I’m not an evolutionary biologist, but I think that the longer an organism’s lifespan is, the slower the rate of reproduction and therefore there will be a slower rate at which the population is capable of evolving. This will put the population at a disadvantage compared to a faster rate of evolving in the event there is environmental pressure.

I think of this as a curve fitting problem: finer granularity of the data points (a shorter lifespan with faster sexual maturation) would more quickly produce a wider variety of genotypes, some of which are more suited to fit to a rapidly changing environment (the curve). On the contrary, rougher granularity of the data (longer lifespan, slower sexual maturation; instead of data points, data line segments trying to fit to the curve) would be more suited to a flatter or gradually shifting curve (a more slowly changing environment).

I think if you have an acute environmental shock, as is happening right now with global warming, the folks who have lots of kids at a younger age will have the genetic advantage from a population perspective (ignoring influences from financial and technological resources).

Repair mechanisms cost energy even when they're not being used. Immortality requires much better repair mechanisms, that makes the owner less competitive. Thus the immortal loses the evolutionary race against the mortal.

In practice immortality in a complex organism requires many steps, those will never be done because they up the energy budget and put the creature at a disadvantage.

The fact that it's an evolutionary disadvantage not to be replaced with superior offspring is irrelevant, that implies intent which evolution does not have.

?? It does not imply intent. Pretty much by definition an evolutionary disadvantage is something that nature will select against. You appear to have forgotten that not only does individual compete with individual, but also population with population.

FWIW I'm a biologist, though I've only done a little bit of work on aging.

> For example, if there was a human or animal genetic pattern that made the organism not age, wouldn't that organism have created many offspring (in its long life) and the mutation have spread?

First, aging is extremely complex and caused by a host of factors. No single gene or regulatory sequence could cause or prevent all of those things. Take DNA damage, for example. Read through this wikipedia article and notice how just within this single issue how many things can go wrong: https://en.wikipedia.org/wiki/DNA_damage_theory_of_aging

> Does the fact that we don't (appear to) observe any ageless vertebrates or humans mean that it's probably not a genetic problem?

The right way to think of this is that there's no genetic solution, or that one hasn't evolved yet in humans.

> is life on Earth already so old that everything that will exist has likely already evolved?

Evolution isn't linear. It just optimizes for whatever the current situation is. New genes are still being created (on evolutionary timescales anyway).

Until very recently, the average lifespan for a human was in the 20-30 year range. Even if lifespan-enhancing genetic changes did occur in some individuals, those people were dying of bacterial infections or starvation or whatever, so they never got the chance to live 300 years and have 280 children and thus "take over" the population. Also, as others have pointed out, genes that confer longevity may come at a cost. Humans are just so complex that every change is a tradeoff.

My guess would be because it is all about balance: If organisms live too long, their species has it harder to adapt to changing circumstances, and overpopulation/resource availability cannot be as finely tuned as with shorter life spans.

Perhaps those who lived shorter had more energy and drive in their youth. This might be biological, but this could also be some kind of mid life crisis. As opposed to someone who knows they could live to 300 years and be complacent. Perhaps the long lived complacent ones were taken as slaves or lost in battles.

> "Alternately...is it possible that there are adaptive genetic traits that have not yet evolved, but will evolve in future, or is life on Earth already so old that everything that will exist has likely already evolved?"

Evolution seems to be a really ineffective mechanism though. It's sort of like how planets "evolve" to support life. Most don't. Some planets might need a terraforming lifeform to evolve. Evolution has done its duty, but now it's up to us mortals to take the next step and evolve ourselves.

You can argue that life saving medical techniques make us more likely to select for cancer and the like, but it doesn't really matter as long as we can eliminate it.

I don't think so. Evolution only "cares" about reproduction. Once you reproduce, you're sort of done from an evolution perspective. So, there is no evolutionary pressure towards immortality because mortals multiply just fine.

what if you are the 30th child?

Human babies are pretty helpless. Children need their parents until about age 10, to have a good chance of surviving to adulthood. So humans need to be around for many years after they reproduce, in order to contribute to the gene pool.

Yes, and grandparents can have the ability to contribute a lot to the success of their grandchildren. In contemporary times, a wealthy grandparent can send many grandchildren to college with their wealth. In the past, it could’ve been other resources as well as the preservation of knowledge and culture.

