There is no physical/chemical/biological reason you can’t live indefinitely with the health and vitality of a 25-35 year old. Aging isn’t a law of nature.
I think OP is not entirely incorrect. Reproductive cells undergo processes like epigenetic reprogramming, which basically strips away many of the chemical marks (like DNA methylation patterns) that accumulate with age. That’s one of the reasons babies don’t start with the cellular age of their parents. Researchers can take adult cells, reprogram them back to an embryonic like state using Yamanaka factors (a set of four genes) effectively erasing their biological age.
I think scientists currently are testing ways to "partially" reprogram cells to make them younger while keeping their function. Early studies in mice have shown some reversal of aging signs.
Seems like an engineering problem more than an absolute limitation.
DNA damage inevitably accumulates. The big reason children are younger than their parents DNA wise is because the parents' DNA undergo random recombination to create something that is the mixture of the two.
This doesn't help overall. Mixing two roughly equally broken things just yields the mean of the two. But the trick is that roughly 60 to 70% of conceptions will not survive to birth. This rejection sampling is ultimately what makes children younger.
If you had a population of single cells that didn't undergo this rejection sampling at some point, entropy and Muller's ratchet would actually age the entire population and kill it.
You are right that DNA damage inevitably accumulates and that selection (including miscarriages) weeds out embryos with severe defects but that doesn’t fully explain why a newborn’s biological age is near zero.
What scientists usually mean by "cellular age" isn’t mutation load, it’s the epigenetic and functional state of cells. During gametogenesis and early embryonic development DNA undergoes extensive repair, telomere maintenance and global epigenetic reprogramming that wipes and rewrites methylation patterns. This resets the cellular "clock" even though some mutations are passed on.
So while mutation load drifts slightly each generation, the reason babies start biologically young is this large scale reprogramming. That’s also why researchers are trying to mimic this process in adult cells (Yamanaka factors etc) to reverse aspects of aging.
Fully agree! I don't think life is much more than a sort of chemical engineering, "designed" with the "purpose" of self-replication. Our engineer, natural selection, didn't have "healthspan" in mind; insofar as we are human-making machines, we're pretty well built. I fail to see any reason that necessarily precludes a retooling of our internal machinery to accomplish our desires, not nature's.
More over, babies can clearly grow from limited cells to "young" versions of fully differentiated human tissues. Which means from some initial stock, you can replace the vast majority of the bodies cells with younger versions - i.e. with plausible, attainable technology we would generally expect to be able to grow immunologically identical replacement organs and major tissues. That definitely is an engineering problem, more then anything else.
The only truly troubling one is the brain, and we're very much not sure if it actually is one or for example, suffers degradation from the degradation of the body its attached to - likely both - but we also know that the brain is not a static structure, and so replacement or rejuvenation of key systems would definitely be possible (certainly finding any way to protect the small blood vessels in the brain would greatly help with dementia).
Social shaming is a big way humans deal with unchangeable things. They impose a cost for anyone expressing a desire for that thing to be different.
And it makes sense, really. You can't have a functioning society if everyone is running around freaking out about death all the time.
But we're entering a weird time where we might actually be able to add more good years to our lives. One of the steps towards getting there is being a little more okay with people seriously exploring these ideas.
> If not, the point in doing that is the enormous amount of suffering you create while thrashing against an inevitability.
This is absurd. Of course mortality is inevitable -- eternity is a very long time -- but working to increase lifespan, prolong one's youth and vigor, and delay the inevitable doesn't cause an "enormous amount of suffering" (far less than the diseases of aging cause) and it's unfair to characterize it as "thrashing" when it can be approached in ways which are thoughtful and reasonable.
You aren't wrong. I was replying to a flippant declaration "I don't see the point [in coming to grips with mortality]", which is quite different from your nuanced reply.
I tried to convey that I'm not saying "this is as good as it gets and it's wrong to try for longer life". Your "thoughtful and reasonable" approach was exactly what I had in mind.
What I say leads to suffering arises from denying that mortality is inevitable and tarring those who say otherwise as defeatists. Death is another part of life, as you acknowledged. It unnerves me to see denying that truth cast as a virtue.
This is unfair, and akin to branding anyone who takes medicine as being unhinged.
There is evidence we can extend our health spans. By how much and how are open questions. And if we can actually stop aging, versus slow it down, has not been demonstrated. Some people engage with this unhealthily, just as many terminally-ill cancer patients unhealthily engage with long-shot treatment options. That doesn’t make everyone taking those treatments delusional.
