killed by its neighbours.
To survive, all cells must be mutated (or synthesized) in the same way, all at once or after being kept separate. Or you need to have a single cell with no neighbours. Even the zygote cell is not "alone", it is connected to the mother organism.
This is @MikeNichols' conclusion, and from the above scenario I would conclude that he's wrong... except he's not. He would be (of that I'm quite certain) if the organism existed alone, in vacuo. But no organism ever exists in an ecological vacuum (the closest approximation I'm aware of are Leo Frankowski's Mitchegai, an eptalogy euthanised in 2004).
And the correctase mechanism is expensive - it needs specialized machinery that has an operating as well as a replication cost. A sizeable organism would have no trouble in keeping up the whole show, but a micro-organism would be hard pressed to do the same. So our alien engineers may have stopped evolution in higher organisms, but they can't reasonably stop evolution in microbes. And as far as we know, without a (healthy) microscopic biota, life is not possible.
So we have a life pyramid where the top 10-15% is immune from evolution, and the lower organisms are free to evolve. While the middle layers may still be controllable by the 15% nobility, I suspect that a good 50% of the total planetary biomass would be logistically unreachable.
And let's not forget that this setup is the exact opposite of biodiversity. Sooner or later some pathogen will evolve that finds a suitable pabulum in those perfectly engineered, static, possibly unageing higher organisms, and will kill them all. Won't they develop genetic immunity? Well, any other imperfect organism very likely would. But the Creators made sure this couldn't happen...
There are three features of a system that are both necessary and sufficient for evolution to occur. These are heredity, variation, and selection. Any system which has these 3 features will have evolution and any system lacking any of these 3 features will not have evolution.
Variation is the existence of meaningful differences between entities in the system.
Heredity is the capability of those differences to be inherited when an entity reproduces.
Selection is the influence of these heritable variations on the fitness of the entity.
In any system with these three features variations that confer a selective advantage will be inherited at a higher frequency, which will result in a change in frequency of the variations amongst the entities in the system.
In a system lacking variation there can be no differences between the entities and therefore no selection is possible. In a system lacking heredity the selection of some variants over others has no impact on the frequency of variations in the system. In a system lacking selection there can be change due to random chance, but there will be no productive change only random fluctuations.
I’ve intentionally used ambiguous language because these rules do not just apply to biological evolution, but to evolution in all possible dynamic systems.
To address the question directly, removing any of those features of the system will suffice to prevent evolution. If your organism doesn't pass on its mutations, or if it never mutates in the first place evolution will not be possible. One caveat is that even without selection, genetic drift will still occur. Simply due to random chance some variations will be favored over others and changes will gradually accumulate. Any reproductive isolation will therefore result in eventual divergence and speciation. This gradual, random change fits the formal definition of "evolution", but I don't think most people would really consider it as such.
Sure. You'd need a new biological paradigm where children are randomized instead of combining traits from their parents.
For example, imagine if, when two humans have a child, it's basically a random human child with no direct relation to the mother or father. Your Creator figure would need to define the boundaries of randomness, while also preventing mutations.
This eliminates evolution because the fitness of a parent won't impact the fitness of a child.
A couple of notes:
Just eliminating mutations isn't sufficient to prevent evolution entirely, as species would still specialize based on fitness within their current genomes.
You would still see extinctions, and this would cause species to expand into areas they might not be optimized for. For example, say if a scavenger species went extinct. That opens up an ecological niche, and you would see a non-specialized species start to take advantage of that energy source. They wouldn't be good at it, of course, but it would still happen.
There are a lot of people in the world who believe that God created this universe, and they also believe that God drove evolution. There are several sub-schools within this paradigm and this is no place to discuss them in detail.
There are a several possibilities for a world where creatures exist and evolution is absent. The first prerequisite is what you have already provided: that such a world has been created as-is by some supreme authority. The same supreme authority can change the rules of the game and make them unfavorable for evolution. It is quite simple. It is rather a thing of theology and philosophy than science.
The flaw in your reasoning is that you want the rules to stay the same, and yet the product to be different. You want the same scientific rules which apply on this world and yet you want evolution to not occur as it does here on earth. You cannot have both of them simultaneously. You will either have to let go of the laws, or you will have to allow the laws to take effect authoritatively and drive the processes as they drive on earth.
If you change the rules accordingly, you can get a static world. We are talking about a world where:
Creatures do not compete within the same community, nor with other creatures. (That is, natural selection is off)
Neither males, nor females have any favorite characteristics about the other gender so that an short giraffe would have as much chance of mating with a beautiful female as a tall, handsome giraffe. (Hence sexual selection is off)
There is not the least random change in the dna of organisms at all. If there is any change in the dna of an organism, that organism instantly dies. (So there is no chance for mutations).
Climatic conditions have no effect on animals and neither is any animal able to correspond accordingly to environmental changes. So that animals migrating from warmer to colder regions simply freeze to death, instead of undergoing any changes that help them survive there. (Thus phenotypical changes cannot occur)
With an ecosystem running the above mentioned rules, evolution would not occur.
