There's a creature I'm fascinated by, turitopsis dornii.

It's a jellyfish with unique biological powers.

When an adult turitopsis is injured or threatened, it can revert to its juvenile state, mature

and revert again, potentially continuing this cycle forever.

There are other organisms that also seem to live for extraordinarily long times.

In Utah, there's a colony of genetically identical aspentries that is probably endured for tens

of thousands of years.

In theory, at least some of these organisms are what scientists call biologically immortal,

which means they don't die of old age.

Of course, the only way to know for sure that they're truly immortal is if you yourself

are also immortal.

Aging and death have long been some of the biggest mysteries in biology.

Most biologists agree that aging is not an adaptive trait shaped by natural selection.

Unlike, say, the fins and tail of a fish, or a bird's nest building instincts, aging

does not give organisms any particular advantage.

But as some of the biologically immortal creatures show us, it is technically possible for

an organism to just keep living.

And if that's true, why aren't we all immortal?

I'm Ferris Jaber, and I'm a contributing writer for The New York Times magazine.

I wrote about human longevity and how we might stretch it even further than we already

have.

I also wrote about the ethics of a world in which humans live for multiple centuries and

...