I’d hope we more mature as a society than decrying real medical research that could materially increase our health spans because they’re heretical.
It's the 'indefinite' part that I react negatively to. I don't have a good impression of people who are obsessed with abolishing death, as opposed to your example of maximizing quality of life (or minimizing illness) without getting too hung up on overall age.
Actually they said: "Aging isn’t a law of nature." But it kind of is. Almost all biological organisms age and the ones that don't are much simpler than us. That's not to mention entropy which is both a law of physics and dictates an inescapable form of aging for the universe as a whole.
They also said there isn't a physical reason, that is often meant to mean "it isn't a law of physics".
The fact that something happens doesn't mean it's a law of anything. Cars didn't exist before we built them - no law of "no cars". People died of TB before we had a cure - no law of "TB". Same for various types of cancer.
In practice when someone says "live forever", they don't mean to imply they'll live the 10^100 (or whatever the guestimates are) years to the end of the universe. They mean they'll stop aging in the sense that we do now. Maybe we could live to 10,000 or 50,000 or whatever. You can always get hit by a bus, or get some strange disease from a bat, or whatever.
We have been trying since medicine existed. Granted we can see much further now thanks to modern knowledge and tools, but we still can't see far enough to identify the causes or even speculate about actual solutions to aging. For all our technology and medical knowledge, getting somebody to live past 100 is still 95% a mix of genetic lottery and the chance of not developing too serious of cancer until really late.
The vast majority of medical spending is on treatment of illness/problems and always has. Very little money is spent on actually understanding and figuring how to pause aging itself.
This is not true and easily countered by any sort of investigation.
Lobsters, flatworms, immortal jellyfish and hydras are all believed to be immortal.
In fact we know how to live forever, control our telomeres. We know it works because cancer exists. We just can’t control it but controlled cancer is effectively immortality.
Cancer is a parasitism that kills the host (or the host dies from other causes and it is not self-sufficient). Just because something is defined by uncontrolled self-replication doesn’t mean it is stable to live forever (Which is as much a comment on homeostasis as self-renewal)
[EDIT: Biologically] immortal doesn’t mean indestructible. It just means they don’t age.
Lobsters aren’t truly biologically immortal. They “continue to grow throughout their lives,” with “increasing amounts of energy” being needed to mount ans they grow larger [1]. “Eventually the cost is too high and lobsters can die from exhaustion.” (That said, if our cells aged like lobsters we’d live something like thousands of healthy years.)
For true biological immortality, look to some jellyfish [2]. You literally can’t tell if a cell is taken from an old or juvenile.
> Immortal doesn’t mean indestructible. It just means they don’t age.
Technically “immortal” means “never dying”, it has nothing to do with age. You could be unable to die but continue to age and become ever more decrepit (although the Oxford dictionary does list “never decaying” in its definition), for sure there’s a sci-fi short story about that out there.
The mentioned creatures all age, they do get older, it just so happens their bodies don’t deteriorate, or they do but regenerate.
That’s the second paragraph. I was specifically addressing only the first (the one I quoted). In that one you seem to be saying that “immortal means not aging”. That’s the only part of your post I wanted to address, the rest was very clear.
Lobsters die of old age when they fail to molt, become trapped in their shells, and starve. The lobster body plan does not scale indefinitely. Presumably at a certain point they'd boil in their own metabolic heat.
> What is the oldest known living individual for each of these species, and for how long are they alive?
For the jellyfish, we don’t know. Their cells are indifferentiable by age and they’re bastards to study, with only one scientist in Kyoto having managed to culture them [1].
> no physical/chemical/biological reason you can’t live indefinitely with the health and vitality of a 25-35 year old
We don’t know this. We know of no creatures as biologically complex as humans that demonstrate biological immortality. That might be because nature never bothered. It might be because it can’t.
But you are generally correct: we have strong evidence healthspan-increasing interventions are not only possible, but proximate. That research could move faster with more funding, particularly from the public, since if we relinquish this funding to the rich it will not prioritize treatments which may be slightly less effective but much cheaper and thus broadly applicable.
(1) Yes we do have an example: us. Why is a baby’s cells young and healthy, and not the age of the parents? Dormant eggs are not the answer as you’d still get accumulating damage over time. Turns out there are mechanisms for cellular reprogramming which rejuvenates cells. There are mechanisms for making ages cells indistinguishable from young cells. We just haven’t fully harnessed this capability on therapeutics yet.