I think its possible to conceive of an all powerful creator that can design a non sapient species which can propagate itself without evolution as long as the creator is able to hold all environmental constants constant, such that evolution to handle unexpected environmental situations is not required. This creator would have to be magical since I do not believe that such a creator could obey they laws of thermodynamics at all.
So first answer: If you have a creator not bound by thermodynamics you might be in with a shot.
So can a magical creator define a world in which there is no evolution but that otherwise obeys known laws?
If you have sapient tool using species with free will as part of this question then even if they cannot biologically evolve, the exercise of the creator is probably doomed as soon as the intelligent species are able to begin to craft their own destiny. This happens when:
These two basic traits of a proto-technological species introduces variables that the creator cannot plan for at the outset. Social consciousness and culture - that accumulation of collective knowledge and patterns - can evolve similar to biological evolution. This is as bad for the creators designs as biological evolution.
Second Answer: If you have sapients in the world then the creator would be forced to intervene at some point even if biological evolution is not operative, and to intervene increasingly often as the evolution of the sapients ceases to be biologically driven and is now cybernetic, technological and memetic.
I think that what I have just said is exactly the cultural framework on which all our religions are based...
You'd have to take away the sapient's free will to make this work (which is essentially what Tolkein did with the Elves in Middle Earth, in order to ensure they would experience unchanging immortality and cultural stagnation).
It would have to be a world that is very stable, since one of the benefits of evolution is adaptation to change. No adaptation, then if things die, most of the rest of the ecosystem will collapse.
Swallows primarily eat mosquito (at least in MN), and if the mosquito population was mostly eliminated, even if only for a season or two, the swallows might collapse or die out. This is an extremely simple example, however it is meant to prove a point. Making changes in one place causes stresses in another. So we go through a mini ice age or a hot spell, it changes the environment and what plants and animals can survive there. If they can't adapt they will die out. It happens all the time, and without evolution, nothing will evolve to fill in those gaps that are left.
So to even think about stopping evolution you need to stop change in the world. Or you need to have an organism that is infinitely mutable to handle living in any possible environment available.
Record the genomic boundaries of the target species and devise technology to eradicate all deviation.
Clarification of the mechanism by request, presuming this is a fictional or future worldbuild:
Some self-maintaining or self-replicating means (nanotech or biotech) exists to identify and eliminate all genetic deviation. This means might be administered willingly, e.g. to all females of a xenophobic or fervently religious species, or unwillingly, e.g. by a one-time intervention of an advanced foreign agent and resident in the atmosphere. The influence might be at conception, at birth, or prior to puberty. The mechanism itself might even be a genetic trait, provided it includes backup mechanisms which are highly resilient to coding errors. The mechanism might prevent conception, abort pregnancy, terminate life, or sterilize the "mutant".
All of the above scenarios meet the currently-stated OP requirements, as of this writing.
This easily defeats the target effect of evolution, since now the "fittest" are those that are unchanging. The correctly design mechanism would require deviation larger than that which evolution itself provides, to overcome.
The answer is an emphatic No, for very basic reasons. This is a variation of @Youstaf's argument:
"The flaw in your reasoning is that you want the rules to stay the same, and yet the product to be different."
The key issue is that evolution is not a theory or a scientific concept. It is, in a very principle way, another word for reality. It means that everything just flows and arranges itself, unattended, through spontaneous events (think atomic level) and interaction within the framework of space and time.
Your setup introduces a creator, or "god", which by definition is almighty; in the presence of a god anything is possible, including, for god's sake, no evolution, if you must. But it would mean that reality is not what we think it is but that instead "god" controls everything on a sub-atomic level and what we see are actually only Potemkin's villages. A Simulacron 3, a total Truman Show, a Matrix.
I understood your question differently: "God" sets up a stage (reality functioning as we understand it, plus some mechanism X to prevent evolution) and then retreats, letting things play out. With that premise, "evolution" (of species, the universe) of course continues to happen, despite all efforts -- just, possibly, locally, slower. But, for example, at some point our sun will burn out.
There is a last, perhaps even more fundamental issue, which resembles Richard Dawkins' god critique: Even if "god" manages to halt evolution on earth, and maybe in the galaxy, "god" and our reality are still part of a larger reality, i.e. part of a larger evolution. "God" will evolve, too! She might, for example, become bored and flush this reality down the drain, or be reprimanded by the ethics committee at her insititute and decide to let evolution, i.e. "reality", flow again.
If you can do it, it will only work in the short term. No matter what precautions you take, chunks of genetic material will start reproducing and evolving outside your anti-evolutionary framework and become viruses. They will then wipe out all of your other species, since they can't evolve defences against the viruses.
Problem: How do we allow inherited individual variation (eye colour, colour-blindness, etc.) without gradual change in the species as a whole?
Solution 1: Strict mate selection
For example, elephants will only mate with a partner that is sufficiently elephant-like. Also, they will only mate with partners that are clearly very selective about whom they mate with.
