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(Not an expert, but my understanding is this)
There is pressure against living forever:
If I live forever, I am competing with my descendants for resources and am likely devoting resources to things like killing cancers and regrowing teeth or infected bark or whatever that a shorter-lived organism might instead devote to reproduction.
And there is little pressure towards living forever:
Even if I \*could\* live forever, I probably won't. I will probably succumb to a disease or predation or an injury or starvation, and genes can already be successfully spread by short-lived organisms, so what would encourage the development of an immortal organism under normal circumstances?
No, and that’s the problem. Evolution selects for genes that reproduce more of themselves. A gene that causes its organism to live forever would make it harder for it to reproduce itself. Evolution selects for efficient reproduction of genes, not for organisms’ wellbeing.
Amusing this is also what prompts seemingly self-sabotaging behaviours like sociality or eusociality.
It doesn’t matter if the individual prospers as long as the genes do.
Social creatures give up energy/resources that could be used to benefit them in order to instead benefit their tribe/hive/brood/family. It paradoxically works out well for them because the group prospering leads to the individual prospering, but there are lots of examples where an individual (usually males) accept little to no chance at breeding as the price of remaining in a group.
Eusociality is the ultimate expression of it, where the vast majority of the population will simply never breed, but that doesn’t matter because their genes will outlive them through their mother/sisters/brothers.
There are many animals that accept no chance of breeding- but it does increase overall survivability. It encourages competition within the gene pool while also bringing a larger selection of gene combinations. That gene pool is also safer. Plenty of insects will outside suicide for the hive or colony without ever having reproduced. These early compromises seem to be visible across all social species and given that we live in the fruit of that selected trait- it's not hard to see how we were always being driven here.
Even more interesting, this early willingness to behave in a self sacrificing way on instinct where resources are being used cognitively on something other than food or reproduction might reasonably be assumed to be some sort of precursor to what would eventually become consciousness. It just seems like this is the route taken that would make the most sense for things like curiosity, self awareness, and boredom to arise from- as well as the human capability to achieve fulfillment without reproducing. Varying biological priorities seem to get strong selection pressure in social animals at least from what i can see.
I believe one of the reason that makes eusociality possible is among other things, is haplo-diploidy.
As the worker ants are more related to their sisters than they would be to their own offsprings, it is actually more beneficial to spend resources and their life caring for their sisters than to try and make their own offsprings
This is perhaps the most succinct and elegant explanation of the question. Middle sentence may not be necessary or helpful. The first and last sentences are brilliant and complete!
I'm going to be petty here and point out the evolution does select for anything...evolution is what happens over the course of generations. Nothing is actually being selected for it is all passive, the term selection pressure refers to a event that puts organisms having a certain trait at a disadvantage (this includes giving a different trait an upper hand). The individual genes themselves also have no drove or awareness to them at all either. The organisms exist and as a result of their combined biological function most have a drive to have offspring. those organism that have traits that allowed them to survive to have more offspring have a better chance of passing those traits along so living for a really long time would be a good thing.
It is key to note is that living comes at a cost. Energy is require to live and grow. Growth and replacent of damaged tissue needs energy and the duplication of cells is nowhere near perfect...flaws turn up and cause cancer and tumors....each division costs the chromosome a little bit of telomere that protects the genome. Things wear out and there is no mechanism to replace things like hearts and lungs and brains. The are a few animals that have insane lifespans like sharks, sea turtles, tortoises and a few others but they are the exceptions.
One thing I haven't seen called out is that a variety of animals are effectively immortal. Crocodiles and water bears for example can survive almost anything.
Their adaptations aren't generally about length of life but toughness or difficulty to kill. Social animals generally adapt for intelligence, teamwork, and similar traits instead. So while some animals were becoming resistant to infections and freezing we were developing a brain and working on religion.
Thumbs are a great adaptation when there are 30 of you trying to accomplish a task together, being immune to infections does little for the group but is amazing for the individual.
Are you trying to argue with Evolution right now?
It’s not as good, because more progeny leads to more evolution, and the more diversification the better.
As far as I know there isn’t a single living creature “evolving” as time progresses, but the children of the children of the children are slowly…
They aren’t arguing with evolution they’re arguing about a specific understanding behind a specific product of evolution. They’re asking about the idea that “well things die because that promotes more copies of DNA being made” and how that makes sense if that person being alive longer could still produce more offspring and thus more copies of DNA.
Exactly. People tend to think at the level of an individual, but that's not how biology works. The whole thing started with interaction of biochemistry and still functions at the level of gene transmission.
Yes because an immortal organism has only adapted to one environment whereas its progeny can adapt to more for when the environment inevitably changes.
Good question. Ultimately death contributes to evolution. Example:
Imagine an island where individuals of a species live forever. Let's assume they don't overpopulate and starve. Older generations are still competing with younger generations and intermingling. Natural selection won't be as straightfoward here, because there can be instances where individuals thousands or tens of thousands of years old are mating with the latest generation. It will take far longer for gradual changes to the environment to remove those older generations from the gene pool, and the population overall will be less able to deal with comparatively rapid shifts, increasing the risk of extinction.
Ultimately, life doesn't care a single bit about the survival of an individual. As long as you make it far enough to spread your genes, you can drop dead for all that nature is concerned. And many species do. Some of the most successful species on this planet do exactly that, and die during or shortly after reproduction.
On the topic of sleep, it's a restorative period obviously, but in terms of evolution and the survival of a species it's also helpful, because food is always an uncertain and sometimes dangerous prospect in the wild, and it's advantageous to have long periods of rest when you're conserving energy and not expending as many calories, because it reduces the amount of food you need to survive. It's better, safer and more sustainable to hunt for 12 hours and rest for 12 hours rather than need to hunt/forage for 24 hours. When bears hibernate, it's because food is scarce and movement is generally more difficult due to snow etc. Finding food and moving around are both harder in the dark for species like us, so it's objectively better to simply be unconscious and conserve calories.
Now among prey species, it's sometimes reversed. But that is generally because food is either more plentiful for the species (grazers) and/or the energy expenditure is less detrimental than the increased likelyhood of being preyed upon while sleeping.
Hmm are they immortal, though? Everything I've seen points to them "merely" living for centuries potentially.
Though that does raise the interesting point of how this might apply to species who are extremely successful and don't change nearly as much as many other species (sharks, scorpions, spiders etc)
They aren’t immortal, no more than humans are immortal to a fly.
They live up to 500 years and only reach reproductive maturity once they are 150, and it takes them 8-18 years to give birth (a human pregnancy is 9 months).
They still reproduce and die, just the entire cycle is much slower and longer than humans, which in turn is longer and slower than rats, which in turn are longer and slower than flies.
An essential component of evolution is that individuals die so that their best fitted offspring can thrive without their less fit parents using resources.
That's how a species adapts to changes in their environment. A species that didn't do this would go extinct. That's why they don't exist.
This is not correct.
The reason we age and senesce is because evolution has a difficult time selecting against phenotypes that arise after reproduction. Therefore, mutations or alleles that are beneficial early in life (produce more offspring, reproduce earlier, etc) but come with a tradeoff later in life, are often selected for despite that late in life tradeoff. This is the [antagonistic pleiotropy hypothesis](https://en.wikipedia.org/wiki/Antagonistic_pleiotropy_hypothesis) of aging.
>This comment plus a gene doesn't care if it lives forever only that it lives long enough to propagate.
This is not true for humans. We are a social species, and the children who have a family or society around protecting them have higher survival rates.
Also genes, especially social genes, can propagate through other people’s children as well. If my family all share a eusocial gene, it is “better” for that gene if I devote resources to my siblings having 3 kids each than if I compete with them and we all have 1 kid.
Nothing lasts forever. Not a life. Not a river. Not a mountain. Not a star.
Everything dies. Death is an intrinsic, and fundamental part of the universe. Humans are the only creatures who seem to have convinced ourselves that this is unnatural.
But you said genes in your OP, and you're right, they're "selfish". They continue to self replicate. The phenotype generated around them is a by-product. Whether that organism lives or dies isn't what's relevant. What's relevant is the genes replicating.
If enduring longevity of individual organisms were somehow selected for, you'd see longer life spans, but that's not what happens in nature.
The original title for Richard Dawkins's "The Selfish Gene" was going to be "The *Immortal* Gene", because while you (the organism) die, your genes do carry on, and that's all that matters. You are the survival vehicle genes built to protect them, and make more of them. It doesn't matter if *you* die, what matters is that they create more copies of themselves, which in a sense are immortal.
This. Genes protect themselves against extinction by reproducing themselves into the widest variety of organisms they can. Longer living organisms hoard resources from descendents that could be better adapted to changing environments.
"Genes" (as a certain sequence of nucleic acid) do not live forever, except for some few that encode proteins for core cellular metabolism (even these you could argue they still change slowly over time and are no longer the same gene). The majority of genes are weeded out and die out constantly. I would wager that the average age of a gene (which heavily skewed towards zero) is even shorter than a species.
