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Comment by blago | Hacker News Reader

I think immortal is the wrong word here. All organisms die. If it's not aging, then decease and predators will do it.

Biological immortality is the technical term for organisms which do not die unless killed, or more accurately where rate of mortality from senescence does not increase with chronological age.

Ah, I didn't know that. Thanks.

I thought the term was negligible senescence?

They're similar but distinct concepts. Negligible senescence means after a point aging doesn't negatively affect the organism. They don't lose reproductive capability or experience functional decline. Imagine being 20 forever.

Biological immortality means after some point mortality rates don't increase with age - you can still grow old, it just won't directly kill you. Biologically immortal organisms don't have a max lifespan, if they're lucky they can just keep on going, but they may be dramatically more feeble than their younger counterparts.

I think some Lobsters and Crocodiles are in the later category. Immune to cancer, their cells divide without limit over the years. So they never stop growing. The enormous ones are the oldest, and have a size fitness advantage in hunting and other combat, but a counter balancing fitness disadvantage in their increased needs.

I'm not aware of a context where immortal refers to organisms that can't be killed by accidents and predators. In mythology and novels alike, vampires, gods, elves, ..., are all called immortal and still can be killed.

It's called Biological Immortality[1] and there are a few examples of animals that are considered immortal.

[1] - https://en.wikipedia.org/wiki/Biological_immortality

I thought crocodiles or alligators (forget which one) were immortal and they tend to die only because they get so big and can't eat enough to maintain life eventually. But, they're not on this list?

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