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Comment by jes5199 | Hacker News Reader

this makes me think that telomeres are not the main cause of aging-related death. My mental model is: if you run out of telomere before you get old, you start to get disease - and that’s maladaptive. So there’s evolutionary pressure to slow down your shortening rate, up to a point. Once it becomes unlikely that you’ll outlive your telomeres, there’s no more pressure. So your telomere length + rate becomes a measurement of your species lifespan.

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> this makes me think that telomeres are not the main cause of aging-related death

That's an interesting argument, but couldn't you use the same reasoning to argue that telomeres are the main cause of aging-related death? The mental model I'm thinking is: As you run out of telomeres, you get diseases and you can't reproduce - and that’s maladaptive. So there’s evolutionary pressure to slow down the shortening rate, up to the point where you have children (plus grandchildren in the case of humans). When you're living long enough to have one or two generations of offspring, there’s no more pressure to correct the telomere problem.

Wouldn't your argument and mine be equally consistent with the featured article (that shortening rate predicts life span)?

If you lived longer still you might father more children.

Yes, but because of increased risk of disease and lower physical ability, you would also be a larger strain on your group/family. I think we should see this more as a survival of offspring and less as fathering more offspring.

There's probably pressure for species to not have longer lifespans. Youthful thinking and fresh perspectives are important. Wise old perspectives can get deeply ingrained and can't be changed easily. The free market for example experiences similar phenomenon where a new startup will outcompete a big old corporation. An industry that moves quicker (tech) evolves faster than one that doesn't (healthcare).

The evidence doesn't support what you imply: that older people can't learn or come up with novel ideas. Fresh perspectives are important, but there are more ways than ignorance (e.g. youth) to find them. For example, cross domain work often yields amazing new results; it's a great way to bring in fresh perspectives.

In evolutionary terms you become a competitor with your male offspring for reproduction, which may hinder natural variation.

This doesn't really make sense does it? There's only really evolutionary pressure up to the end of your child rearing years, no?

Should be context dependent. New parents benefit a lot from their own elder family members giving them advice on the basics; in an environment with less information (i.e. no internet), the advantage vs. people with no parents or family to help would have been substantial. So unless we expand the definition of “child-rearing years”, I think it could go either way.

for any amount of food, it's better to have an adult rather than an elder, for any particular gene.

So a truly optimal age system would have no old age at all, you will just die off after your children are self-sustaining.

Humans are double-viviparous species, meaning average grandparent lives past its grandchild's puberty. Humans are also atricial. These traits are shared by elephants, whales and dolphins too. However, humans are the only animal species those are triple-viviparous in occasions, meaning great-grandparent lives past its great-grandchild's puberty.

Human's average lifespans have been a lot shorter throughout history.

Average isn't that relevant. It's driven down by early childhood deaths & childbirth deaths (but after a point - menopause - childbirth deaths end).

Infectious disease killed many before old age. Antibiotics are a pretty recent invention.

Yeah, but the impact isn't that great.

According to Our World In Data [1] a 20-year-old would expect to live to 60 in 1850 (before penicillin), versus to 80 now.

[1] https://ourworldindata.org/life-expectancy#it-is-not-only-ab...

That's still long enough for a person to see their grandchildren reach and cross puberty.

Especially in a world where kids were born when the parent was in late teens or early 20s, rather than now when average age is 28 and pushing higher.

This means first grandchildren in early 40s (rather than late 50s), and first great grandchildren by mid 60s (rather than mid 80s)

And infectious disease was probably a much smaller problem for hunter gatherers living in small groups, which has been the case for the vast majority of our evolutionary history.

Historical average is relevant. I have an 18 year old cat. It's an aberration. We evolved under specific pressures. Only recently, have we removed specific age gates.

> There’s only really evolutionary pressure up to the end of your child rearing years, no?

No, at least according to some anthropologists and evolutionary biologists. For example see the Grandmother Hypothesis https://en.m.wikipedia.org/wiki/Grandmother_hypothesis

tl;dr might not be the bottleneck, so the telomere length and shortening rate is measuring something else that is.

If you do end up with telomeres that shorten very slowly, could there also be pressure to shorten them more quickly, so it really is just a measurement? Hypothesis: telomerase, which fights the shortening, also promotes cancer. I think I've even seen that before.

"Some experiments have raised questions on whether telomerase can be used as an anti-aging therapy, namely, the fact that mice with elevated levels of telomerase have higher cancer incidence and hence do not live longer. Telomerase also favors tumorogenesis, which leads to questions about its potential as an anti-aging therapy.[36] On the other hand, one study showed that activating telomerase in cancer-resistant mice by overexpressing its catalytic subunit extended lifespan.[37]

A study that focused on Ashkenazi Jews found that long-lived subjects inherited a hyperactive version of telomerase.[38] " https://en.wikipedia.org/wiki/Telomerase

Ambiguous.

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