But what about mutations that change an elephant's conception of what classifies as an elephant? Well, perhaps those parts of the elephant's DNA are subject to very strict quality control (e.g. checksums).
Solution 2: Species DNA
In this case, all members of a species have identical DNA, and individual variations are inherited through other means (such as epigenetics). The DNA must be copied exactly for an embryo to form.
Of course in both of these solutions, the proportion of individuals with particular characteristics within a species may change (e.g. certain eye colours may become more common over time) but the species themselves will not drift.
Evolution is a long process, but each step is based on a tiny mutation.
The mutation spreads in the genetic pool if it's a positive change for the specie, and a positive change can be :
(If i forget something, please add in the comments)
To prevent evolution, you could stop mutation.
Sexual reproduction provoque mutation. Make all your creatures some clones and you will slow evolution down (even if it might not be stopped, even with parthenogenesis small mutation occurs)
Interspecies DNA exchanges cause mutation (bacteria and viruses in your body are currently playing with some of your cells DNA, yuck). Very hard to stop, but it is a God's work. Here is a totally imaginary biology. Make viruses and tiny life forms very stable, or their DNA code very different from the "big" creatures, or make each cell inpenetrable to other forms of life.
If you don't want to change the whole world biology, try to make evolution unuseful
Have a very stable environment. You don't want species to evolve, even a little bit, because the summer was very hot and dry and this year's young frogs resist a higher temperature.
Make your creatures' life a paradise. Evolution usually makes life longer and more secure. Without predators, less selection. Without diseases, less selection. With every creature equally healthy and beautiful, no partner selection (again with the clones). The more humans make their life confortable, the less they evolve. They are no more selected by predators, diseases or disabilities. "Bad" genes do not disapear, "Good" ones do not offer a significant advantage on the number of childs to change the whole specie.
Make each kind of creatures very numerous. A tiny mutation is more likely to drown in the genetic pool of a very large group of creatures.
Bonus : now you have to find a way to keep a fair amount of creatures on your planet. Either they all die from age, or they live very long and have few children, for example ?
Conclusion your god have a lot of work to do during the creation if he wants to relax later. Evolution is a lazy but effective solution. But if you really have a god's power, you could just create a kind of creatures that eat or kill everything that doesn't fit the plan. Like a robot with a database of all living creatures. If this chicken does have more than 1% difference with the registred DNA code "chicken", kill it.
A world without evolution is going to be impossible if there is heredity and variation (as in the answer by Mike Nichols).
However this doesn't mean that your creationist forces can't be actively manipulating evolution to prevent speciation. You've just got to work out where this balancing selection is going to come from.
Speciation is generally caused by barriers to reproduction of any kind. For example two populations on different continents are likely to diverge as they can't meet to interbreed. To fix this your anti-evolution forces could be moving organisms between continents to maintain geneflow and homogeneity.
If you want to stop drift or selection within a population you could selectively remove (e.g. kill or sterilise) organisms that are distant from the population average in any trait. This helps both to remove variation and to select strongly against divergence.
No
Here's why.
Mistakes get made and creatures change over time. Even living fossils like Coelacanth who from outward appearances still look the same as ever have had their DNA change over the millennia.
So get rid of DNA.
A world of replicating robots, some species are clever and make tools which gives them an advantage over others and they quickly wipe out other species. Other clever species start altering their behaviour to avoid getting killed by the tool using clever species. Can you say that these species haven't changed? Compare this to cicadas in the real world. Are the ones that come out every 17 years the same as the ones that do not?
So make em dumb, all they can do is replicate themselves exactly and die.
All is fine but every once in a while there are accidents where a bot gets damaged and every once in a while it's replication code gets damaged and now those bots have offspring that are built in some fasion that outcompetes the original ones for resources...
You can't.
The reason you can't is the existence of domesticated breeds and the huge variation within those breeds. This requires all the organism side mechanisms for evolution to be in place. That leaves only the existence of fitness differences occurring in the interface of organism and environment as the final ingredient for evolution and there's no way of not having that without having a very different world.
You could have a created world without evolution but not with the creatures we see today in it.
I admit my knowledge of evolution dates back to my school days (about 15 years ago) and seems theories have changed in the last year. But from what I recall evolution is something "random": one day an individual is born with a different (random) characteristic, due to the again random(ish) combination of its parents genetic material. If the new characteristic represents an advantage in the current environment the individual will survive and pass on its characteristic.
However, I started to think some of the changes are too advanced or intelligent to be just the result of a chance. A friend suggested that cell are intelligent enough to trigger the changes (according to him we alter our DNA during our life). If this is actually the way evolution works, you may have your god creates all beings without this "intelligent adaptation" skill.
Keep "armless" mixes (change of traits due to mix of DNA materials, e.g. blond father + green-eyed mother = blond, green-eyed child) to avoid clonation, but remove adaptation changes (e.g. people move to colder area, skin cells "decide" to produce more/thicker hair).