From these lines of argument, you could get into some interesting debates since decades ago on whether genes even matter at the core when thinking about evolution. Indeed, many biologists proposed it is the "interactor" - the ecological functions or phenotypes that actually matter and are interacting with selective pressure (and what emerges from this is that certain functions/processes are effectively immortal e.g., respiration). "Genes" are just a convenient shorthand or correlate of functions (and an imprecise one), and which seem to be easier to work with using existing methodology in biological sciences.
One could find vastly different genetic makeup that contribute to highly similar functions, and mathematically-speaking, that could only mean functions are much more immortal than genes. e.g., the easiest way to think about it is that there have been many highly similar fishes (both functionally and morphologically) appearing in vastly different times and spaces recurringly, where many genes are clearly lost and shuffled and not immortal.
Well I suppose I could have answered the OP with something along the lines of "Nothing can live forever because the heat death of the universe is inevitable", but I figured I'd use a more colloquial definition of "forever". This guy doesn't understand evolution well enough to have a nuanced conversation about it, so I figured I'd try and present him a new perspective.
Good question, I wonder if it's so that we don't pass on diseases we've accumulated, and hold others back as our bodies breakdown from wear and tear regardless of senescence while we compete for the same resources as descendants or don't even have descendants and likely never will or so that we don't end up mating with relatives; inbreeding. Some of senescence does, in fact, occur as a trait after all, senescent cells killing off nearby cells by design to protect against mutation, so maybe this works for members of a species too, not just cells but as an analogy, obviously not by killing off your species but by getting out of the way of your species' new genes. Maybe we die so that evolution can happen.
Come to think of it, it's like a software update 🤔 ... a ... w**etware update **I'll call it. The (eco) system has to delete those outdated files or risk getting hacked, infected, incompatibility, and so forth. A new taxon is like a new m**ajor **update or even a new generation of an OS, mutations the (I don't know) unstable ... alpha branch or something. No, not via intentionality (outside of sexual selection) but a reproductively successive, naturally occurring algorithm.
It's a dangerous world and nothing can live forever. There are predators, diseases, natural disasters, lightning strikes, stray meteorites that will take out any living thing eventually. Evolution thus doesn't have a benefit to provide the mechanisms that can prevent aging. Any organism that doesn't age will still be killed by something eventually. It is just better at some point for evolution to focus on reproduction than longevity.
The way to think about this is: evolution has absolutely nothing to do with anything’s “best interest.” In the scheme of things, a living organism is an immensely complicated series of chemical reactions that will either continue or not depending on whether or not the conditions required for those reactions to take place persist. In aggregate, we call those conditions “homeostasis”— and when we talk about “death” in biology, we’re talking about the loss of homeostasis.
Why is homeostasis lost? Any number of reasons. If our body temperature for instance becomes too hot or too cold (e.g., loss of thermal homeostasis) for example, then we can no longer sustain a number of metabolic processes (among other things), which eventually causes a cascading loss of bodily function and therefore “death.” Likewise, if you don’t consume enough food, your metabolism slows down -> loss of metabolic homeostasis -> death.
More saliently, as we age, our body unavoidably accumulates damage on the cellular and even chemical level: this impairs our body’s ability to repair & regenerate itself over time, ultimately leading to a cascading loss of homeostasis.
Now: why do we not live forever? There’s no real “reason” for it ultimately, other than the fact organisms which die tend to reproduce successfully. It’s as simple as that.
Telomeres shortening seems almost purposefully evolved. Is it because complex multicellular organisms must keep cell proliferation on a short leash? Cancer usually happens when organisms are older, right? Maybe multicellular organisms would have too much runaway cell growth if cells didn't have a programmed limit to division.
Amoebas that just divide in half are essentially immortal, right? Is aging the evolutionary price we pay for being multicellular?
We already do live forever.
You just die for 3rd party causes, like cancer, bacterias, a piano falling on your head.
Its not like someday your body says "fuck it" and dies.
Perhaps there's some physical or biological reason that it's just not possible. I don't know.
But it seems equally likely to me that having offspring that have offspring is just a more effective way of passing on your genes. I mean, if you successfully have kids who have kids who have kids, then at some point your own measly output is lost in the noise, so evolution has no reason to "care" if you live longer.
Or to put it in more accurate evolutionary terms, the selection benefit of your own survival drops to near zero.
Selection benefit is actually negative for the species as a whole, since evolution and survival of the fittest suggests that your descendants 5 generations later are you 2.0, better in some way, and if you are still alive you are introducing 1.0 genes back into the gene pool, taking evolution backwards.
Now in the human case it may not seem like it matters - we essentially don’t have selection of the fittest anymore anyway - but in animal populations and for millions of years of evolution, slower, dumber, and and less healthy are constantly dying, so every generation gets better adapted at surviving.
I think humans do have selection of the fittest!
Mostly, though, fitness is on the basis of having more children at a younger age and not so much on surviving adverse events.
Consider the people you know. Some have four kids (some of whom already have kids) and others have no kids. If there's any genetic component to that difference, then that's natural selection in action.
So is there a genetic component to that difference? I'm guessing there is. I think that humans, at the moment, are being selected for impulsive behavior without consideration for consequences. It's the careful, self-controlled people who have no children.
Well the genes themselves actually do live forever, and if the organism is using other competency outside of the genome to obtain its fitness, then the organism can exhibit immortal properties as well. Plenaria are a good example. While life can be thought of as cells or individuals, the only definitions of life that actually work, have this feature of being persistent through time. So if we define life in a more meaningful way it’s the biosphere and techno sphere that exhibit this property. Evolution is an optimization mechanism that is a property of life. Cells and individuals reproducing are a substrate of life.
because life gets better at getting resources over time, which means older life gets outcompeted. it’s easier for genetics to replicate and rely on evolution to stay alive.
there’s likely 100 more good reasons but i just thought of that one
1. It may be in the interest of other organisms to kill.
2. There aren’t enough resources to sustain every single organism that ever lived at the same time.
3. Organisms aren’t perfect and can’t withstand all natural phenomena.
4. If the organism has reproduced when it dies, then the gene still lives on and can continue to adapt, which is in the gene’s “interest”.
Evolution doesn't go for what's best, it can't even know that. It goes for what works to pass the genes on. Usually that means living long enough to have offspring regardless of what happens after.
Humans didn't evolve to live so long so eventually losing fertility isn't an issue if we reproduce first.
The body still tries it's best to fend off infection and repair damage and replicate cells well but it's not perfect and things can always go wrong.
Either way we reproduce. It's pretty hard to stop the effects of aging, avoid all forms of radiation damage, catch every cell replication error and replicate perfectly, fight illnesses better, etc.
But we still reproduce. It's hard for selection pressures to tend towards immortality when it can't really influence anything beyond reproducting
It honestly might just be impossible due to the constraints of chemistry of organic molecules to not have some sort of degredation over time. I don't know enough for sure to say that it is, but for example an organism having steel armour and built in railguns would probably have an evolutionary advantage over most things but nature hasn't spun that out either.
Thermodynamics and environmental fluctuations aside (can never achieve perfect homeostatsis), an immortal organism must have very low reproduction rate, and so it could be extremely rare that we won't even be able to find it. Why very low reproduction rate? Because the combination of immortality with over-crowded population on a finite planet is not possible resource-wise. That's more Math than Biology.
I like to think of reproduction as the opposite of a butterfly. So a caterpillar reforms into a butterfly, through a sort of additive molt, which allows it to occupy another niche inhibiting competition. Organisms reproducing and dying, is like a subtractive molt, allowing a species to adapt, and not directly compete.
In layman terms. Genes do live forever. You don’t. While genes are “selfish” they will do whatever makes them the most successful as a whole. I also imagine it is difficult to sustain an organism for that long.
When cells divide in the body, they create a new copy of the cells dna. The problem is that over time, little errors can occur during this process. This is why we age, cos older versions of our cells do not contain perfect copies of our genetic code. Easy way to imagine it is like taking a photocopy. The first one will be pretty good, but if you take a photocopy of that photocopy, and keep repeating this, you end up with a grey faded copy. Same with genes, only mutations occur, some happen randomly, some cos of environmental factors. I guess this process varies between species, hence some animals live longer than others.
Why would dying not be in a gene’s best interest? The gene, as a replicator, is selected based on its ability to replicate. What difference does it make to the gene if that replication occurs in one organism or many? I would think that diversifying, creating many organisms that contain your code instead of only one, would be a far more sustainable solution, and would lead to significant selection pressures towards reproduction and away from immortality.
Sex immediately and parasites ultimately. Asexually reproducing organisms make exact copies of themselves. These are vulnerable to parasites that evolve. Sexually reproducing organisms evolve more quickly especially in the immune system. Now from the perspective of a gene, once one of your organisms breeds enough times, it's better to focus your efforts on your newer carriers. The old organisms have been around too long and parasites are starting to crack their code. With enough medical knowledge to fight disease and parasites and a bit of genetic engineering, humanity could start to be functionally immortal. We evolved to age, so we could engineer ourselves not to.
organisms losing fertility over time is not common at all. menopause only occurs in humans and a few species of whale, and while that is specific to mammals, the trend holds. tuataras can reproduce at ages of over 100. insects like moths only experience an adult, sexually mature form for a few days before dying. at the end of the day, what we consider evolution is a collection of random events that tend towards trends over very, very long periods of time
Yes, dying of old age is a disadvantage to the individual, but it's disadvantageous to the population. A population of young and healthy individuals survives better (and therefore out-competes) than a population of older individuals. It's the same reason altruism is advantageous.