To this day, the presence of grandparents in a child's life contributes to their success. If nothing else, the "free daycare" frees up the parents to continue their careers; but also child-rearing is a skill (more like, a billion skills) that don't get passed on unless folks survive through their grandkids' adolescence

Sure, but living 500 years vs 20 years post-child birth confers no additional advantage to raising the child, so again there is no pressure selecting for this kind of trait.

A fine tuned short life and then death after reproduction cam evolve, as we see in numerous octopi, who are very smart as well as very prolific and are programmed to die after reproduction (in almost all cases)

There are, in fact, some (very primitive) organisms which don't appear to age. They're just not very complex, or large. Which is probably not a coincidence, and suggests that ageing is not (in humans and other complex species, anyway) only normal entropy, but rather an adaptation.

Telomeres, for example, put an upper limit on how many times a cell can divide; much of the anti-aging work is focused on getting around this limit. But, telomeres are an important anti-cancer adaptation. The fact that they limit how many times a cell can divide, and thus how long the cell line can persist, is not a bug, it's a feature, and in fact the primary feature. If you managed to disable them, you would not become immortal, you would probably die sooner (of cancer) than you would otherwise.

It's also not uncommonly the case that changes in society come from the younger generations, who get power as the older ones die off. If Stalin's generation had lived forever, the Soviet Union might still be shooting people who tried to leave. Actually that wouldn't have happened because we would probably still be living under the god-emperors of the ancient empires.

But, a society next door that did NOT have agelessness, which was therefore more able to innovate, would eventually come across the border and kill off the ageless.

This is a good premise for a movie!

Only if it stars Sean Connery in a red diaper.

I'd like to give an answer from system theory ranther than biology: In order to create a system that works infinitely every single consumption must be met with an EQUAL production. If there is any imbalance it will add up and block a subsystem at some point in the future which will domino its way throughout until total failure.Think of a 1 byte production(memory leak), or a 1 transitor consumption(physical failure) over infinite time. Biology has a very throw things together and iterate what sticks style which is somewhat contrary to the fine craftsmanship required for perfect balance. For all we know, biology might have already taken a design decision which will never be able to be perfectly balanced out, or perhaps we're 3 steps away from engineering a fix.

Good question. Agelessness is not as sustainable as reproduction. If something lived "forever" the ability to reproduce would have to go down to prevent overpopulation. The race would then be more wounerable to disease/disasters where a large population would die.

I guess the fact that the lack of mutation in a single lineage increases overspecialization which could lead to death en mass, is important too. So short, promiscuous lives maximize random changes in the gene pool, which increases the species' genetic diversity. That's the most convincing argument for me right now. If only there was a shot to make you not age, but also to mutate your germ cells to simulate greater diversity...

Of the ways for a species to go extinct few of them have to do with aging. So on an individual level, yes it would be a strong selector, but on a species level, it could be neutral or negative.

So agelessness isn’t a 100% win by any means.

We definitely have not seen every combination of possible genetic traits yet. To my knowledge the griffin has not yet evolved, for example.

Optimization of the gene pool happens only during the process of reproduction, so everything else gets ignored. Evolution doesn't care about your wellbeing or morality. Male mantis gets eaten by female mantis after reproducing. There are cases of animals killed by their own overgrown horns. Nature doesn't care about anything that happens after reproduction. It doesn't even care about your wellbeing before you reproduce as long as you reproduce. Evolution doesn't have an end goal - it just happens. If you want to go down the rabbit hole then look for efilism - life spelled backward.

Jellyfish and the secret of immortality

https://www.nytimes.com/2012/12/02/magazine/can-a-jellyfish-...

[..] We now know, for instance, that the rejuvenation of Turritopsis dohrnii and some other members of the genus is caused by environmental stress or physical assault. We know that, during rejuvenation, it undergoes cellular transdifferentiation, an unusual process by which one type of cell is converted into another — a skin cell into a nerve cell, for instance. (The same process occurs in human stem cells.) [..]

