[spwa4]

Because you can reset the clock, and even sabotage it. In fact, that's how we produce a certain class of medicine (by now probably 10 classes of medicine, but ...)

Also, there Henrietta Lacks, died in 1951 of metastasized adenocarcinoma, but "still alive":

https://en.wikipedia.org/wiki/Henrietta_Lacks

[Retric]

By that token normal reproduction qualifies as immortality as parents share a lot more DNA with their kids than those cell lines with their originator. Biologically those cell lines are generations of new organisms not the same individual living indefinitely.

Further those cells can’t compete out in a forest somewhere. Going multicellular means optimizing in ways counterproductive to survival on their own. But failing to cull off defective cells means you can’t have a functioning multicellular life form, thus making this a dead end.

So no in nature there isn’t some switch that means those cells get to survive indefinitely. The closest viable option is as an infection shared among very closely related organisms, but that’s not a stable option which means it’s really rare in nature.

[spwa4]

> By that token normal reproduction qualifies as immortality ...

As a kind of immortality, yes. It's not even just DNA, it's actual cells that were part of the individual that stay alive beyond any age limit.

Does it keep the full individual organism alive? No.

[Retric]

My point is because it doesn’t qualify at the organism or cellular level this doesn’t either.

> actual cells that were part of the individual that stay alive beyond any age limit

Neither the egg or sperm or egg cell survive to birth. Only descendent cells with wildly different DNA do.