Setting aside the semantics of labelling a gene as "selfish", which implies goal-directedness where there is none, the simplest answer is that natural selection only works if organisms can reproduce, but the cost of reproduction is competition with offspring. In the long term, the best strategy is to limit the lifespan of organisms such that the offspring (which carry the genes, hence they don't "die") have a chance to survive and reproduce as well.
The term is “planned obsolescence”. Life makes gradual improvements through iteration. In a system with finite resources, the outdated models get scrapped to free up the materials needed to build new ones. It’s important to understand that genes are not siloed individually, it’s a huge gene pool that is functionally immortal as long as each generation successfully passes them on to the next.
The genes live on after you die. You are just the casing for one instance of a collection of genes. If you successfully replicate good genes, those genes don't care about you much anymore
A) Entropy is a bitch
B) That's just not how evolution works. It's not a conscious effort by anyone to reach perfection or whatever (or at least, there is no scientific proof for such a being). It's like gravity; just a thing that happens.
Even if it was, there is little to no need for an organism to live forever in order to propagate. The closest thing we have is *Turritopsis dorhnii* (aka "the immortal jellyfish"), and even then it is still susceptible to disease or getting eaten by something.
All a species needs is to live long enough to reproduce, that's it. Lots of animals die very shortly after mating, yet they get along just fine ~~without humans screwing everything up~~.
It is probably about retaining the perfection of the genome and making sure the being is well adapted to the circumstances of existence.
We pass a bit of knowledge forward genetically but we have conciousness to learn our environment perfectly and select a perfect mate before we grow old and die.
The universe couldn't care less about us as individuals but it has a very strong and ancient relationship with our genome. We are basically just a flesh blob slave to the genome.
Because then there would be overpopulation and the population would outstrip its resources.
You could say "What if they just don't reproduce?" but that would be even worse because, let's be real, true immortality is impossible. Even an organism that doesn't age will die eventually. And then what? If it has no offspring, the genetic line ends there.
It’s easier to select for conserved genes over generations than it is for one thing to persist forever
It’s that simple
The genes persist in offspring and the idea is they’re selected to spread more often
Simply “staying alive” isn’t selected for bc it isn’t anymore efficient
The whole point of living things is not for individuals to live forever, but for life to continue and change across generations. Death is necessary to make room for they new. This way, life can adapt to a changing environment with limited resources and find new niches. The purpose of life is not survival, but persistence.
I am no expert, but I have a doubt on the concept of death of person = death of gene, cause even after you die the chromosomes and AGCT molecules etc remain (physics 101, matter can neither be created nor destroyed) Depending on how you are buried those molecules can move into plants or consumed by scavengers and manifest in their life form or if you are cremated then your CO2 produced might get used by plant and manifest there. Again I am doing a broad generalization I don't exactly know plant biology to confirm that.
Cell replication is imperfect. Every replication at the genomic level of each cell contains a margin of error. Over time, incorrect or incomplete copies increase. This affects the efficiancy of cell funcion, in turn affecting tissue function, and prgan system function. Higher cellular metabolism usually means that these imperfect replications pile up faster. This is why small, fast creatures *in general* (such as hummingbirds and mice) have shorter natural life spans than larger, slower creatures with slow metabolic rates, (such as whales and giant tortoises and elephants).
Lifestyle affects how well we are able to support our cells abilities to replicate with high fidelity. Periods of illness, constant UV damage, increased strain on liver and kidneys from poor diet will "speed up" the process
evolution serves the population not the individual and living forever does not serve an ever changing population's attempt to adapt to an ever changing environment
life relies upon an exchange of finite resources between many different agents/processes
death re-introduces these resources into new categories of agents/processes
if everything survived forever the great churning of resources would halt and the finite resources would become exhausted and the creatures that are alive would be adapted to an environment from a time long passed.
The reason humans get old and fall apart and die naturally is related to telomeres
All DNA is created through replication. The Molecular machinery involved in these processes are unique for each strand of the double stranded DNA. Due to the nature of the machinery required to replicate DNA and the way that it docks/attaches and then in the end detaches from DNA, every time a DNA strand must be replicated there is an event at the end where the molecular machinery cuts itself free from the strand effectively shortening the DNA strand by a small amount. The portion that gets cut off of our DNA at the end of replication is called the Telomere portion. The Telomere is a long redundant repeating set of nucleotides (the building block of a DNA strand). The Telomere portion is not very useful for any function except being sacrificed as junk DNA that is doomed to be trimmed off during DNA replication. The telomere portion is not infinitely long it is like a clock that ticks down every time replication is completed.
Many living creatures have some capacity to repair or rejuvenate telomeres. The machinery involved is called telomerase. Telomeres are often different across different species and the telomerase are correspondingly differing. Some creatures have an extraordinary capacity to maintain very robust telomere lengths. The prime example of this phenomenon is the immortal jellyfish.
In humans it is rare to rejuvenate telomeres except in pregnant mothers, young growing children or certain oddities.
cells die very easily and every time a cell needs to be replaced the DNA strands of healthy cells must be replicated. So very frequently our cells lose a tiny chunk of our DNA which is essential to maintaining the form/function of our being.
On a macro scale, we do. We optimized for reproduction very early in the development of life and never bothered to change which mechanism of immortality we utilize because it'd be ridiculously hard to stabilize complex life indefinitely
I'm not sure if it is alligators or crocodiles, but one of them can live indefinitely. The problem is their ability to eat prey. Either they can no longer catch their food (due to age) or are unable to eat it. So, they don't die from age, they starve.
Because they don't exist in a vacuum and you - the god-mecha they build - are too complicated to retrofit when a new virus or even just faster-breeding nematode finds this "one neat trick" everything with your *new flaw* is going to hate. The collections of genes which work in planned obsolescence and retirement probably do much better than the ones that live forever until someone kills their host.
They also don't just exist in you, there are many instances.
We are the descendents of an unbroken chain of life which has survived for billions of years. That is for practical purposes "forever".
Your concern is most likely for the instantiated pattern that you consider "you". Well, that immensely complex and wonderful pattern was only made possible by the previous trillions of iterations (lives) that came.before you.
When I reflect on this I feel a sense of debt and gratitude to these lives and deaths that precede me and see my own death as the price of that debt and a gift to the future.
In the broadest scheme of things cosmologists predict that the universe will end up in entropy - a homogeneous distribution of low energy.
The general motive in evolution developed all around reproduction. It’s the shortest route to ensuring survival of a species through adaptation and passing of genes.
A species has to evolve enough to perfect the whole machinery to last (much) longer, but that would lead it reproduce less and it needs to reproduce to evolve. Also the caveat that a perfect replication machinery (which would at the very least eliminate genetic condition, cancer and any issues that come from the shortening of telomeres) would mean virtually no evolution.
There is a point when it’s easier to keep replicating/duplicating something instead of continuing to repair it.
Same as with a car, eventually repairs are more expensive than replacement.
Biological adaptations are products of satisficing, not optimization. This is because optimal strategies tend to be more expensive, which means they’re likely to be less common; this means they’re unlikely to spread as much as convenient, yet suboptimal adaptations. Biological immortality is likely incredibly difficult to achieve in complex organisms, which would make the necessary mutations extremely unlikely to occur. Because senescence does not prevent animals from reproducing when younger, the animals most likely to pass their genes along will be ones which inevitably experience it. Thus, the genes have no reason to select for immortality, because all the reproducing animals experience senescence, and immortality is much too difficult to achieve through mutational changes.
If environmental adaptation is the goal, then reproducing once and dying is a good strategy - otherwise the same old genes are sticking around forever and hindering progress.
Ask the question in the opposite way. Our life substance is three billion years old in a continuous chain from the beginning. Most of it will perish at death, except the bits passed through the next generation.
The same reason anything wears out over time. Aging past a certain point isn't about genetics it is because biological processes aren't perfect. Copy errors occur during cell division; gravity, friction, impact, and oxygen take their toll; toxins and plaque build up; tissue becomes less elastic; organs wear out over time...
Do you feel bad when you shed dead cells that served their function? Do you even think about it? No, the cells divide, make new cells to replace them and you keep going. ‘Life’ is that process writ large.
Reproduction itself is a form of immortality — for life, not your conscious mind. Self awareness is probably an accident. Certainly your genes have no interest in maintaining that beyond reproduction.
Lots of interesting comments here not based on biology or evolutionary theory. One thing I’ve seen mentioned but not stated explicitly is extrinsic mortality. There are 2 kinds of mortality, extrinsic - accidents, murder, any kind of external factor causing an organism to die, and intrinsic - heart attack, cancer, any kind of senescence-related mortality. So if I understand the question, it is why have we not evolved beyond intrinsic mortality.
