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Comment by beefield | Hacker News Reader

> . We are essentially living past our primitive life expectancy until something fails which is very recent and evolution has had little time to catch up to this.

To my naive understanding of evolution, it has little incentive to fix anything that breaks after reproduction age. So I would not expect evolution to catch on cancer ever.

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In particular for primates, the elderly help the community and this is obviously beneficial for survival and reproduction.

>> he elderly help the community and this is obviously beneficial for survival and reproduction.

To a point. There is an inflection where the grandparent benefit becomes a burden on reproduction and survival. From a purely evolutionary perspective, this would probably occur where the presence of elderly people starts to impact the number of children born. We are seeing that today as many younger people are burdened with taking care of elderly relatives rather than raise children.

Many?

How many people of childbearing age have elderly parents?

By the time parents are elderly (60+, generally 70+ for needing substantial care) , children are already born.

There are parts of the United States where the average age of a woman when she has her first child is 30. All things being equal, that would make a first-time grandparent 60 years old at the birth of her grandchild and over 80 at his college graduation.

Especially given how insanely long our child rearing process is compared to other species, and how as we get more sophisticated it seems to get longer...

One can easily argue that evolution needs also somehow get rid of the elderly at some point.

easily but perhaps not convincingly

"needs" is a strange term, as is "get rid of". In nature, an organism generally doesn't need to "get ride of" anything that isn't actively feeding off it -- The state of nature is for weak organisms to die on their own.

But people never select for "good" elderly so to speak.

Neither do most primates or lions. The elders just happen to be there. So we can't really even say if it's just more elders in the animal kingdom making themselves useful. Which, again, is happening after reproduction typically.

For something to have an effect on reproduction, I would think it would need to be part of the decision beforehand.

These sorts of selections are likely to happen on a group level to the best of my knowledge, and you can easily imagine how selection for good elderly could work if you imagine children's life expectancy being dependent on their parents and grandparents. If (hyper simplified) a mutation that allows people to maintain eyesight for an extra 10 years helps them be extra spotters for the family on the hunt, and in a food scare environment, making one kill is life or death for the children's ability to eat, then that lineage with better eyesight could be selected for

This is kin selection, not group selection. It only works for near relatives, since shared gene content drops off exponentially with each relation.

Direct fitness is not the only way natural selection favours individuals. Genes that make individuals past their reproductive age turn into good caretakers (including genes that improve their health) are more likely to increase their frequency in subsequent generations (through the descendants they care for). This is called kin selection.

Kin selection. The elderly can help their grandchildren survive, so genetic predispositions towards living longer and helping your grandchildren can propagate depending on the cost-benefit of that strategy.

Likely a very new concept on an evolutionary timescale, and competing against the survival chance cost of more mouths to feed during an acute resource shortage.

It seems absolutely not a coincidence that the much faster, by orders of magnitude, process of human history got set in motion at a time when grandpatenting, as an evolutionary concept, wasn't quite finished yet.

Absolutely not a new concept, kin selection is why parents care for offspring.

Parents caring for offspring (vs spray and pray of hundreds of eggs) is very new on evolutionary timescales.

If by "very new" you mean 250M years, then maybe.

The elderly would have to specifically help their own grandchildren, not just the community, for evolution to have an effect (otherwise you’re talking group selection nonsense).

I’d imagine it’s debatable whether elderly grandparents past reproductive years are helping their grandchildren be more reproductively successful. Possible, but not a forgone conclusion by any means.

Actually this has been studied, establishing for instance the grandmother effect in pre-industrial Canada [0] ("women with mothers nearby had more and healthier children"). See [1] for more resources.

Anecdotally, I can personally attest that having grandparents too far to help makes it a lot harder to raise our two young children - there will certainly not be a third one.

[0] https://www.cbc.ca/news/canada/montreal/grandmother-effect-1...

