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Yes, I KNOW that evolution is a process that occurs through many generations via random mutations and natural selection, but in a world where humans have found a cure for aging and have mind backups in case of unnatural death so very few people bother to reproduce, what would be a plausible way to make humans evolve by changing their own genome in response to environmental changes through positive and negative feedback, thus increasing their advantageous characteristics and decreasing their disadvantageous ones and achieving """natural selection""" in a single individual, something beyond mere acclimation or even epigenetics.

(This is not the focus of the story so it doesn't need to be super detailed, because of course if it needed to be detailed you would be better off just writing a scientific paper and win a Nobel Prize.)

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    $\begingroup$ It looks like you're asking us to brainstorm and generate ideas about some technobabble and handwaving to explain something fantastic in your world. Such questions have answers that are entirely based on the subjective opinions of the answerers and are prohibited on this site, for a multitude of reasons. $\endgroup$
    – sphennings
    Jul 19, 2022 at 18:35
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    $\begingroup$ All this already happens, it is called acclimation, things like tanning, making more red blood cells at higher elevation, muscle growth, ect. $\endgroup$
    – John
    Jul 20, 2022 at 3:16
  • $\begingroup$ well, completely handwaving it (like star trek does) is the only way to go here. $\endgroup$ Jul 20, 2022 at 8:58
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    $\begingroup$ Sounds like you want to take a page out of the cephalopod skillset. We already know of species of squid and octopus that edit their RNA in order to respond faster to changes in their environment, which ironically enough may or may not cause their actual DNA to change at a slower rate. Also if your humans have finally gotten the technology to achieve lobster status, taking other "superpowers" from other animals, such as the superb immune systems found in certain bat species, would certainly not be that big a stretch, not when somehow no one aging anymore is very real. $\endgroup$ Jul 20, 2022 at 18:12

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It appears what you want is a humanity that stops aging but, in every other respect, continues on as it normally does. While that's going to cause all kinds of problems (like wealth distribution, property ownership, even the nature of crime...) simply taking aging out of the mix...

...changes nothing.

I understand that you're proposing that whatever it was that caused the "cure" to aging somehow also stopped the evolutionary process. It didn't. Or, more accurately, it needn't. It's your world so you can do what you want. It only causes a problem if you think it does.

Impeding the aging process needn't, and IMO factually wouldn't, change how evolution works

I believe you're operating on several false premises.

  1. If my aging stopped in my 20s, that would NOT be a reason to stop having sex. Quite the opposite, I assure you. Well... unless I got bored of it, but the biological imperative that drives human sexuality isn't tied specifically to aging. So it wouldn't stop. What would happen (unless you declare otherwise) is that women will stop having children after their eggs have all been deposited. So unless you have a cultural reason (e.g., a legal or religious prohibition) against having children. You're still going to have children.

  2. You're also going to have death. A lot of people certainly die from old age. But a lot also die from disease, accidents, crime, war.... And nothing would drive war more than an infinitely increasing population on a world with limited surface area. So, you have babies being born and people dying. On an evolutionary time scale, what's changed? Pretty much nothing.

  3. You're also ignoring the reality that change can come from all kinds of sources. Chemicals, radiation, weather exposure, accidents.... People less prone to succumb to those issues are more prone to pass on their genes. That's evolution.

Conclusion

I don't think you need a new explanation to justify natural selection or evolution at all. You've removed one aspect of it, but only one, and it doesn't have the species-ending consequence you're suggesting.

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    $\begingroup$ You mention women running out of eggs. I would say this, if nothing else, would be a great incentive to occasionally procreate! If all humanity's women would end up without eggs, we would be a very fragile species! $\endgroup$
    – EdvinW
    Jul 19, 2022 at 22:12
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Frame change, don't change genetics so much as expression levels and switch controls that is change the epigenetics.

Genetics are flexible.

Genetic information as run through cell processing machinery can do many things.