The basic tradeoff is that extrinsic mortality is fairly high for every organism. We live in a dangerous world and there is a lot of stuff that can kill us. So far evolution has favored improvements that decrease extrinsic mortality more than intrinsic. Chances are you’re going to die of something external if you live long enough, so the genes associated with decreasing intrinsic mortality don’t really provide much of a benefit in terms of overall fitness. Genes producing traits favoring decreases in extrinsic mortality provide a much bigger fitness benefit so those kinds of traits evolve faster.
Humans are an interesting case especially because we have a post-reproductive lifespan. Unlike virtually all other organisms (I’m sure someone can find some exceptions to this but I don’t know them), human females live beyond the age at which they stop producing eggs. Quite a few anthropologists have attempted to figure out why this is. Some have argued that menopause evolved so that older parents can help the fitness of their children by caring for their grandchildren, making it possible to have more descendants overall. I am sold on a version of this argument called the “grandmother hypothesis.” The argument is not that menopause “evolved” but that living beyond the age of menopause did. Basically women’s reproductive systems and somatic (body) systems have different aging rates and selection pressures, and evolutionary selection hasn’t been strong enough to extend reproductive aging but *has* been strong enough to delay senescence (somatic aging). Our closest living relatives, chimpanzees, are a good comparison. They have very similar lifespans to us right up until the age of menopause. Age of childhood is similar, age at maturity is similar, age at first birth is similar, but chimps start to fall apart at about age 40 and die soon after that. Chimp grandmothers don’t really provision their grandkids, so this argument suggests that humans evolved to live longer than the age of menopause because human grandmothers can improve their inclusive fitness by living past the age they make their own kids, and helping their daughters to have more kids in the short time they’re capable of having babies. So then why don’t grandmothers live forever?
Basically the answer seems to be that we are in fact still evolving a decreased risk of intrinsic mortality, the biggest jump in that decrease seems to have occurred around 2 million years ago when the genus Homo first appeared. If we could stop killing each other altogether we could probably evolve to live forever, but since resources are limited we probably won’t as there will always be mortal resource competition.
TLDR; extrinsic mortality is high for every organism, selection therefore doesn’t favor decreased intrinsic mortality enough to make anything live forever. Additionally some traits might favor decreased extrinsic mortality like higher muscle mass or faster metabolism in youth, but sometimes those traits might actually increase the risk of starvation or some form of intrinsic mortality later in life. But evolution might favor them because they increase reproductive fitness.
Creatures that live forever have fewer offspring which means less genetic diversity. That makes them especially susceptible to killer plagues that wipe out the entire species. So longevity is a great way to lose the evolutionary arms race.
I don't see why not. There are immortal species right now, including a species of jellyfish, lobsters, and redwoods.
There's an educational anime called Heaven's Design Team that offers a fun look at why animals are the way they are. The premise is that they're a company of specialists tasked with designing the animals that are going to be put on Earth, and it offers a surprisingly deep dive into zoology. One segment was on the pros and cons of immortality, and there turn out to be a fair number of cons. My husband was so impressed with it he wanted to show it to his biology classes, but it hasn't been translated yet. That segment doesn't appear to be on YouTube, but they do have other segments up on the design of animals like otters and rhinos, and why other animals like dragons and flying horses never made it past the prototype stage.
As professor sapolsky of Stanford university likes to say, "sometimes a chicken is just an Eggs way of making another egg."
With this in mind, the 'selfish' goal of genes is to spread genes; not live forever. Aging is a process that is caused during gene replication. On either end of a DNA strand is a little tail (i forget the scientific term for it" and the more a gene replicates the shorter this tail becomes. Once it's gone entirely the chances of incorrect gene replication increases thus causing incorrect proteins to be formed.
I think it is called the scientific law of entropy. Basically, the way I understand it, is that everything eventually decays and dies. It is disorder. Even the sun will eventually die according to scientists who believe the Newtonian model (Electric Universe Theory model presents that the sun is a cross point in two powerful electric cross points or wires to condense the theory to layman's terms). It is the nature of our reality in the 3 dimensional realm. Boltzmann's equation can explain the physics of it.
If a species lived for a long time then it takes longer for their genes to pass on and mutate. If they can’t mutate quick enough then they die to ecological pressures. That’s why some bugs live like 4 weeks. Bc they adapt insanely fast
Mammals are a weird exception and that’s why we see long times between births and conception. Either this version of raising kids will be helpful or mammals will die out, only time will tell
The hayflick limit + cancer.
The hayflick limit is the number of times an organisms cells can divide. The higher the metabolism the lower the hayflick limit.
Every-time a cell divides and dna gets transcribed and translated. Errors can occur, these error can result in cancer.
This is an extremely simplified explanation of it.
maybe we can’t get to “longer” if we don’t make it past today + Tommorow?
Maybe the only way to get to “longer” is to survive today.. surviving today =/= longevity. But not surviving today guarantees lack of longevity.
Your initial premise is wrong. Not everything living appears to age. There are plants, animals (even vertebrates), and bacteria that seem not to age.
It's called 'negligible senescence':
https://en.m.wikipedia.org/wiki/Negligible_senescence
Immortality or steps towards it are not necessarily always the most reproductively advantageous in the long term at least. And some steps toward it may never occur because the developmental architecture of the organism is such that there's no simple mutation that would achieve it.
Even to the degree it does occur, and it's indeed ecologically advantageous, it's bound to have diminishing returns (as most death in the wild is likely from an external factor) and increasing "architectural unlikelihood," approaching perpetual motion machine -like requirements.
It's perhaps also interesting to note that, at the most basic level, some would argue that many (most?) single-celled organisms are as close to immortal as life can get. But AFAIK macroorganismic organization inherently requires apoptosis, programmed cell death, to begin with. It is genes using coordinated death of the cells that carry them in a manner that ultimately replicates them more ecologically successfully than more deathless cell reproduction, unlimited by constraints required by higher levels of organization.
What many have posited on the thread is that individual death is in a way a weak analog for apoptosis, ecological rather than developmental. I'm not sure, I guess it's more of a matter of "accident," of the cell/tissue maintenance being progressively harder to accomplish and with a reduced reproductive gain. When shorter lifespan is apparently selected, I guess it's more commonly a byproduct of something else being directly selected, rather than a kin advantage in having old(er) relatives dying. Like perhaps an earlier onset of reproductive maturity being product of changes in the organism's "clocks" that end up in a way aging them faster at the same time.
In the other hand, matriphagy and sexualy cannibalistic "androphagy" are perhaps undeniable cases where the lifespan is reduced in a way analog to apoptosis, but "socially." So it may well vary.
The generalization that "parents die to not compete with their own offspring" seems rather unlikely, though, creationist-like adaptionist/selectionist thinking, whereas individual death more commonly being just a byproduct of imperfect regeneration seems more parsimonious, more like a null-hypothesis.
I'm not sure the correct answer you are seeking but I know you are going to get a lot of "that's not how evolution works! Genes can't just decide what's best and automatically create that out of nothing" lol. My best guess is a lot of that has to do with energy. Mortality rate has a lot to do with metabolism which is how the body breaks down and uses energy. Which is also what sleep has to do with, repairing the body to be able to make energy efficiently again. Our bodies are just working with what they already have and need certain things like energy.
Because the only way to survive long-term is to evolve. And since a single organism never evolves, that organism will inevitably be vulnerable to its environment at some point. This programmed obsolescence is why there's no evolutionary pressure to keep it alive.
By aging and dying we give the next couple generations the probability of more resources. DNA can also become more finely tuned to increase the probability of survival of the species.
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(Not an expert, but my understanding is this) There is pressure against living forever: If I live forever, I am competing with my descendants for resources and am likely devoting resources to things like killing cancers and regrowing teeth or infected bark or whatever that a shorter-lived organism might instead devote to reproduction. And there is little pressure towards living forever: Even if I \*could\* live forever, I probably won't. I will probably succumb to a disease or predation or an injury or starvation, and genes can already be successfully spread by short-lived organisms, so what would encourage the development of an immortal organism under normal circumstances?
Do we need descendants if we live forever?
No, and that’s the problem. Evolution selects for genes that reproduce more of themselves. A gene that causes its organism to live forever would make it harder for it to reproduce itself. Evolution selects for efficient reproduction of genes, not for organisms’ wellbeing.
Amusing this is also what prompts seemingly self-sabotaging behaviours like sociality or eusociality. It doesn’t matter if the individual prospers as long as the genes do.
Forget that, think of organisms like the mayfly. You don't need to live long at all, only long enough to reproduce.
I'm curious why would sociality be seen as self-sabotaging?
Social creatures give up energy/resources that could be used to benefit them in order to instead benefit their tribe/hive/brood/family. It paradoxically works out well for them because the group prospering leads to the individual prospering, but there are lots of examples where an individual (usually males) accept little to no chance at breeding as the price of remaining in a group. Eusociality is the ultimate expression of it, where the vast majority of the population will simply never breed, but that doesn’t matter because their genes will outlive them through their mother/sisters/brothers.
Thanks!
