Ask HN: If agelessness was genetically possible, wouldn't it have evolved?

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.

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.

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.

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).

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)

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

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.

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

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

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.

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.

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.) [..]

I think the key to vertebrates not unlocking the secret to immortality lies in our mode of procreation which is sexual reproduction that requires two sexes.

I have always wondered..if gender a mutation?

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.

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.

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 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...

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.

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.

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.

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.

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.

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.