[1] http://sacha-engelhardt.feedsrss.com/

Just to clarify, this would be a kin selection effect, not a group selection effect. It doesn’t have anything to do with elderly helping the “community” as the parent mentioned.

It’s an interesting hypothesis being studied, but not in any way cut or dry.

Grandmothers increase their offspring’s genetic impact, for daughters by increasing survival rates, for sons by increasing numbers of offspring.

http://en.wikipedia.org/wiki/Grandmother_hypothesis

> The grandmother hypothesis is a hypothesis to explain the existence of menopause in human life history by identifying the adaptive value of extended kin networking. It builds on the previously postulated "mother hypothesis" which states that as mothers age, the costs of reproducing become greater, and energy devoted to those activities would be better spent helping her offspring in their reproductive efforts. It suggests that by redirecting their energy onto those of their offspring, grandmothers can better ensure the survival of their genes through younger generations.

If the grandmother hypothesis is true, then you’re still talking kin selection effect via grandparents, which is very different than group selection. I concede that kin selection is very possible, but again, as this is an unproven hypothesis at the moment, still a matter of scientific debate, hence not really clear or obvious.

That's a hypothesis.

Again, reproduction is happening prior to any potential partner even knowing of a grandmother in many places in the animal kingdom. Even for humans actually.

So you're subscribing to the more adaptationalist line of reasoning for the existence of menopause. Which is fine. But you should concede that fact. Many others might subscribe to any of the other hypotheses for reproductive senescence. I subscribe to the artifactualist line of reasoning. ie - people just started living too long, and our bodies adapted for a 20-40 year life span. But there are numerous other hypotheses out there, many of them every bit as plausible as my artifactualist hypothesis. I only subscribe to the artifactualist hypothesis because it is the hypothesis most in line with the theory of evolution.

How long is too long? A woman is fertile through age 40 (and useful to care for offspring for another 10-20 years), a man is fertile through age 80 (and a genetically fit male would have valuable sperm long after his fitness showed in his phenotype). Why would our bodies adapt for a 20-40 year life span?

Yes, interesting question. Some relevant research: https://www.earth.com/news/kids-benefit-grandmother-healthy/

Edit: and https://www.cam.ac.uk/research/news/the-importance-of-grandm...

Edit2: and https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.1600...

Upsetting to see the downvoting on HN for providing scientific valid information in regard to conjecture.

For more information on why group theory isn’t supported by the scientific community see the following:

https://en.m.wikipedia.org/wiki/Group_selection

https://en.m.wikipedia.org/wiki/Kin_selection

https://en.m.wikipedia.org/wiki/Evolutionarily_stable_strate...

I don't think you were downvoted for providing scientific valid information in regard to conjecture. My best guess is that you were downvoted for calling something nonsense without anything to back it up. Maybe using gentler language would have helped here.

I was just thinking about this the other day...

Given how high the birth death rate is (for the mother), and presumably older bodies are weaker, there should be some evolutionary pressure for the menopause - simply said, as the P(death at childbirth) rises above some threshold, it's more beneficial for the mother to not be able get pregnant (and potentially die) again but instead continue nursing her existing children.

No such pressure exists for men because men have no cost of having extra offspring.

Richard Dawkins presents interesting arguments for several of what appear to be counterintuitive evolutionary adaptations in The Selfish Gene, IIRC.

> To my naive understanding of evolution, it has little incentive to fix anything that breaks after reproduction age. So I would not expect evolution to catch on cancer ever.

We have high cancer rates for children as well.

Interesting. Do you have a cite for this?

To my naive understanding of evolution, it has little incentive to fix anything that breaks after reproduction age. So I would not expect evolution to catch on cancer ever.

What if there were artificial evolutionary pressure? What if researchers start identifying specific mutations which are associated with cancer, then start editing them out of the DNA of unborn children?

What is "reproduction age"?

As I understand it, humans are quite unique in having menopause. Most species keep reproducing until they die, as do human males.

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