Humans are evolved and we will at some point increase our lifespans even more, perhaps to the point of immortality. It may be the case that a conscious mind like a human mind is a hard prerequisite to then leveraging tools to build technology that makes us immortal. In such a case I wouldn't expect regular animals to be capable of achieving this through sheer brute force over billions of years. Might need to flatten all those additional years of evolution into CPU-time and let an AI figure out how to do it for us.

Some deep sea octopus species can regenerate into younger stages of their lifecycle, rendering them effectively immortal. Excerpt when something eats you, which happens a lot in nature.

It hasn't been selected for in humans, but that doesn't mean it's a genetic problem. There are however ageless vertebrates including turtles and salamanders.

Also there was a 507 year old clam discovered off the coast of Iceland. https://www.sciencedirect.com/science/article/abs/pii/S00310...

I can't articulate it very well, but "The Red Queen" [0] offers a theory whereby sexual selection evolved as a defense against bacteria, viruses. It seems as though it may be disadvantageous to live too long as these mechanisms wouldn't be refreshed.

[0]: https://en.wikipedia.org/wiki/The_Red_Queen:_Sex_and_the_Evo...

A more interesting question might be: what is the evolutionary pressure that caused convergence towards aging across essentially all multicellular living things on earth?

Aging (decay) is not evolved, it's the default that needs to be fought.

The thing is, we don't know really. Is aging evolved, or a disease? Or a complex of some evolved and some diseased mechanisms interacting... Or something else.. i don't think we know yet for sure.

We know, you can see it under a microscope. Take the simplest living structure, you'll see it will break down over time. Then go progressively bigger - you'll see the organism is doing work to keep itself together and well. These mechanisms are increasingly complex with scale, and not designed with that (or any other) purpose in mind, that makes it extremely convoluted and sometimes even counter-productive. The problem (from our point of view) is that there is no reason to keep doing this work after we procreate, that caused us to evolve workarounds instead of solutions (e.g. telomeres long enough for few decades, but not more).

I definitely want to reply you, I'm just a little occurred right now.

actually I don't think that's what you'll see in a given time. I think if you take the tiniest living organism and look at it under a microscope you won't see it breaking down over time you'll see it reproducing or eating or moving around. I think it does those things with greater frequency and on shorter time scales then it breaks down. And I'm pretty sure there are some tiny organisms that you know don't break down at all.

But I'm not denying that breaking down and entropy is an almost universal fact of life for most of life.

and I agree that from an evolutionary perspective there's no point repairing the body after the sort of population average procreation age. and in fact I think someone else mentioned in this thread that you know there's some organisms that die immediately after procreating. And I'm also not disputing that repair mechanisms and things like telomeres have a genetic origin... that seems obvious.

However this sort of decay behavior and repair behavior is not universal there are some things that are a lot more durable but even if we assume that it's universal, i don't think you can tell or I can tell whether, nor the extent to which, decay is a disease or genetically evolved solution to some problem that we don't understand yet, or some complex interaction of the two.

The possibilities of some of the potential consequences of immortality have been discussed in this thread and people have proposed aging as a genetic solution to that, and an explanation for why agelessness which, on the face of it seems like it would be adaptive, has not evolved. So I honestly don't think we know the degree to which aging or agelessness is genetic or is diseased, or a complex of both. And I don't think your relatively simple, but still on some level convincing, example establishes that either way.

Others here have hit on the main points, and Richard Dawkins has made interesting comments on it in The Extended Phenotype. Here's my distilled answer:

Death due to ageing may be dwarfed by death due to other causes. For example, look at short-lived mammals like rodents: An individual is likely to due of predation before senescence. And, everything has a cost: The (short-term) survival and reproduction cost you pay must be worth it.

The fact that we haven't found ageless vertebrates means that being immortal is maladaptive for a species. This implies that we are genetically programmed to die.

Immortal species may have appeared, but they probably went extinct, because they had to have few offspring to prevent overpopulation. With fewer offspring, there is less genetic variation, and less ability to adapt to environmental shocks, such as new pathogens.

You don't need to even go as far as immortal. Just assume a human lived to 500 years on average.

They would accumulate a lot of damage over that time (muscle tears, concussions, broken bones that don't fuse properly, etc.). This would lead to a lot of people in your tribe needing help doing simple tasks. Which would cost your tribe energy.

Instead reproduction takes some more energy in the beginning (feeding and teaching), but there's a break-even point where the offspring can provide for the next and previous generation more efficiently.

