I think there’s plenty of room for life extension

Evolution doesn’t optimise for length of life, just propagation. A number of species have evolved to have very short life cycles because that enabled greater propagation. Presumably shorter lives generally confer greater adaptability as it increases the opportunity for evolutionary change

Evolution does optimize longevity in at least one way.

Chromosomes have a limited number of telomeres, each time the cell divides the telomeres become shorter. If your cell runs out of telomeres it can't divide anymore. This is one of the primary mechanisms the body balances repair against cancer risk. Current max of human life is about 120. If you don't "solve" the telomere problem you are not going to extend life past 120, though you may have more people live that long and may improve quality of life in later years.

Our species has a good balance that lets us live well past reproduction age, presumably because there is evolutionary pressure (benefit) to having elderly people around to pass on knowledge, help raise grandchildren, etc.

You can do things that extend the telomeres, but that makes cells more likely to reproduce out of control (cancer). This is a very hard "problem" to solve because cell final death is so important in preventing cancer. We are not even close to solving this, it would require revolutionary biological understanding.

Couldn't there be 1:1 replacement of pretty much everything in the human body? Organs, bad/old cells for good/new ones...etc?

Nanobots at some point may be able to essentially destroy bad/old cells, and maybe feed/nourish good cells we want to keep, and when cells can't divide anymore, could those be replaced with ones that could ?

I think back to the movie Bicentennial man, where he made completely real working human / robot interchangeable parts that basically allow for increased life and better health. Sure it's a movie, but we can 3d print organs and things, so it's not outside the realm of possibility...

Think of telomeres like a counter at the DNA level. Each time the cell reproduces, it loses a counter. Eventually it runs out of counters and dies. To extend life you have to add telomeres. And you have to do it in an extremely careful way that still manages to control cancer.

In a sci-fi hypothetical where nanobytes can do arbitrary behaviors, sure, maybe they could intelligently do that. But that's an extremely complex thing.

My point to my original post is really that if anyone hears a "longer life" breakthru that doesn't even mention telomeres, I immediately move on. If they moved the needle on well-being of the elderly a bit, that's great. But nobody's "solving aging" without telomeres.

Telomeres are just the cell's odometer. Sure, rolling it back is good assuming that it extends the lifespan of the cell, but it still has the dents and dings it's picked up along the way from radiation & pollution, free radicals and oxidation.

This seems like part of the puzzle. First repair the damage, then extend the time span, and the more you do this the more opportunities you have to find an optimal solution.

I think the only thing that will actually work is for entirely new bodies to be built and for our minds to be copied over.

It's not immortality but that is probably as close as we will get, and once we can do that then extending our current body's lifespan will be exponentially easier.

Telomerase - an Enzyme found in Gamete and Stem (and Tumor!) Cells can reverse this Telomere shortening. Cycloastragenol derived from Astragalus herb can supposedly activate Telomerase - unfortunately it's very expensive to extract in significant quantities eg TA-65 costs $800 for 90 capsules. I tried it for a while and definitely noticed an effect, better skin, vivid dreams more energy. High cost and some concern over potential for Tumor promotion put me off continuing.

Evolution can optimize for longer lifespans if it makes propagation more favorable. It happened in humans — grandparents make us more successful. Except when they run our governments.

We need to evolve past the point where we expect to rely on government.

A benevolent Government is just Society. Nothing wrong with society.

Back to anarchy?

Some of our greatest leaders have been very old. Good and old are unrelated concepts

Great and good are also unrelated concepts. Google is a great company, but they decided “don’t be evil” is unnecessary for greatness.

Why would surviving longer in old age be adaptive? The trade-off could be as simple as "you're mostly infertile, any children you do have will have higher rates of genetic disease, and being healthier means you're alive and active enough to compete with your kids and grandkids for food and mates".

"It's more likely that there is some trade-off which we have not discovered yet."

Clearly some tradeoffs are less relevant today than they were to a tribe of cavemen. Even if grandpa is in great shape, he will have a hard time hunting thay wooley mamoth, and having him around too long will be too many mouths to feed.

Also it's hypothetically possible to give everyone a ripped physique without gym memberships, downside of this would be increased protein consumption.

> why hasn't any mammal evolved to start destroying them?

I think that evolution selects mostly for reproduction and not longevity. You don't have to live very long to have many kids (in like caveman / hunter-gatherer type of context as this is where evolution is basically), you just need to have great genetics. I guess sticking around for a few years after to protect the kids and provide for them is a bonus, but that part may be handled by the tribe too. But there's not much to be gained (from evolutionary point of view) from an individual living up to a 100 years or so.

There's doesn't have to be a major (from our perspective) trade-off if historically the benefit under selection was very marginal, probably somewhat more so both because of menopause and historical lifespans often being shorter.

Natural selection up to this point has prioritized for a good time, not a long time.

What? Immune cells attack the body all the time, how do you think you're not all cancer. It's only a disease when they attack useful cells too much.