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I understand (a little) that there are biological clocks and reason that after a certain amount of time organisms die. I'm wondering if that is something inherent in our DNA or in biology/chemistry in general. EG, is it possible that there could be a complex organism that would not die and would just regenerate it's cells In Perpetuam? I'm specifically interested in mammals and even more specifically interested in humans. But, I would be interested in hearing about other organisms like bugs, fish, plant, algae, etc.

I'm not asking if this practical, do we know how to do this, etc.. I just want to know theoretically if living forever is biologically possible, as far as we know. If not, is there an estimated upper limit?

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    $\begingroup$ en.wikipedia.org/wiki/Biological_immortality $\endgroup$ – Mithoron Mar 10 '15 at 15:13
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    $\begingroup$ It's definitely not practical. Lets assume an organism had evolved past disease and aging. It would still eventually die because with infinite time, the odds of it eventually falling into a situation where it runs out of food, or gets eaten, or dies in an accident go to 100%. So even an immortal species would still need to reproduce. If birth rates remain normal, but death rates are much slower, the population would explode, leading to many problems with food supplies and space and environmental issues. $\endgroup$ – user137 Mar 10 '15 at 15:45
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    $\begingroup$ @user137 - I'm not considering about practicalities. $\endgroup$ – Yehosef Mar 10 '15 at 16:01
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    $\begingroup$ This interesting post is very much related $\endgroup$ – Remi.b Mar 10 '15 at 19:12
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    $\begingroup$ @Yehosef "single organism" isn't that easy to define though. Do you consider aspen clones a single organism or not? They are considered as one of the oldest living organisms, and should be relevant to your question, even though they are in one sense a multicellular plant analog to bacterial clonal growth. $\endgroup$ – fileunderwater Mar 11 '15 at 10:26
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The immortal jellyfish can revert back to its immature polyp stage after reaching maturity, then mature again, over and over. You can read more on the wikipedia page, but this ability means it can potentially avoid senescence altogether.

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    $\begingroup$ It too will die when the sun becomes a red giant. $\endgroup$ – Joshua Mar 10 '15 at 22:46
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    $\begingroup$ @Joshua Technically, it will be boiled. But I can say this with certainty that it will surely die when you will disintegrate it into atomic particles. :P $\endgroup$ – arnabanimesh Mar 11 '15 at 11:40
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    $\begingroup$ @Joshua naturally, but it will fry, not senesce, and that's what the question is asking about ;) $\endgroup$ – C_Z_ Mar 11 '15 at 15:29
  • $\begingroup$ The cited wiki page cites one iffy reference, but the other is good, and available online: biolbull.org/content/190/3/302.full.pdf+html The authers of this article indeed claim that Turritopsis may be immortal (!!). Thanks for this great answer. $\endgroup$ – AliceD♦ Mar 13 '15 at 0:31
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    $\begingroup$ @Joshua It is considered Biologically immortal, meaning that it will not die as a result of cellular processes... That does not mean that an external agent can't kill it. $\endgroup$ – AMR Nov 28 '15 at 21:33
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You have a very interesting question there!

In order to answer, however, we must examine the most widely accepted "reason" for why we age and eventually die. Most scientists agree that it is because of mass cell death. Normally you and I would be able to deal quite well with mass cell death (such as a very large injury), the problem comes in when we are older because we cannot replenish them because we have physically exhausted our own supply of something called stem cells.

Most cells in our bodies actually cannot divide, so they rely on these stem cells (which can divide into any cell; think of them as a wild card) to replenish whatever cells die.

Sounds perfect, right? Not quite, each of us only have a given number of stem cells in our body (even though stem cells can divide into more stem cells, they usually don't). So the reason we age and die is because we "run out", if you will, of these stem cells and our supply of cellular replenishment is slowly cut off.

Back to your question, is it possible to stop this? Well you've probably already come to this conclusion by now, but theoretically if you could somehow supply the body with a constant number of stem cells, theoretically, you could live forever (or at least a really long time). This is evident, as you are aware, in flatworms, who have stem cells constantly circulating their bodies and are practically immortal.

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    $\begingroup$ Why do you call "running out of stem cells" the reason we die? It can just as easily be a side effect. $\endgroup$ – Slava Mar 10 '15 at 16:37
  • $\begingroup$ Sorry? Side effect of what? $\endgroup$ – CDB Mar 10 '15 at 16:40
  • $\begingroup$ Death process.. $\endgroup$ – Slava Mar 10 '15 at 16:41
  • $\begingroup$ That's what I have found to be the reason for aging in the time that I have studied it. $\endgroup$ – CDB Mar 10 '15 at 16:41
  • $\begingroup$ Oh, I see. I'm only saying that it is one reason for death, not all. Death can be caused by many things. $\endgroup$ – CDB Mar 10 '15 at 16:42
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Awesome question! It could use a couple qualifiers, however...

1) How do we define organism?

2) Are we assuming the environment never changes?

CactusWoman mentioned jellyfish that continually revert to an immature stage, essentially remaining young indefinitely. We could also cite colonial organisms. For example, some scientists say the world's biggest known organism is a fungus growing over an area of many acres (in Oregon, I believe). How long could something like that live?

Then there's the environment; as Joshua said, every living thing on Earth will presumably die when the sun dies.

And there's yet another thing to consider - dormancy.

Seeds that are centuries old have been sprouted. So would it be possible for a seed or spore to survive indefinitely?

In this spirit, some have suggested that life on Earth began when the planet was "seeded" by meteorites carrying life forms. A Martian meteorite that crashed into Antarctica created a sensation when it was announced that it might contain evidence of primitive life.

Whether or not the meteorite was "inhabited" is a matter of debate, and if life evolved independently on Mars, why couldn't it do so on Earth?

Nevertheless, to truly live forever - or even for a mere 100 billion years - an organism would presumably have to somehow escape its dying home planet and float in space in a state of dormancy...something that may or may not be possible.

P.S. I just discovered that the environment has already been discussed and pronounced irrelevant to this discussion. But I think it still makes for an interesting side discussion. ;)

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  • $\begingroup$ This is not an answer to the question. Please do not speculate or give open answers but answer the question. $\endgroup$ – Chris♦ Dec 13 '15 at 9:46
  • $\begingroup$ Please could you add some supporting scientific material that reinforces your answer and allows further reading. $\endgroup$ – rg255 Mar 8 '16 at 7:27

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