I'm wondering if people would be less stubborn and more flexible if they died later. Otherwise you'd have people asking you to get off their lawn for 430 out of their 500 year lifespan.

Somewhat related paper you may find interesting: Does Aging Stop?

https://pdfs.semanticscholar.org/6dff/ee493ddc2e294f32413186...

Agelessness would only have evolved if it was advantageous to our species. Living far beyond the time it takes to parent offspring is of little benefit, as ancestors are in competition for resources.

Isn’t aging controlled at the cellular level? Mitochondria etc? Routine stem cell therapy thru life may be the best approach.

We live in a time where old age is a big killer but in history the killers would have been war or disease so maybe optimising for longer life wasn’t worth it.

What you describe is very common in this planet, in fact, there are thousands of cases and is called agriculture.

Genetic longevity has evolved.

Consider a queen bee. Her livespan is so much longer (several years) compared to the worker bee (4 weeks during spring/summer/fall, until winters end for the hibernating generation).

The Queen's task in the live of the hive is to provide an unqenchable source of high quality genetic material to grow worker bees from which in turn will provide the hive with the periolous work required to sustain the hive.

And yet still there is an end to the queen's live.

Cloning a plant from a branch by covering a branch in soil, have it grow roots and then sever the connection is a mechanism of getting a new copy of the organsism. It might be interesting to find out if that resets the clock on a multi-year plant in respect to the original individual from which the branch was taken... Consider the top of an pineapple... you can grow an entire pineapple plant including the fruit from it...)

So longevity is not the absence of aging.

There might be serveral distinct constituents to aging:

1 the accumulation of damage (wear and tear)

2 an actual genetic programmed decline of biological function

3 an update to the genetic programming of the entire organism is not feasible

1 There might be damage which can not be repaired. For example there might be toxic substances building up or there might be a limit to the complexity or plasticity of a neural network. After exceeding such a limit the function may no longer be available in the required quality (Cortanas's Rampage..., Prions, the degradation of tendons (for example: the ligaments in a humans knee degrade...)

2 There is a cycle of life which has evolved in multicellular organisms. Single cell Organisms still have a cycle while not aging:

Build up sufficient material in the cell to sustain 2 individuals * divide into 2 individuals, such that every clone has at minimum the required parts to sustain itself * repeat

All multicellular organisms start reproduction from a single cell. In their youth they build up to their adult forms which are reproductive. After reproduction the parent generation may or may not nurture the offspring.

The complex mechanism of growth from a single cell to adult form relies on molecular clocks: Puberty starts at a certain age, and even before that the development of the embryo requires a sequence of aging - for example the fingers of a hand develop out of a flat proto-hand because the cells between the fingers die. So autocytosis - programmed cell death - is essential to the development of an organism.

*3 Evolution works by altering the genetic programming by mutation in the offspring, putting these copies in living specimens of the next generation into the environment and just by chance the mutations prevail whose specimens did not die before reproduction.

So longevity and aging is of no concern to evolution by itself.

Those mutations which can prevail in the environment will be found at a later date - dying off means vanishing from the population.

So the question is how would not aging benefit the sustained success of a genetic conglomeration of genes in an ever changing environment ?

While you can not fundamentaly alter the programming of an adult individual organism ?

Longevity and aging are of no more concern to evolution as much as it affects the success / survival of the next generation while changing by selection as much as is required to survive.

You don't do anything for your offspring - you get the mayfly.

you feed the baby - bees.

you feed the baby and teach it - the cat which trains the kittens to catch mice

you extend on the training routine until you develop a culture which preserves survival techniques through the ages - homini

You need an ever extending life time to achieve this support to the next generation.

But from the point of self-reliance of the kids in their life there is diminshed evolutional pressure to keep the parents alive.

So longevity / absence of aging would be a fluke - if the old generation was not consuming ressources while still running an old inefficient set of genes and reproducing child generations with less adaptations than the current great-grandchildren.

So no aging would hinder the survival chances of the offspring.

Therefore longevity is selected for as long as the set of genes in the next generation is getting a benefit from the parents being still alive.

Immortality is actively negatively selected.

Aging is allowed by the diminishing effect of parental death on the survival chances of the offspring.