New research reveals longevity gains slowing, life expectancy of 100 unlikely

What theory says that human lifespan has no limits with technology assistance? Anything involving replacing biological systems with artificial ones is not really extending human lifespan, it’s replacing human life with something else.

If you had full understanding of human cell and how they contribute to homeostasis, you could reprogram the cell to rejuvenate them endlessly without turning into cancer (many cancers have unlimited lifespan). You would also need to find ways to remove all cruft that gradually accumulates even in healthy body, like heavy metals etc.

I won't touch on whether or not you're still you as you replace your biological components with artificial ones.

But who says that's the endgame? Presumably an advanced enough medical technology could remove the internal byproducts of aging, and get your cells to stop dying / running out of steam / going cancerous. Obviously we have no idea how to do that, and maybe we never will, but it seems plausible.

How do you know that you could? That’s the question! If we did understand biology perfectly it may be that we would then prove no organism can live forever and reproduction is the only way.

Because there's absolutely no reason to believe that's the case? Like I don't know what the point of this argument is: maybe it's impossible. Sure, great. Okay. But you know...let's actually find out, because it looks very possible if hard from our current vantage point.

There's also no reason to believe the opposite is the case.

> Like I don't know what the point of this argument is

The point of the argument is to stop people like you from making declarations about what is possible without any evidence

> Sure, great. Okay. But you know...let's actually find out

Can you show me where anyone said we shouldn't find out?

> because it looks very possible

There's absolutely no reason to believe that's the case

Reproduction is not physically special. If it is physically possible to create a new organism with a longer lifespan than its parent (which it is), then it is physically possible to extend the lifespan of an existing organism. This may be impractical, but we cannot prove that no organism can live ≈forever, because it's not a physical impossibility. (Assuming a source of power remains present: it looks like the universe won't last forever, so we can trivially assert that no organism can live forever.)

This is perhaps the single worst form of argument I've ever seen. It does not help, it does not engage with anything scientific, it doesn't promote any new ideas (an example of an idea worth exploring is 'how can a cancer cell live indefinitely but other cells cannot' or 'why do different animals live for different lengths of time and what triggers this process'?). Things not worth exploring include whatever you're engaging in.

Do you believe this limit on lifespan is a uniquely human condition? or do you believe that it's impossible for any animal whatsoever to have a long lifespan (let's say 400 years for the sake of argument here).

Reproduction doesn't create whole new cells from nothing (except in the ship of Thesius sense). It's existing cells getting reprogrammed to do new things.

Reproduction does result in new matrix/scaffolding being built but the cells build that (and can rebuild it if so directed).

Of course some things "we" care about exist exclusively in the matrix (configurations of neurons, learned behaviors, memories, etc) so that could well be a limit for those parts of the body where we care primarily about preserving the matrix.

Anyway my point is that "reproduction" doesn't create whole new life, it's just a continuation.

Some cells are literally hundreds of millions of years old.

That’s not forever and it required a very specific environment, but biological degradation on that timescale can be effectively zero.

You know what a chaotic system is, don't you? That goes for a simple double pendulum.

There is no "full understanding" of a complex system.

We know it’s possible for living things to be functionally near immortal.

We also know germ line cells can give rise to new organisms which can give rise to germ line cells in an unbroken chain effectively forever.

This is quite far from making a human immortal but it shows that there appears to be nothing in physical law or intrinsic to biology that prohibits it. Therefore it is possible.

Star travel and terraforming Mars are also possible. Possible does not imply anything about difficulty. We don’t really know if radical life extension or borderline immortality are fusion hard, quantum computing hard, or starship hard.

You can replace almost whole body and its still you as the mind. But once you replace brain then its just a copy, you can't literally move biolectrical complex that makes us into silicon in any possible way. And brains age like the rest of the body, telomeres issue applies too.

The best possible outcome would be watching your digital copy having digital life, while you yourself wither away regardless. More akin to having a child than oneself preservation. Not really something special, having physical children still beats this.

If you could put your mind in a robot, is it still you? What if you get a knee replacement? What if you infuse a young persons blood? What if you put on a contact lens? Fun questions, but I’m not sure the answer changes what we will do much.

Two issues here - the first is that relatively new discoveries like the bidirectional gut-brain axis, and the major effects it has on you, pose a technical issue to traditional thought experiments like brains in a vat (or robot as it may be). The second is that this also doesn't really answer the question. Your brain, like everything else in your body, degrades over time. It's not like it becomes immortal if you just stick it in a robot, if that were even possible.

> We know it’s possible for living things to be functionally near immortal.

Not in any sense that's applicable to humans.

The often-cited animal examples, like greenland sharks, tortoises, and lobsters, are slow-moving ectotherms with "cold" metabolisms. Adjusting for watts per unit mass of biochemistry, they might "live" less in all their centuries than you do in a single decade [0-3].

In that sense they're only "long-lived" in the same way a tree is long-lived. Yeah, it might not die. But it's also not doing much that produces wear and tear, misfolded proteins, scar tissue, plaque buildup, etc.

Microorganisms and cnidarians, which can be truly immortal, are even more divergent. For example a common form of "immortality" involves periodically regenerating body parts by reverting to stem cells. IIRC regeneration is ancestral to all animals, but mostly lost in mammals.

Humans can actually already regenerate to a limited extent [4]. But how are you going to regenerate an entire primate nervous system (which "immortal" animals don't have), without losing everything you are?

