5 ms·

It's not intuitively obvious at all, since each replication of our cells leads to our chromosomes getting ever smaller until presumably it starts eating into ge

It's not intuitively obvious at all, since each replication of our cells leads to our chromosomes getting ever smaller until presumably it starts eating into genes that do useful things. Unless it's intuitively obvious to you that you could live without genetic material at all, it seems quite obvious that -- given current biological processes -- there is a limit, even if that limit is longer than where we've gone before.

meowface 8y ago
There's the natural limit and the theoretical limit. In theory, some future gene therapy may swap out your chromosomes for ones that don't decay (while somehow not causing negative side effects) while you're still an embryo or gamete, and do all sorts of other things to make you nearly biologically immortal. And in some even more distant future, maybe consciousness upload (with the "copy conundrum" somehow resolved) will be a real thing, in which case living for thousands or millions of years seems plausible.
- bloak 8y ago
  That last case, "consciousness upload", means providing a new definition of "living". Nothing wrong with that, but worth noting, particularly since it's not at all clear what the new definition should be.
  - fjsolwmv 8y ago
    Yes, but it's not so discrete a difference. We change every second of our lives physically and mentally. We have ever increasing complexity of drug, surgical, and bionic therapies.
    - bloak 8y ago
      Running a simulation of a person would probably enable different kinds of change to be made, and some of those may be qualitatively very different from anything that has happened before. One also has to think about running multiple instances of a person, running a person in a non-real-time simulated environment, taking a checkpoint, restoring from back-up, and so on. At what point do you start to treat two instances of the same person as different people? If you stop running any instances of a person, have no particular plan to run one in the future, but you think you still have a snapshot in an archive somewhere, is that person still "living"?
bloak 8y ago
Even if it were the case that each replication made the chromosomes smaller (personally I would guess that there is a non-zero probability of them not getting smaller and even a non-zero probability of them getting larger thanks to a mutation) that would still only imply a hard limit on the number of replications. You would also need to find a hard limit for how long a cell can survive without replicating. Good luck with that. I content that there are no limits: however old you are, you have a non-zero chance of surviving another picosecond. The product of a finite number of non-zero real numbers is non-zero, therefore... Some people may wish to retort that at some point these numbers become so small that they are no different from zero in practice. Those people are probably not mathematicians. They're not wrong, either, of course, but they're not making a valid argument for there being a limit. There's no limit for the number of successive heads you can get when tossing a coin, either, though you won't in practice see more than a hundred if it's a reasonably fair coin. If there's no limit in that simplified, mathematical situation, does it make sense to hypothesise that "there is a limit" in the case of highly complex biochemical processes? This is all very philosophical. It doesn't help us to estimate the chances of a given person who is alive and 115 years old today (there seem to be about five of them) one day breaking Jeanne Calment's record of 122. Are any bookmakers taking bets?
- fjsolwmv 8y ago
  There are a finite number of protein molecules on a human, and a finite number of humans. Given a available days, ut is impossible to assign an accurate arbitrarily small nonzero probability of incremental survival. "Not being mathematicians" is exact what you want when making predictions about the real world.
- Declanomous 8y ago
  >Even if it were the case that each replication made the chromosomes smaller (personally I would guess that there is a non-zero probability of them not getting smaller and even a non-zero probability of them getting larger thanks to a mutation) that would still only imply a hard limit on the number of replications. The fact that chromosomes get shorter during DNA replication is a scientific fact. Chromosomes have padding at the end called telomeres that provide a buffer from the 'useful' DNA. There is an enzyme that can lengthen telomeres, and its of great interest to scientists interested in extending human life. There is almost no chance that mutations: a) regularly occur in such a way that makes the chromosomal DNA longer, especially in a way that offsets the base pairs lost during every transcription. and b) occur in the telomere area of the genetic code, after all the useful bits of DNA. If mutations did occur at a rate that would counteract the shortening of the telomeres, the rest of your genome would be mutating so quickly you would almost certainly die rather quickly. There are a whole host of other reasons why what you wrote is nonsense, and I don't have the time or the space to address them all. There is literally no fact to what you have written. It is clear you don't have even a rudimentary understand the biology of genetics. An understanding of math doesn't preclude the need for understanding the actual mechanism of how things work. The following articles are a useful primer to understanding the flaws in your reasoning: Okazaki Fragments: https://en.wikipedia.org/wiki/Okazaki_fragments https://en.wikipedia.org/wiki/Okazaki_fragments Telomeres: https://en.wikipedia.org/wiki/Telomere https://en.wikipedia.org/wiki/Telomere Telomerase: https://en.wikipedia.org/wiki/Telomerase https://en.wikipedia.org/wiki/Telomerase DNA Polymerase: https://en.wikipedia.org/wiki/DNA_polymerase https://en.wikipedia.org/wiki/DNA_polymerase DNA Replication: https://en.wikipedia.org/wiki/DNA_replication https://en.wikipedia.org/wiki/DNA_replication

meowface 8y ago

There's the natural limit and the theoretical limit. In theory, some future gene therapy may swap out your chromosomes for ones that don't decay (while somehow not causing negative side effects) while you're still an embryo or gamete, and do all sorts of other things to make you nearly biologically immortal. And in some even more distant future, maybe consciousness upload (with the "copy conundrum" somehow resolved) will be a real thing, in which case living for thousands or millions of years seems plausible.