(2) The deeper point is one of logical necessity. No bird flies faster than the speed of sound, yet that doesn’t work as an argument for the impossibility of the SR-71 or Concorde. No physical law prevents restoring tissue to healthy young state. We just haven’t developed the tools to do so (yet).
> No physical law prevents restoring tissue to healthy young state. We just haven’t developed the tools to do so (yet)
You’re speculating too far beyond what we know to speak so definitively. Plenty of biology and even thermodynamics suggests there may be limits. That doesn’t prove they exist. But it’s in the same category as saying there are no know physics which prohibit time travel or transcending the human condition into a state of pure consciousness. Like, sure, there aren’t, but to use your analogy, ancient Romans didn’t know about the speed of light.
The difference between healthy young cells and diseased old cells is no more or less than the difference in configurations of atoms.
Diseased old cells have accumulated damage in a multitude of different forms, as well as accumulated junk. Fix the errors and remove the junk. It is as easy and as hard as that.
Nothing in thermodynamics or organic chemistry prevents this from being possible in principle.
You can't invoke thermodynamics, because thermodynamics doesn't work that way - the Earth is not a closed system. The sun continuously imparts a stupendous amount of energy to the planet, sufficient to allow the entire biosphere to continuously replace itself.
Thermodynamics is not a limit on an intelligent agent reconfiguring atoms on Earth for the next several billion years.
It doesn’t really matter. If you can exist as a 25 year-old, there is some change you can make to your body and cells that will indefinitely preserve that. It may not be within our grasp for maybe even up to another century, but it truly is inevitable.
Assuming no proton decay, its life span (for baryonic beings such as us) is far beyond 10^1500 years, so I don't think that "lifespan of the universe" is a limiting factor here. Nobody's speaking of living an infinitely long life.
I'm not saying this isn't possible, as some simple lifeforms seem to be basically immortal but our systems are much more complex and consist of many more moving parts and we are just meat machines. Machines wear out and you have to replace the parts. We're no where near being able to replace all of our parts. So there is a pretty good reason why at least the people currently alive aren't going to see what you're saying come to fruition. Entropy is a bitch.
> isn't telomeres a physical/chemical/biological reason we can't live forever?
It’s one component, but not the only reason [1].
Naked mole rats’ telomeres do “not shorten with age but rather showed a mild elongation” [2]. They are long lived, for rodents, and don’t degrade into balls of cancer [3]. They nevertheless age.
There are a handful of animals, mammals even, that essentially don't get cancer (some/all large whales and naked mole rats IIRC). So that might be solvable other ways.
And I wouldn't expect it to be, given that were are the product of billions of years of an evolutionary process that has relied on 'scrap and rebuild from scratch' as a mechanism to control errors.
Physical/chemical maybe not, but biologically there might be strong reasons to not allow a complex organism to live forever. Evolution might be accounting for a lot of the reasons leading to the death of the individual organism. For one it would stimulate evolution itself and also alleviate the inevitable resource pressure.
A species that lives forever must adjust to reproduce relatively slowly to not overwhelm the local environment. A species that lives short lives will reproduce at much higher rates. So at any time the fewer “immortal” individuals would be vulnerable to competition from the many “mortals”, or to predators.
Humans are a special case because we don’t operate only on biological imperatives so you could make immortal humans but with implications we can’t even think of now. Maybe our limitation will not be biological but societal.
You are mixing up evolutionary incentives with real chemistry-driven biological constraints. The base incentives of reproduction-driven natural selection may make aging inevitable under natural selection, but that says nothing of artificial selection or bioengineering.
> You are mixing up evolutionary incentives with real chemistry-driven biological constraints
> but that says nothing of artificial selection or bioengineering
Feel free to be specific. Start from here and describe your revelation about my “confusion”:
>> Humans are a special case because we don’t operate only on biological imperatives so you could make immortal humans
Natural life o overwhelmingly selects for well defined, limited lifespans. Engineered human life likely won’t see any natural pressure but rather societal pressure to set a well defined, limited lifespan.
There’s a well-known short story called “ The Fable of the Dragon-Tyrant” meant to reveal how ridiculous and nonsensical society’s attitude towards death is. You seem to be taking the opinion that the society shown within, in which death is artificial and societally enforced, is ideal and something to emulate.
I truly don’t know how to respond to this. If you want to die on a rigid time table, fine. Don’t take the rest of us out with you.