In fact, the use of regeneration to achieve "immortality", and even that only rarely and in very simple animals, suggests it may not be possible at all for living organisms to live indefinitely in the same body. Otherwise, why would evolution waste calories rebuilding a whole body?

I suspect some systems-theoretic effect like the Red Queen hypothesis [5], but on a micro scale. Change is the only constant, and immortality implies trying to stay the same when the only thermodynamically favorable options are to grow or decay.

  0: https://www.nature.com/articles/s41598-020-76371-0
  1: # Greenland shark metabolism over entire lifespan
     sh -c "units '((30mg/oxygen)*(mol/g))/hour/(1000/1000^0.84*kg) * (434kJ/mol) * 200year' MJ/kg"
  2: # Greenland shark lifespan metabolism, alternate estimation
     sh -c "units '192kcal/day*200year/126kg' MJ/kg"
  3: # Human metabolism over 1 decade
     sh -c "units '150W/100kg*10years' MJ/kg"
  4: https://en.wikipedia.org/wiki/Regeneration_in_humans
  5: https://en.wikipedia.org/wiki/Red_Queen_hypothesis

yes precisely. that's why I picked 400 years

I mean I also feel like people would be pretty happy with the average lifespan of a tree, or a Greenland Shark, etc.

Also, some few (fairly primitive) animals are "biologically immortal," for example, lobsters (which are motile and vaguely resemble us more than, say, sponges and jellyfish) don't experience senescence.

That being said, I think we have a long way to go if we want to make any progress at all, and I doubt I will live to see it.

I don't think regeneration of bulk tissue is what people are generally talking about when they talk about immortality. Rather they talk about there being advanced homeostasis from yesterday, to today and to tomorrow under "normal" living condition. The point is not that you should be able to regenerate from blowing your brains out.

Ship of Theseus it. Slowly replace the brain bit-by-bit, taking breaks in between. For each component, use three in a democratic redundancy (for future maintenance).

I wouldn't personally do that unless I was already dying. But, I see no reason believe it wouldn't preserve the soul. Your organic brain is already doing it all the time on a small scale.

Yep. The point I'm making is that there is no precedent in nature for a complex animal maintaining homeostasis indefinitely like that (that doesn't rely on bulk regeneration). And given such immortality would presumably be highly evolutionarily advantageous, there is therefore no reason to believe it's possible at all, and many reasons to suspect it might not be (antagonistic pleiotropy, chaos theory, thermodynamics…).

Aren't some trees, some fungi, some sharks and some crabs basically exactly that? They are most certainly complex life. Sure you are right heir metabolic profile is very different.

But really the your argument is already shifting to "there is no life ver similar to humans that do it, so it must be impossible" which imo is a much larger stretch then assuming it's possible.

> Anyway my point is that "reproduction" doesn't create whole new life, it's just a continuation.

Then you're just arguing that we're already immortal, after all we reproduce, but I don't think that's what we're talking about when we talk about longevity. Longevity is the continued existence of a particular being, not its continuation through descendants.

> it is physically possible to extend the lifespan of an existing organism.

This is not at all guaranteed until we actually manage to do it. And that's exactly what we're discussing, you can't just say "but it must be possible". There's no rule of the universe that says it should, and given life has been around for 4 billion years and there's no single species (specially animals which is what we really should consider here if we're talking about human lifespan) that manages to live for more than a few hundred years, I think that's strong evidence that life is approaching a fundamental limit here. Someone else said "maybe that's enough" - well, why?? Maybe 100 years is already quite enough then??

> Because there's absolutely no reason to believe that's the case?

The fact we haven't seen an organism live forever is strong evidence that that's the case. You're the one making the case without any evidence!

We aren’t much more complex than a crab, if we are at all. “Complexity” is not what makes us what we are. It’s that we went down an evolutionary path that heavily leveraged intelligence and social cooperation so we got a big hypertrophied brain. Our brain is like a cheetah’s musculoskeletal system or a rabbit’s reproductive system.

The OP is also massively underestimating plant complexity. We aren’t much more complex than a tree either.

We are higher metabolism than both though, and with that the OP has a point. We are already long lived for a high metabolism animal. Our metabolic rate makes it harder for our repair mechanisms to stay ahead of oxidative and radiation damage. That will make extreme life extension hard for us, harder than if we were reptilians or arthropods.

Take the existing organism apart, fix all the problems, put the organism back together. No laws of physics prevent this, so by the totalitarian principle it's physically possible. Principles of engineering might make it impractical, and even if it is practical we might never discover how to do it, but it's possible.

The point is that a fundamental assumption that "reproduction" does anything that can't be done by regeneration is just a hunch that so far isn't actually supported by anything in microbiology. The existence of reproduction is irrelevant to the question.

> This is perhaps the single worst form of argument I've ever seen.

It's because you didn't understand it

> 'how can a cancer cell live indefinitely but other cells cannot'

Cancer cells are damaged cells mutating without regard for function. It's pretty obvious that there is a difference between "living indefinitely in a mutated form devoid of original function" is different from a cell performing a specific function

> Do you believe this limit on lifespan is a uniquely human condition

No

> or do you believe that it's impossible for any animal whatsoever to have a long lifespan

Let's pick an arbitrary timeframe and declare that as long

No, I don't think anything is impossible when you pick dates "for the sake of argument"

if you claim to think that 4x your current max-ish lifespan isn't long, then you're not having an argument in good faith, are you?