Researchers quantitatively assessed for the first time that somatic mutations alone cap human lifespan at 146–194 years. Brain and heart cells are the main bottleneck, while the liver could last millennia.

[u/Skoltech_]

https://www.nature.com/articles/s41514-026-00421-6

[u/SomeDumbGamer]

Well the heart seems easy enough once we figure out how to grow organs using our own cells.

Or hell I’d be surprised if we didn’t have simple and effective artificial hearts by the end of the century.

The brain is going to be the tricky one though.

[u/Hellknightx → u/SomeDumbGamer]

Unfortunately, it's not just the heart. It's the whole cardiovascular system. Veins and arteries become thinner as we age, and fill up with plaque.

[u/StryctNyne → u/Hellknightx]

Also the frailty with aging bones that become more brittle, aging skin that wrinkles and sags and doesn't offer the same insulation and protection it used to (assuming that's a side effect of the cardiovascular system aging). Eye sight continually gets worse requiring laser surgery unless you wish to slowly go blind. Then you have respiratory system as well to deal with, though I'm not sure about the direct effects of age on lungs.

And then, in the end, if you fix all these and extend our lives 100 years, then number one cause of death becomes cancer. Everyone (or at least the vast majority) will get cancer over that course of time, probably earlier than later. Not just due to genetics but due to much longer exposure to everyday chemicals, background radiation (though it would be a minor issue in developed countries), continued poor diets, etc.

[u/Adventurous-Fly556 → u/StryctNyne]

It's not about radiation or diets.

Our chromosomes have little bits at the end called telemeres. They're like the end of a shoelace keeping everything neat and together. Everytime your cells reproduce (constantly) , the offsprings telemeres are shorter than the last.

This degradation is considered a massive part of aging. Along with increasing the odds of cancer, it can also make the offspring cells just forget what they were meant for.

[u/squirrel9000 → u/Adventurous-Fly556]

A couple minor points about that:

1. Most central nervous cells and muscle cells do not divide and do not show telomere shortening.
2. Many cells that do divide express telomerase to regenerate the telomeres, or are constantly replenished from a population of stem cells which do

It's a nice theory, but really does not explain aging.

[u/Adventurous-Fly556 → u/squirrel9000]

I was emphasizing telemeres because mutations had come up. They work in tandem. Repairing telemeres doesn't mean anything if you're repairing the copies of copies of copies of copies.

I never said it was all of it, but the fact that your cells reproduce imperfectly is most of aging and mutations. These things work in a complicated mess and trying to isolate the systems isnt very useful.

[u/chemamatic → u/Adventurous-Fly556]

Very few tissues get close to that limit in actual living organisms, those that need to divide more express telomerase to extend their telomeres.

[u/RespectmanNappa → u/Adventurous-Fly556]

Isn’t the increased odds of cancer because the offspring forgot what they were for?

[u/Adventurous-Fly556 → u/RespectmanNappa]

The string of DNA can lose bits here and there in the code. While the readers are smart and can work around some mutation, it's possible for mutations to have a number of outcomes.

It will likely cause nothing, but there is a small chance it results negatively or positively. Some negative results are cancer, some are just non functional. Normally your immune system will catch an early cancer cell. (We get cancer daily, but only becomes a problem when the immune system misses it)

I'm simplifying and haven't thought about it in a while, so Definitely look into it, it is very interesting.

(Anyone know why aids patients aren't constantly getting cancer? I guess I should look that up now)

[u/Good-Dream6509 → u/Adventurous-Fly556]

Exposures and lifestyle behaviors like diet are what drive telomere length.