bloak 8y ago
That last case, "consciousness upload", means providing a new definition of "living". Nothing wrong with that, but worth noting, particularly since it's not at all clear what the new definition should be.
- fjsolwmv 8y ago
  Yes, but it's not so discrete a difference. We change every second of our lives physically and mentally. We have ever increasing complexity of drug, surgical, and bionic therapies.
  - bloak 8y ago
    Running a simulation of a person would probably enable different kinds of change to be made, and some of those may be qualitatively very different from anything that has happened before. One also has to think about running multiple instances of a person, running a person in a non-real-time simulated environment, taking a checkpoint, restoring from back-up, and so on. At what point do you start to treat two instances of the same person as different people? If you stop running any instances of a person, have no particular plan to run one in the future, but you think you still have a snapshot in an archive somewhere, is that person still "living"?

bloak 8y ago

Even if it were the case that each replication made the chromosomes smaller (personally I would guess that there is a non-zero probability of them not getting smaller and even a non-zero probability of them getting larger thanks to a mutation) that would still only imply a hard limit on the number of replications. You would also need to find a hard limit for how long a cell can survive without replicating. Good luck with that. I content that there are no limits: however old you are, you have a non-zero chance of surviving another picosecond. The product of a finite number of non-zero real numbers is non-zero, therefore... Some people may wish to retort that at some point these numbers become so small that they are no different from zero in practice. Those people are probably not mathematicians. They're not wrong, either, of course, but they're not making a valid argument for there being a limit. There's no limit for the number of successive heads you can get when tossing a coin, either, though you won't in practice see more than a hundred if it's a reasonably fair coin. If there's no limit in that simplified, mathematical situation, does it make sense to hypothesise that "there is a limit" in the case of highly complex biochemical processes? This is all very philosophical. It doesn't help us to estimate the chances of a given person who is alive and 115 years old today (there seem to be about five of them) one day breaking Jeanne Calment's record of 122. Are any bookmakers taking bets?

fjsolwmv 8y ago
There are a finite number of protein molecules on a human, and a finite number of humans. Given a available days, ut is impossible to assign an accurate arbitrarily small nonzero probability of incremental survival. "Not being mathematicians" is exact what you want when making predictions about the real world.
Declanomous 8y ago
>Even if it were the case that each replication made the chromosomes smaller (personally I would guess that there is a non-zero probability of them not getting smaller and even a non-zero probability of them getting larger thanks to a mutation) that would still only imply a hard limit on the number of replications. The fact that chromosomes get shorter during DNA replication is a scientific fact. Chromosomes have padding at the end called telomeres that provide a buffer from the 'useful' DNA. There is an enzyme that can lengthen telomeres, and its of great interest to scientists interested in extending human life. There is almost no chance that mutations: a) regularly occur in such a way that makes the chromosomal DNA longer, especially in a way that offsets the base pairs lost during every transcription. and b) occur in the telomere area of the genetic code, after all the useful bits of DNA. If mutations did occur at a rate that would counteract the shortening of the telomeres, the rest of your genome would be mutating so quickly you would almost certainly die rather quickly. There are a whole host of other reasons why what you wrote is nonsense, and I don't have the time or the space to address them all. There is literally no fact to what you have written. It is clear you don't have even a rudimentary understand the biology of genetics. An understanding of math doesn't preclude the need for understanding the actual mechanism of how things work. The following articles are a useful primer to understanding the flaws in your reasoning: Okazaki Fragments: https://en.wikipedia.org/wiki/Okazaki_fragments https://en.wikipedia.org/wiki/Okazaki_fragments Telomeres: https://en.wikipedia.org/wiki/Telomere https://en.wikipedia.org/wiki/Telomere Telomerase: https://en.wikipedia.org/wiki/Telomerase https://en.wikipedia.org/wiki/Telomerase DNA Polymerase: https://en.wikipedia.org/wiki/DNA_polymerase https://en.wikipedia.org/wiki/DNA_polymerase DNA Replication: https://en.wikipedia.org/wiki/DNA_replication https://en.wikipedia.org/wiki/DNA_replication