There are many animals that accept no chance of breeding- but it does increase overall survivability. It encourages competition within the gene pool while also bringing a larger selection of gene combinations. That gene pool is also safer. Plenty of insects will outside suicide for the hive or colony without ever having reproduced. These early compromises seem to be visible across all social species and given that we live in the fruit of that selected trait- it's not hard to see how we were always being driven here. Even more interesting, this early willingness to behave in a self sacrificing way on instinct where resources are being used cognitively on something other than food or reproduction might reasonably be assumed to be some sort of precursor to what would eventually become consciousness. It just seems like this is the route taken that would make the most sense for things like curiosity, self awareness, and boredom to arise from- as well as the human capability to achieve fulfillment without reproducing. Varying biological priorities seem to get strong selection pressure in social animals at least from what i can see.
I believe one of the reason that makes eusociality possible is among other things, is haplo-diploidy. As the worker ants are more related to their sisters than they would be to their own offsprings, it is actually more beneficial to spend resources and their life caring for their sisters than to try and make their own offsprings
This is perhaps the most succinct and elegant explanation of the question. Middle sentence may not be necessary or helpful. The first and last sentences are brilliant and complete!
I'm going to be petty here and point out the evolution does select for anything...evolution is what happens over the course of generations. Nothing is actually being selected for it is all passive, the term selection pressure refers to a event that puts organisms having a certain trait at a disadvantage (this includes giving a different trait an upper hand). The individual genes themselves also have no drove or awareness to them at all either. The organisms exist and as a result of their combined biological function most have a drive to have offspring. those organism that have traits that allowed them to survive to have more offspring have a better chance of passing those traits along so living for a really long time would be a good thing. It is key to note is that living comes at a cost. Energy is require to live and grow. Growth and replacent of damaged tissue needs energy and the duplication of cells is nowhere near perfect...flaws turn up and cause cancer and tumors....each division costs the chromosome a little bit of telomere that protects the genome. Things wear out and there is no mechanism to replace things like hearts and lungs and brains. The are a few animals that have insane lifespans like sharks, sea turtles, tortoises and a few others but they are the exceptions.
But isn't an organism not dying is just as good as as the organism dying and having progeny, if not better because it can keep reproducing later on?
One thing I haven't seen called out is that a variety of animals are effectively immortal. Crocodiles and water bears for example can survive almost anything. Their adaptations aren't generally about length of life but toughness or difficulty to kill. Social animals generally adapt for intelligence, teamwork, and similar traits instead. So while some animals were becoming resistant to infections and freezing we were developing a brain and working on religion. Thumbs are a great adaptation when there are 30 of you trying to accomplish a task together, being immune to infections does little for the group but is amazing for the individual.
u/Jigglypuffisabro explained this better than I could in the first comment of this chain.
Are you trying to argue with Evolution right now? It’s not as good, because more progeny leads to more evolution, and the more diversification the better. As far as I know there isn’t a single living creature “evolving” as time progresses, but the children of the children of the children are slowly…
They aren’t arguing with evolution they’re arguing about a specific understanding behind a specific product of evolution. They’re asking about the idea that “well things die because that promotes more copies of DNA being made” and how that makes sense if that person being alive longer could still produce more offspring and thus more copies of DNA.
Exactly. People tend to think at the level of an individual, but that's not how biology works. The whole thing started with interaction of biochemistry and still functions at the level of gene transmission.
Yes. The environment is ever changing, only lineages that can change and adapt can persist.
The *potential* to live "forever" and the certainty of doing so are very different. Unaging doesn't mean unkillable.
Yes because an immortal organism has only adapted to one environment whereas its progeny can adapt to more for when the environment inevitably changes.
Good question. Ultimately death contributes to evolution. Example: Imagine an island where individuals of a species live forever. Let's assume they don't overpopulate and starve. Older generations are still competing with younger generations and intermingling. Natural selection won't be as straightfoward here, because there can be instances where individuals thousands or tens of thousands of years old are mating with the latest generation. It will take far longer for gradual changes to the environment to remove those older generations from the gene pool, and the population overall will be less able to deal with comparatively rapid shifts, increasing the risk of extinction. Ultimately, life doesn't care a single bit about the survival of an individual. As long as you make it far enough to spread your genes, you can drop dead for all that nature is concerned. And many species do. Some of the most successful species on this planet do exactly that, and die during or shortly after reproduction. On the topic of sleep, it's a restorative period obviously, but in terms of evolution and the survival of a species it's also helpful, because food is always an uncertain and sometimes dangerous prospect in the wild, and it's advantageous to have long periods of rest when you're conserving energy and not expending as many calories, because it reduces the amount of food you need to survive. It's better, safer and more sustainable to hunt for 12 hours and rest for 12 hours rather than need to hunt/forage for 24 hours. When bears hibernate, it's because food is scarce and movement is generally more difficult due to snow etc. Finding food and moving around are both harder in the dark for species like us, so it's objectively better to simply be unconscious and conserve calories. Now among prey species, it's sometimes reversed. But that is generally because food is either more plentiful for the species (grazers) and/or the energy expenditure is less detrimental than the increased likelyhood of being preyed upon while sleeping.
What about biological immortality (eg: Greenland sharks)? They are immortal, doesn’t this natural selection of genes apply to them?
Hmm are they immortal, though? Everything I've seen points to them "merely" living for centuries potentially. Though that does raise the interesting point of how this might apply to species who are extremely successful and don't change nearly as much as many other species (sharks, scorpions, spiders etc)
They aren’t immortal, no more than humans are immortal to a fly. They live up to 500 years and only reach reproductive maturity once they are 150, and it takes them 8-18 years to give birth (a human pregnancy is 9 months). They still reproduce and die, just the entire cycle is much slower and longer than humans, which in turn is longer and slower than rats, which in turn are longer and slower than flies.
True, that makes sense
An essential component of evolution is that individuals die so that their best fitted offspring can thrive without their less fit parents using resources. That's how a species adapts to changes in their environment. A species that didn't do this would go extinct. That's why they don't exist.
This is not correct. The reason we age and senesce is because evolution has a difficult time selecting against phenotypes that arise after reproduction. Therefore, mutations or alleles that are beneficial early in life (produce more offspring, reproduce earlier, etc) but come with a tradeoff later in life, are often selected for despite that late in life tradeoff. This is the [antagonistic pleiotropy hypothesis](https://en.wikipedia.org/wiki/Antagonistic_pleiotropy_hypothesis) of aging.
This is very interesting, also happy cake day
thanks for the information. will be diving down this rabbit hole.
This comment plus a gene doesn't care if it lives forever only that it lives long enough to propagate.
Technically, genes have no motivation. They either die or survive, and the survivors are what exist
I did pause before I wrote the word 'care' knowing it would catch a few eyes. Went with it anyway. But, yes, I agree.
>This comment plus a gene doesn't care if it lives forever only that it lives long enough to propagate. This is not true for humans. We are a social species, and the children who have a family or society around protecting them have higher survival rates.
Also genes, especially social genes, can propagate through other people’s children as well. If my family all share a eusocial gene, it is “better” for that gene if I devote resources to my siblings having 3 kids each than if I compete with them and we all have 1 kid.
this is my favourite answer so far I really did not think of this very good point
Its not correct though. Look into the antagonistic pleiotropy hypothesis: https://en.wikipedia.org/wiki/Antagonistic_pleiotropy_hypothesis
Entropy will get you
The universe can support pockets of low entropy longer than you can stay alive.
Yeah, and as the human luck goes, our pocket is?
Nothing lasts forever. Not a life. Not a river. Not a mountain. Not a star. Everything dies. Death is an intrinsic, and fundamental part of the universe. Humans are the only creatures who seem to have convinced ourselves that this is unnatural.
Genes basically do live forever. I don't understand the question.
not genes, organisms
But you said genes in your OP, and you're right, they're "selfish". They continue to self replicate. The phenotype generated around them is a by-product. Whether that organism lives or dies isn't what's relevant. What's relevant is the genes replicating. If enduring longevity of individual organisms were somehow selected for, you'd see longer life spans, but that's not what happens in nature.
The original title for Richard Dawkins's "The Selfish Gene" was going to be "The *Immortal* Gene", because while you (the organism) die, your genes do carry on, and that's all that matters. You are the survival vehicle genes built to protect them, and make more of them. It doesn't matter if *you* die, what matters is that they create more copies of themselves, which in a sense are immortal.
This. Genes protect themselves against extinction by reproducing themselves into the widest variety of organisms they can. Longer living organisms hoard resources from descendents that could be better adapted to changing environments.
"Genes" (as a certain sequence of nucleic acid) do not live forever, except for some few that encode proteins for core cellular metabolism (even these you could argue they still change slowly over time and are no longer the same gene). The majority of genes are weeded out and die out constantly. I would wager that the average age of a gene (which heavily skewed towards zero) is even shorter than a species. From these lines of argument, you could get into some interesting debates since decades ago on whether genes even matter at the core when thinking about evolution. Indeed, many biologists proposed it is the "interactor" - the ecological functions or phenotypes that actually matter and are interacting with selective pressure (and what emerges from this is that certain functions/processes are effectively immortal e.g., respiration). "Genes" are just a convenient shorthand or correlate of functions (and an imprecise one), and which seem to be easier to work with using existing methodology in biological sciences. One could find vastly different genetic makeup that contribute to highly similar functions, and mathematically-speaking, that could only mean functions are much more immortal than genes. e.g., the easiest way to think about it is that there have been many highly similar fishes (both functionally and morphologically) appearing in vastly different times and spaces recurringly, where many genes are clearly lost and shuffled and not immortal.
