Subtitles section Play video
-
To us humans, aging seems inevitable - probably because no human has ever not aged. But getting
-
older isn’t as universal a fact of life as we might think.
-
Take the naked mole rat. Unlike their less-naked brethren, they don’t appear to age after
-
reaching adulthood - years pass, but the rats don’t get weaker, more susceptible to disease,
-
or wrinkly...at least not any more wrinkly...and they keep on making as many babies as ever.
-
Surprisingly, they aren’t any more likely to die in old age than when they’re young
-
adults. It’s as if they’ve found the fountain of youth, though perhaps not the fountain
-
of beauty. And naked mole rats aren’t alone in not aging: rockfish, lobsters, and bristlecone
-
pines also seem to stay forever young...or at least forever middle-aged.
-
We’re not exactly sure how these species do it, but their anti-aging secret may have
-
to do with their ability to rebuild the DNA caps on their chromosomes. These caps, called
-
telomeres, are one line of defense against aging in many species. That’s because cells
-
need to divide to replace old or dysfunctional cells, but each time they replicate, they
-
lose a little bit of DNA from the end of each chromosome. Normally that doesn’t matter,
-
since these lost bits come from the telomere end caps that don’t encode important information.
-
But after many replications, the telomeres get trimmed so short that the cells can’t
-
afford to lose any more DNA, and they stop replicating.
-
Age-defying species like naked mole rats, however, pump out high levels of a telomere-rebuilding
-
enzyme that enables them to keep on replacing old and dysfunctional cells indefinitely.
-
A few kinds of human cells make this enzyme, but the vast majority don’t. And even if
-
we could trick the rest into producing it, then we’d have another problem: more replications
-
means more chances for mutations that could turn a cell cancerous unlimited replication
-
increases a cell’s chances of becoming cancerous. Naked mole rats don’t care because they
-
seem to be immune to cancer; but we humans certainly aren’t.
-
However, as amazing as naked mole rats are, they can only pause their aging – the tiny
-
jellyfish Turritopsis dohrnii can age in reverse. Like butterflies, Turritopsis morph through
-
multiple stages during their life cycle. But unlike butterflies, if Turritopsis get wounded
-
or if times get tough, they can morph backwards, reverting to their immature polyp form until
-
conditions improve. They’re like, real life phoenixes.
-
However if humans could somehow imitate Turritopsis’ trick, it might not give us the kind of eternal
-
youth we’d be looking for… for one thing, melting into an amorphous blob where our cells
-
are reorganized and reprogrammed with new functions would not only be a mess; it would
-
likely turn our brain cells into skin or muscle cells - and vice versa - erasing our memories
-
and our sense of self. And no matter what, eternal youth wouldn’t
-
make us invincible - in fact, the longer a creature lives, the more time it has to get
-
chomped, starved, or smooshed. So eventually, every naked mole rat, pine tree, and jellyfish
-
will ultimately meet its end - because it’s possible to be immune to aging, but not to death.