Most people are not albino and have melanin production. There is a default set from birth base level of how much to produce then there is some variable on top that(tanning) based upon exposure. An adequate system if person live close to where there ancestors did.

Want to control expression levels.

What is required is not so much evolution as ability to control expression set points. ie a person who is traveling around Arabian peninsula would would to have high melanin levels, then would want to turn the melanin production down when they go to Germany for a few months in the winter.

The trick for melanin control is to control expression levels of melanin.

Switch control

It would be possible to say have the genes for both red and black hair. Then if there could be a switch so that when hair is being produced it would take path red or path black depending on switch value. This is what happens in calico cats except for some cells are on the 'red path' while others are on the 'black path'. The desired is to be able to switch this on demand for all cells.

Some changes more permanent

Some adaptation will not be able to be undone such as the tendency for people growing up in cold environment to have shorter limbs and people in growing up in hotter environments to have longer limbs. Altering limb length is much more difficult.

Switching method / Epigentics

More genetic information can be present, it just required method to allow switching either of the type use this section rather then that section. Or to be able to dial production up or down depending on desire.

This is done via whats known as epigenetics. Where and how to control this precisely is an active area of research. Generally by methlylation of various parts of DNA

Hypervisor - ultimate solution.

What would truly be the solution would be to have hypervisor mode where a person could mentally enter a mode where they could change their settings. This is what Ian Banks' Culture civilization has access to. they have enough control that they can switch to male or female, grow wings, switch on drunk setting etc.

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The mechanism you are looking for already exists, it is called Gene expression. Genes can be switched on and off depending on the external conditions.

That would be a limited evolution because it will allow people only to use old features that are already encoded in the genome, but will still allow some degree of adaptation. The rest will come the usual solutions used in the past 10000 years. Use a little bit of creativity to invent dresses, prostheses and tools to extend our body.

The really big change would happen if people managed to be more flexible with attitudes and beliefs, after all the bigger changes we have seen in the last 2/3 thousands years come from cultural evolution rather than genetic evolution.

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It is easy to imagine the presence of some sort of McGuffin gene that results in relatively slow variation of an individual's genetic code in some of their cells - You could add a second McGuffin process that copies 'good' mutations across to other cells, or alternately allow the body to become chimeric, with improved kidney genes only found in the kidneys and good muscle genes found only in some or all muscles.

But the problem is in determining what factors provide the 'feedback' signal to determine if a gene is beneficial or detrimental.

In a population and in normal evolutionary development, the feedback is purely and simply based on success at passing genes on to the next generations - more or less by definition a 'better-adapted' individual is one who has more reproductive success. In addition it needs a large number of 'trials' via numerous individual's success/failure to filter out the random noise that more significantly effects the reproductive success of individual animals.

In your scenario you have to choose some other mechanism to determine adaptive success, and there lies the problem. Your genetic mechanism could make tiny random changes in genetic code and 'watch' for feedback in terms of physical health, or stress levels, or (at a stretch) happiness - but there is an awful lot of noise in the signal - are you (un)healthier because of the change in some gene related to digestion or because you ate lots of vegetables or got food poisoning? As a result of the very low signal to noise ratio there would probably be more random genetic drift than ther would be beneficial changes in any single individual - even over thousands of years.

In addition, unless the feedback system is very 'clever' then, even if it does succeed you may not get what you want. Even 'natural' survival-of-the-fittest evolution shouldn't be considered as a path to higher quality. Lets say the McGuffin relies entirely on bodily health - you may end up evolving you brain function so you are adapted to be ultra-paranoid about any external dangers. You live like Howard Hughs in insane isolation but keep safe from germs. Or say you use happyness as your trigger - you may 'evolve' over time to be happy but really stupid.

About the only way I can see this working would be if the genetic changes were consciously chosen. So either the individual can look through a catalogue (maybe from GenesRUs Inc. or iGenes Ltd.) and 'purchase' improvements in heart function or memory retention - if that is what they want. Or there is some sort of embedded AI process that does the same thing for you.

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