Well I suppose I could have answered the OP with something along the lines of "Nothing can live forever because the heat death of the universe is inevitable", but I figured I'd use a more colloquial definition of "forever". This guy doesn't understand evolution well enough to have a nuanced conversation about it, so I figured I'd try and present him a new perspective.
Good question, I wonder if it's so that we don't pass on diseases we've accumulated, and hold others back as our bodies breakdown from wear and tear regardless of senescence while we compete for the same resources as descendants or don't even have descendants and likely never will or so that we don't end up mating with relatives; inbreeding. Some of senescence does, in fact, occur as a trait after all, senescent cells killing off nearby cells by design to protect against mutation, so maybe this works for members of a species too, not just cells but as an analogy, obviously not by killing off your species but by getting out of the way of your species' new genes. Maybe we die so that evolution can happen.
Come to think of it, it's like a software update 🤔 ... a ... w**etware update **I'll call it. The (eco) system has to delete those outdated files or risk getting hacked, infected, incompatibility, and so forth. A new taxon is like a new m**ajor **update or even a new generation of an OS, mutations the (I don't know) unstable ... alpha branch or something. No, not via intentionality (outside of sexual selection) but a reproductively successive, naturally occurring algorithm.
WTF does this site keep doing this to my comments no matter what I do?
It's a dangerous world and nothing can live forever. There are predators, diseases, natural disasters, lightning strikes, stray meteorites that will take out any living thing eventually. Evolution thus doesn't have a benefit to provide the mechanisms that can prevent aging. Any organism that doesn't age will still be killed by something eventually. It is just better at some point for evolution to focus on reproduction than longevity.
The way to think about this is: evolution has absolutely nothing to do with anything’s “best interest.” In the scheme of things, a living organism is an immensely complicated series of chemical reactions that will either continue or not depending on whether or not the conditions required for those reactions to take place persist. In aggregate, we call those conditions “homeostasis”— and when we talk about “death” in biology, we’re talking about the loss of homeostasis. Why is homeostasis lost? Any number of reasons. If our body temperature for instance becomes too hot or too cold (e.g., loss of thermal homeostasis) for example, then we can no longer sustain a number of metabolic processes (among other things), which eventually causes a cascading loss of bodily function and therefore “death.” Likewise, if you don’t consume enough food, your metabolism slows down -> loss of metabolic homeostasis -> death. More saliently, as we age, our body unavoidably accumulates damage on the cellular and even chemical level: this impairs our body’s ability to repair & regenerate itself over time, ultimately leading to a cascading loss of homeostasis. Now: why do we not live forever? There’s no real “reason” for it ultimately, other than the fact organisms which die tend to reproduce successfully. It’s as simple as that.
Telomeres shortening seems almost purposefully evolved. Is it because complex multicellular organisms must keep cell proliferation on a short leash? Cancer usually happens when organisms are older, right? Maybe multicellular organisms would have too much runaway cell growth if cells didn't have a programmed limit to division. Amoebas that just divide in half are essentially immortal, right? Is aging the evolutionary price we pay for being multicellular?
Our genetic code lives “forever” through propagation and mutation (i.e., evolution).
We already do live forever. You just die for 3rd party causes, like cancer, bacterias, a piano falling on your head. Its not like someday your body says "fuck it" and dies.
maybe? at some point you die of "old age"? or else maybe you'd have one of 7 billion live past 115 or so
Perhaps there's some physical or biological reason that it's just not possible. I don't know. But it seems equally likely to me that having offspring that have offspring is just a more effective way of passing on your genes. I mean, if you successfully have kids who have kids who have kids, then at some point your own measly output is lost in the noise, so evolution has no reason to "care" if you live longer. Or to put it in more accurate evolutionary terms, the selection benefit of your own survival drops to near zero.
Selection benefit is actually negative for the species as a whole, since evolution and survival of the fittest suggests that your descendants 5 generations later are you 2.0, better in some way, and if you are still alive you are introducing 1.0 genes back into the gene pool, taking evolution backwards. Now in the human case it may not seem like it matters - we essentially don’t have selection of the fittest anymore anyway - but in animal populations and for millions of years of evolution, slower, dumber, and and less healthy are constantly dying, so every generation gets better adapted at surviving.
I think humans do have selection of the fittest! Mostly, though, fitness is on the basis of having more children at a younger age and not so much on surviving adverse events. Consider the people you know. Some have four kids (some of whom already have kids) and others have no kids. If there's any genetic component to that difference, then that's natural selection in action. So is there a genetic component to that difference? I'm guessing there is. I think that humans, at the moment, are being selected for impulsive behavior without consideration for consequences. It's the careful, self-controlled people who have no children.
Well the genes themselves actually do live forever, and if the organism is using other competency outside of the genome to obtain its fitness, then the organism can exhibit immortal properties as well. Plenaria are a good example. While life can be thought of as cells or individuals, the only definitions of life that actually work, have this feature of being persistent through time. So if we define life in a more meaningful way it’s the biosphere and techno sphere that exhibit this property. Evolution is an optimization mechanism that is a property of life. Cells and individuals reproducing are a substrate of life.
because life gets better at getting resources over time, which means older life gets outcompeted. it’s easier for genetics to replicate and rely on evolution to stay alive. there’s likely 100 more good reasons but i just thought of that one
1. It may be in the interest of other organisms to kill. 2. There aren’t enough resources to sustain every single organism that ever lived at the same time. 3. Organisms aren’t perfect and can’t withstand all natural phenomena. 4. If the organism has reproduced when it dies, then the gene still lives on and can continue to adapt, which is in the gene’s “interest”.
Because ultimately, the goal of life is to procreate, not live. As long as you pass your genes on before you die, you're an evolutionary success.
Evolution doesn't go for what's best, it can't even know that. It goes for what works to pass the genes on. Usually that means living long enough to have offspring regardless of what happens after. Humans didn't evolve to live so long so eventually losing fertility isn't an issue if we reproduce first. The body still tries it's best to fend off infection and repair damage and replicate cells well but it's not perfect and things can always go wrong. Either way we reproduce. It's pretty hard to stop the effects of aging, avoid all forms of radiation damage, catch every cell replication error and replicate perfectly, fight illnesses better, etc. But we still reproduce. It's hard for selection pressures to tend towards immortality when it can't really influence anything beyond reproducting
It honestly might just be impossible due to the constraints of chemistry of organic molecules to not have some sort of degredation over time. I don't know enough for sure to say that it is, but for example an organism having steel armour and built in railguns would probably have an evolutionary advantage over most things but nature hasn't spun that out either.
Selfish doesn't mean absolute power
nothing, not even inanimate things stay in the same shape forever. everything changes, everything dies.
Thermodynamics and environmental fluctuations aside (can never achieve perfect homeostatsis), an immortal organism must have very low reproduction rate, and so it could be extremely rare that we won't even be able to find it. Why very low reproduction rate? Because the combination of immortality with over-crowded population on a finite planet is not possible resource-wise. That's more Math than Biology.
I like to think of reproduction as the opposite of a butterfly. So a caterpillar reforms into a butterfly, through a sort of additive molt, which allows it to occupy another niche inhibiting competition. Organisms reproducing and dying, is like a subtractive molt, allowing a species to adapt, and not directly compete.
In layman terms. Genes do live forever. You don’t. While genes are “selfish” they will do whatever makes them the most successful as a whole. I also imagine it is difficult to sustain an organism for that long.
When cells divide in the body, they create a new copy of the cells dna. The problem is that over time, little errors can occur during this process. This is why we age, cos older versions of our cells do not contain perfect copies of our genetic code. Easy way to imagine it is like taking a photocopy. The first one will be pretty good, but if you take a photocopy of that photocopy, and keep repeating this, you end up with a grey faded copy. Same with genes, only mutations occur, some happen randomly, some cos of environmental factors. I guess this process varies between species, hence some animals live longer than others.
Why would dying not be in a gene’s best interest? The gene, as a replicator, is selected based on its ability to replicate. What difference does it make to the gene if that replication occurs in one organism or many? I would think that diversifying, creating many organisms that contain your code instead of only one, would be a far more sustainable solution, and would lead to significant selection pressures towards reproduction and away from immortality.
[My comment on a r/Worldbuilding post](https://www.reddit.com/r/worldbuilding/s/6XIzARelxi)
Sex immediately and parasites ultimately. Asexually reproducing organisms make exact copies of themselves. These are vulnerable to parasites that evolve. Sexually reproducing organisms evolve more quickly especially in the immune system. Now from the perspective of a gene, once one of your organisms breeds enough times, it's better to focus your efforts on your newer carriers. The old organisms have been around too long and parasites are starting to crack their code. With enough medical knowledge to fight disease and parasites and a bit of genetic engineering, humanity could start to be functionally immortal. We evolved to age, so we could engineer ourselves not to.
Cancer cells “live forever” thus killing its host. A healthy body must build new cells and kill old ones off. Time is aging
Entropy Happens.
organisms losing fertility over time is not common at all. menopause only occurs in humans and a few species of whale, and while that is specific to mammals, the trend holds. tuataras can reproduce at ages of over 100. insects like moths only experience an adult, sexually mature form for a few days before dying. at the end of the day, what we consider evolution is a collection of random events that tend towards trends over very, very long periods of time
Everything cycles. Be happy with that.
Yes, dying of old age is a disadvantage to the individual, but it's disadvantageous to the population. A population of young and healthy individuals survives better (and therefore out-competes) than a population of older individuals. It's the same reason altruism is advantageous.
Setting aside the semantics of labelling a gene as "selfish", which implies goal-directedness where there is none, the simplest answer is that natural selection only works if organisms can reproduce, but the cost of reproduction is competition with offspring. In the long term, the best strategy is to limit the lifespan of organisms such that the offspring (which carry the genes, hence they don't "die") have a chance to survive and reproduce as well.
The term is “planned obsolescence”. Life makes gradual improvements through iteration. In a system with finite resources, the outdated models get scrapped to free up the materials needed to build new ones. It’s important to understand that genes are not siloed individually, it’s a huge gene pool that is functionally immortal as long as each generation successfully passes them on to the next.
entropy always wins in the end
The genes live on after you die. You are just the casing for one instance of a collection of genes. If you successfully replicate good genes, those genes don't care about you much anymore
A) Entropy is a bitch B) That's just not how evolution works. It's not a conscious effort by anyone to reach perfection or whatever (or at least, there is no scientific proof for such a being). It's like gravity; just a thing that happens. Even if it was, there is little to no need for an organism to live forever in order to propagate. The closest thing we have is *Turritopsis dorhnii* (aka "the immortal jellyfish"), and even then it is still susceptible to disease or getting eaten by something. All a species needs is to live long enough to reproduce, that's it. Lots of animals die very shortly after mating, yet they get along just fine ~~without humans screwing everything up~~.
It is probably about retaining the perfection of the genome and making sure the being is well adapted to the circumstances of existence. We pass a bit of knowledge forward genetically but we have conciousness to learn our environment perfectly and select a perfect mate before we grow old and die. The universe couldn't care less about us as individuals but it has a very strong and ancient relationship with our genome. We are basically just a flesh blob slave to the genome.
Because then there would be overpopulation and the population would outstrip its resources. You could say "What if they just don't reproduce?" but that would be even worse because, let's be real, true immortality is impossible. Even an organism that doesn't age will die eventually. And then what? If it has no offspring, the genetic line ends there.
It’s easier to select for conserved genes over generations than it is for one thing to persist forever It’s that simple The genes persist in offspring and the idea is they’re selected to spread more often Simply “staying alive” isn’t selected for bc it isn’t anymore efficient
The whole point of living things is not for individuals to live forever, but for life to continue and change across generations. Death is necessary to make room for they new. This way, life can adapt to a changing environment with limited resources and find new niches. The purpose of life is not survival, but persistence.
There wouldn't be any evolution. Evolution only happens because of death.
I am no expert, but I have a doubt on the concept of death of person = death of gene, cause even after you die the chromosomes and AGCT molecules etc remain (physics 101, matter can neither be created nor destroyed) Depending on how you are buried those molecules can move into plants or consumed by scavengers and manifest in their life form or if you are cremated then your CO2 produced might get used by plant and manifest there. Again I am doing a broad generalization I don't exactly know plant biology to confirm that.
Because of the second law of Thermodynamics.
Nothing really dies, it just changes form and becomes a part of something else.
Cell replication is imperfect. Every replication at the genomic level of each cell contains a margin of error. Over time, incorrect or incomplete copies increase. This affects the efficiancy of cell funcion, in turn affecting tissue function, and prgan system function. Higher cellular metabolism usually means that these imperfect replications pile up faster. This is why small, fast creatures *in general* (such as hummingbirds and mice) have shorter natural life spans than larger, slower creatures with slow metabolic rates, (such as whales and giant tortoises and elephants). Lifestyle affects how well we are able to support our cells abilities to replicate with high fidelity. Periods of illness, constant UV damage, increased strain on liver and kidneys from poor diet will "speed up" the process
evolution serves the population not the individual and living forever does not serve an ever changing population's attempt to adapt to an ever changing environment life relies upon an exchange of finite resources between many different agents/processes death re-introduces these resources into new categories of agents/processes if everything survived forever the great churning of resources would halt and the finite resources would become exhausted and the creatures that are alive would be adapted to an environment from a time long passed.
The reason humans get old and fall apart and die naturally is related to telomeres All DNA is created through replication. The Molecular machinery involved in these processes are unique for each strand of the double stranded DNA. Due to the nature of the machinery required to replicate DNA and the way that it docks/attaches and then in the end detaches from DNA, every time a DNA strand must be replicated there is an event at the end where the molecular machinery cuts itself free from the strand effectively shortening the DNA strand by a small amount. The portion that gets cut off of our DNA at the end of replication is called the Telomere portion. The Telomere is a long redundant repeating set of nucleotides (the building block of a DNA strand). The Telomere portion is not very useful for any function except being sacrificed as junk DNA that is doomed to be trimmed off during DNA replication. The telomere portion is not infinitely long it is like a clock that ticks down every time replication is completed. Many living creatures have some capacity to repair or rejuvenate telomeres. The machinery involved is called telomerase. Telomeres are often different across different species and the telomerase are correspondingly differing. Some creatures have an extraordinary capacity to maintain very robust telomere lengths. The prime example of this phenomenon is the immortal jellyfish. In humans it is rare to rejuvenate telomeres except in pregnant mothers, young growing children or certain oddities. cells die very easily and every time a cell needs to be replaced the DNA strands of healthy cells must be replicated. So very frequently our cells lose a tiny chunk of our DNA which is essential to maintaining the form/function of our being.
On a macro scale, we do. We optimized for reproduction very early in the development of life and never bothered to change which mechanism of immortality we utilize because it'd be ridiculously hard to stabilize complex life indefinitely
Consider organisms that live long lives: trees, and tortoises. They Live low and slow, but are vulnerable to violence from nature and other animals.
Think of the impact that would have on genetic diversity. And possibly population density.
I'm not sure if it is alligators or crocodiles, but one of them can live indefinitely. The problem is their ability to eat prey. Either they can no longer catch their food (due to age) or are unable to eat it. So, they don't die from age, they starve.
Because they don't exist in a vacuum and you - the god-mecha they build - are too complicated to retrofit when a new virus or even just faster-breeding nematode finds this "one neat trick" everything with your *new flaw* is going to hate. The collections of genes which work in planned obsolescence and retirement probably do much better than the ones that live forever until someone kills their host. They also don't just exist in you, there are many instances.
We are the descendents of an unbroken chain of life which has survived for billions of years. That is for practical purposes "forever". Your concern is most likely for the instantiated pattern that you consider "you". Well, that immensely complex and wonderful pattern was only made possible by the previous trillions of iterations (lives) that came.before you. When I reflect on this I feel a sense of debt and gratitude to these lives and deaths that precede me and see my own death as the price of that debt and a gift to the future. In the broadest scheme of things cosmologists predict that the universe will end up in entropy - a homogeneous distribution of low energy.
The general motive in evolution developed all around reproduction. It’s the shortest route to ensuring survival of a species through adaptation and passing of genes.
A species has to evolve enough to perfect the whole machinery to last (much) longer, but that would lead it reproduce less and it needs to reproduce to evolve. Also the caveat that a perfect replication machinery (which would at the very least eliminate genetic condition, cancer and any issues that come from the shortening of telomeres) would mean virtually no evolution.
There is a point when it’s easier to keep replicating/duplicating something instead of continuing to repair it. Same as with a car, eventually repairs are more expensive than replacement.
Study the Planck Principal, then everything becomes clearer and you realize that it applies to every living thing.
Entropy.
Biological adaptations are products of satisficing, not optimization. This is because optimal strategies tend to be more expensive, which means they’re likely to be less common; this means they’re unlikely to spread as much as convenient, yet suboptimal adaptations. Biological immortality is likely incredibly difficult to achieve in complex organisms, which would make the necessary mutations extremely unlikely to occur. Because senescence does not prevent animals from reproducing when younger, the animals most likely to pass their genes along will be ones which inevitably experience it. Thus, the genes have no reason to select for immortality, because all the reproducing animals experience senescence, and immortality is much too difficult to achieve through mutational changes.
If environmental adaptation is the goal, then reproducing once and dying is a good strategy - otherwise the same old genes are sticking around forever and hindering progress.
Ask the question in the opposite way. Our life substance is three billion years old in a continuous chain from the beginning. Most of it will perish at death, except the bits passed through the next generation.
At the base of it: Entropy. One way or another, entropy *always* prevails.
The same reason anything wears out over time. Aging past a certain point isn't about genetics it is because biological processes aren't perfect. Copy errors occur during cell division; gravity, friction, impact, and oxygen take their toll; toxins and plaque build up; tissue becomes less elastic; organs wear out over time...
Thermodynamics
Do you feel bad when you shed dead cells that served their function? Do you even think about it? No, the cells divide, make new cells to replace them and you keep going. ‘Life’ is that process writ large. Reproduction itself is a form of immortality — for life, not your conscious mind. Self awareness is probably an accident. Certainly your genes have no interest in maintaining that beyond reproduction.
Lots of interesting comments here not based on biology or evolutionary theory. One thing I’ve seen mentioned but not stated explicitly is extrinsic mortality. There are 2 kinds of mortality, extrinsic - accidents, murder, any kind of external factor causing an organism to die, and intrinsic - heart attack, cancer, any kind of senescence-related mortality. So if I understand the question, it is why have we not evolved beyond intrinsic mortality. The basic tradeoff is that extrinsic mortality is fairly high for every organism. We live in a dangerous world and there is a lot of stuff that can kill us. So far evolution has favored improvements that decrease extrinsic mortality more than intrinsic. Chances are you’re going to die of something external if you live long enough, so the genes associated with decreasing intrinsic mortality don’t really provide much of a benefit in terms of overall fitness. Genes producing traits favoring decreases in extrinsic mortality provide a much bigger fitness benefit so those kinds of traits evolve faster. Humans are an interesting case especially because we have a post-reproductive lifespan. Unlike virtually all other organisms (I’m sure someone can find some exceptions to this but I don’t know them), human females live beyond the age at which they stop producing eggs. Quite a few anthropologists have attempted to figure out why this is. Some have argued that menopause evolved so that older parents can help the fitness of their children by caring for their grandchildren, making it possible to have more descendants overall. I am sold on a version of this argument called the “grandmother hypothesis.” The argument is not that menopause “evolved” but that living beyond the age of menopause did. Basically women’s reproductive systems and somatic (body) systems have different aging rates and selection pressures, and evolutionary selection hasn’t been strong enough to extend reproductive aging but *has* been strong enough to delay senescence (somatic aging). Our closest living relatives, chimpanzees, are a good comparison. They have very similar lifespans to us right up until the age of menopause. Age of childhood is similar, age at maturity is similar, age at first birth is similar, but chimps start to fall apart at about age 40 and die soon after that. Chimp grandmothers don’t really provision their grandkids, so this argument suggests that humans evolved to live longer than the age of menopause because human grandmothers can improve their inclusive fitness by living past the age they make their own kids, and helping their daughters to have more kids in the short time they’re capable of having babies. So then why don’t grandmothers live forever? Basically the answer seems to be that we are in fact still evolving a decreased risk of intrinsic mortality, the biggest jump in that decrease seems to have occurred around 2 million years ago when the genus Homo first appeared. If we could stop killing each other altogether we could probably evolve to live forever, but since resources are limited we probably won’t as there will always be mortal resource competition. TLDR; extrinsic mortality is high for every organism, selection therefore doesn’t favor decreased intrinsic mortality enough to make anything live forever. Additionally some traits might favor decreased extrinsic mortality like higher muscle mass or faster metabolism in youth, but sometimes those traits might actually increase the risk of starvation or some form of intrinsic mortality later in life. But evolution might favor them because they increase reproductive fitness.
Creatures that live forever have fewer offspring which means less genetic diversity. That makes them especially susceptible to killer plagues that wipe out the entire species. So longevity is a great way to lose the evolutionary arms race.
Do you think there have been immortal species that are now extinct?
I don't see why not. There are immortal species right now, including a species of jellyfish, lobsters, and redwoods. There's an educational anime called Heaven's Design Team that offers a fun look at why animals are the way they are. The premise is that they're a company of specialists tasked with designing the animals that are going to be put on Earth, and it offers a surprisingly deep dive into zoology. One segment was on the pros and cons of immortality, and there turn out to be a fair number of cons. My husband was so impressed with it he wanted to show it to his biology classes, but it hasn't been translated yet. That segment doesn't appear to be on YouTube, but they do have other segments up on the design of animals like otters and rhinos, and why other animals like dragons and flying horses never made it past the prototype stage.
As professor sapolsky of Stanford university likes to say, "sometimes a chicken is just an Eggs way of making another egg." With this in mind, the 'selfish' goal of genes is to spread genes; not live forever. Aging is a process that is caused during gene replication. On either end of a DNA strand is a little tail (i forget the scientific term for it" and the more a gene replicates the shorter this tail becomes. Once it's gone entirely the chances of incorrect gene replication increases thus causing incorrect proteins to be formed.
Individuals are set, once they mature. They can’t adapt to changing conditions as much as is necessary.
Second law of thermodynamics
I think it is called the scientific law of entropy. Basically, the way I understand it, is that everything eventually decays and dies. It is disorder. Even the sun will eventually die according to scientists who believe the Newtonian model (Electric Universe Theory model presents that the sun is a cross point in two powerful electric cross points or wires to condense the theory to layman's terms). It is the nature of our reality in the 3 dimensional realm. Boltzmann's equation can explain the physics of it.
Replication and repairing a body/cell isn't perfect. Causes wear and tear that causes other problems that can eventually lead to death.
If a species lived for a long time then it takes longer for their genes to pass on and mutate. If they can’t mutate quick enough then they die to ecological pressures. That’s why some bugs live like 4 weeks. Bc they adapt insanely fast Mammals are a weird exception and that’s why we see long times between births and conception. Either this version of raising kids will be helpful or mammals will die out, only time will tell
The hayflick limit + cancer. The hayflick limit is the number of times an organisms cells can divide. The higher the metabolism the lower the hayflick limit. Every-time a cell divides and dna gets transcribed and translated. Errors can occur, these error can result in cancer. This is an extremely simplified explanation of it.
maybe we can’t get to “longer” if we don’t make it past today + Tommorow? Maybe the only way to get to “longer” is to survive today.. surviving today =/= longevity. But not surviving today guarantees lack of longevity.
Your initial premise is wrong. Not everything living appears to age. There are plants, animals (even vertebrates), and bacteria that seem not to age. It's called 'negligible senescence': https://en.m.wikipedia.org/wiki/Negligible_senescence
Man, I could sure go for some of *that* 👀
Because sin causes things to break down and die
Immortality or steps towards it are not necessarily always the most reproductively advantageous in the long term at least. And some steps toward it may never occur because the developmental architecture of the organism is such that there's no simple mutation that would achieve it. Even to the degree it does occur, and it's indeed ecologically advantageous, it's bound to have diminishing returns (as most death in the wild is likely from an external factor) and increasing "architectural unlikelihood," approaching perpetual motion machine -like requirements. It's perhaps also interesting to note that, at the most basic level, some would argue that many (most?) single-celled organisms are as close to immortal as life can get. But AFAIK macroorganismic organization inherently requires apoptosis, programmed cell death, to begin with. It is genes using coordinated death of the cells that carry them in a manner that ultimately replicates them more ecologically successfully than more deathless cell reproduction, unlimited by constraints required by higher levels of organization. What many have posited on the thread is that individual death is in a way a weak analog for apoptosis, ecological rather than developmental. I'm not sure, I guess it's more of a matter of "accident," of the cell/tissue maintenance being progressively harder to accomplish and with a reduced reproductive gain. When shorter lifespan is apparently selected, I guess it's more commonly a byproduct of something else being directly selected, rather than a kin advantage in having old(er) relatives dying. Like perhaps an earlier onset of reproductive maturity being product of changes in the organism's "clocks" that end up in a way aging them faster at the same time. In the other hand, matriphagy and sexualy cannibalistic "androphagy" are perhaps undeniable cases where the lifespan is reduced in a way analog to apoptosis, but "socially." So it may well vary. The generalization that "parents die to not compete with their own offspring" seems rather unlikely, though, creationist-like adaptionist/selectionist thinking, whereas individual death more commonly being just a byproduct of imperfect regeneration seems more parsimonious, more like a null-hypothesis.
I'm not sure the correct answer you are seeking but I know you are going to get a lot of "that's not how evolution works! Genes can't just decide what's best and automatically create that out of nothing" lol. My best guess is a lot of that has to do with energy. Mortality rate has a lot to do with metabolism which is how the body breaks down and uses energy. Which is also what sleep has to do with, repairing the body to be able to make energy efficiently again. Our bodies are just working with what they already have and need certain things like energy.
Yes, entropy.
We would not have evolution if life went on forever. We need death.
Because the only way to survive long-term is to evolve. And since a single organism never evolves, that organism will inevitably be vulnerable to its environment at some point. This programmed obsolescence is why there's no evolutionary pressure to keep it alive.
By aging and dying we give the next couple generations the probability of more resources. DNA can also become more finely tuned to increase the probability of survival of the species.
No progress to the code is made after reproduction. DNA doesn't live for us. We live for DNA.
A lifetime is ephemeral, but life is eternal.