The Permian/Triassic mass extinction seems to have been the turning point. The creatures that have not changed much since that earlier time are the creatures that don't age. But when life revived at the end of the Triassic, the world was more competitive, eco-systems were more integrated, and specialization became more common. Aging allows specialization, we can see that most obviously with birds, which need to maintain a specific weight and body mass and ratio of wing span to body mass. A bird that simply grew and grew and grew, like a tortoise, would have a changing ratio of wingspan to body mass and therefore it would soon lose its ability to fly. The creatures that age are those that have a fixed adult body shape. By contrast, the tortoises and reptiles and fish that live forever also seem to grow and grow and grow -- their body mass to external ratio changes over time, therefore they are less specialized.
Massive snakes like anacondas, reticulated pythons and such are partly arboreal when small. When bigger, they can't really climb or hide in trees. Same thing for giant monitors. Komodo dragons are arboreal when small, and live a different lifestyle once large. They're kind of like different species, inhabiting different ecological niches.
From what I recall, many were hunted to extinction by domestic cats, post 1850s. So maybe even the larger ones may have survived if there was no drastic disturbance.
It's the opposite. You don't have children when you die, and evolution occurs overwhelmingly due to genetic diversity rather than iteration. That is, mutations are not nearly as important as the number of parents with diverse code to recombine with. Excluding older individuals causes the gene pool to become more consistent, because mutations are easier to lose.
If iteration was important, sexual maturity would occur drastically younger in birds and mammals, and you'd have tons of offspring to maximize iteration. Reptiles are the ones that have tons of children.
In a competitive environment, success is a function of fitness over your competitors. The fitness of a population is a function of the speed of fixation of advantageous alleles, which itself is a function of the number of generations. Thus in competitive environments, selective pressure towards generational turnover is increased, which is accomplished by aging. The issue of genetic diversity is satisfied by the close relationship of parent-offspring diversity. There's no reason to keep prior generations around just for the sake of genetic diversity.
>If iteration was important, sexual maturity would occur drastically younger in birds and mammals, and you'd have tons of offspring to maximize iteration
There are always antagonist selective pressures, e.g. selective pressures towards longer childhoods and fewer offspring when parental investment requirements grow.
> There's no reason to keep prior generations around just for the sake of genetic diversity.
This assumes there is some sort of reasoning going on in natural selection. What would lead to mutations that promote aging being selection per se, when the effects of aging are only experienced after reproductive age? That's not ruling out that mutations that cause aging aren't selected for, but they should give some short-term advantage.
The short-term advantage to the group is in reduced energy requirements from slowing metabolism. Also the prior generation is made less attractive to the next generation thus promoting the faster turnover of generations.
“It sounds dramatic to say that they don’t age at all, but basically their likelihood of dying does not change with age once they’re past reproduction,” says Reinke."
In humans, kids are born well below the age when we see the worst effects of aging. The old do not play much of a role in natural selection. It seems likely that aging or lack of it is more of an accident, then.
Yes, but in a very controlled way, typically with a fixed number of total devisions. Understanding aging is a slow process, but as far as I know current thought is that it has a lot to do with that replacement slowing down for a variety of reasons. This slow down seems like it may somewhat be a tradeoff with cancer though. Cells that divide too robustly end up cancer, cells that sort of shutdown instead are known as senescent and seem to contribute to aging
This could also be a selection bias based on the nature of the selection events. Longer lived species for whatever reason (slower metabolism, ability to go dormant for long periods) may have had an edge for a period of time. Its important to not that there wasn't a sudden radiation based on these specific surviving species after these events either.
Not sure if aging is related to growing forever. Our ears never stop growing but they don't live forever :P
It's more likely that those animals descended from an ancestor that didn't 'age' in the conventional sense _and_ had slow, unrestricted growth. Those two traits are not necessarily related.
Not sure if I agree with the 'specialized' moniker. All creatures are specialized to their ecological niche. Humans are kind of an exception.
What may have been selected for is fast and adaptable organisms. Why bother with 'aging' if you can tolerate damage over time, in exchange for more efficient organisms in the short term? You only need to repair enough to ensure the organism will reproduce (and maybe help care for the offspring for a while).
Humans are actually pretty good in that aspect compared to many animals. Probably because it takes a while before we are able to reproduce.
I think slow aging/longevity are "hard". You need excellent repair mechanisms, and for nothing to go wrong for a very long time.
Random mutations can easily cause problems/chop some time off your lifespan.
The question is, do individuals within the species benefit from longer life spans? To what extant are age related problems contributors to the deaths of individuals within a species?
I would guess that a higher percentage of turtles at a reproductive age die of age related disease than reproductively mature rats.
I would guess that turtles are much better at withstanding the passage of time, because time is a much more significant killer of turtles.
Similarly, flying birds and bats tend to live longer than mammals of similar body mass, probably because predation is a less significant contributor to their mortality (and thus issues such as age, relatively more significant).
Primates may be an exception, but they're also rather good at avoiding predators.
I think the idea is that evolution finds "good enough" solutions. If you can stop growth and it has the side effect of putting a time limit on an individual organism's lifespan, that may be an acceptable tradeoff in terms of genetic propagation. While halting growth without aging may be even better there may not have been enough pressure given how many animals in the wild don't die of old age.
Not that I've ever heard this theory before. But logically it seems plausible.
Right, the question is why would stopping growth necessarily limit an organism's lifespan. I don't think that's a given.
If you don't age and can stop growing at optimum size, then that's potentially a huge evolutionary advantage. And since even “marginally better” can often be selected given enough pressure, it's hard to imagine why growing older is so prevalent.
Back in 1994 we purchased a box turtle at a Santa Clara pet shop. We still have it. It must have been fully grown then because I am pretty sure it hasn't changed in size at all. I don't think we have noticed any behavioral changes, either. Appetite seems the same. Still gets pissed off and bangs its shell against the terrarium glass when it's hungry. So that would be something like 27 years without noticeable change.
Anyway we're close to retiring and I suppose it will transition to my daughter eventually. Maybe it will outlive her too.
I found a box turtle once, in the middle of the street in Long Beach, CA, and despite all of the Internet advice not to mess with box turtles, I didn't want it to get run over, so I brought it inside, went to the vet, and ended up keeping her for a few years until the Army was supposed to send me to Hawaii, where you're not allowed to bring reptiles. So I gave her to a family at Fort Lawton that built a huge enclosure in their back yard, and they took her to another vet to try and get an age estimate, and they guessed she was at least 70 years old. She definitely did not behave in any obviously elder manner. Same as any other box turtle I've ever met.
Our box turtle in winter goes as long as several months w/o eating. In fact some years it hibernates from a few weeks to a couple of months. This is inside at room temperature. During the active months it usually wants to eat turtle food every 2 or 3 days, and it will not touch food unless it is hungry. Ah, so here I have to admit that I let it train me to add a little water to the dry food, and the turtle hates dirty food, so I just have to give it new food when it's hungry. It is always hungry for crickets, roaches, grubs, big grasshoppers, earthworms, big green hornworm caterpillars[1], etc., but those are a lot of trouble to maintain a constant supply.
The turtle's terrarium (a big aquarium tank) is parallel to my path to the office, so I also know it's hungry, aside from the banging, when it sees me coming and races me the length of the tank. Did I mention that it appears to differentiate between me and other people?
[1] A favorite story I like to retell (and Grandpa starts in with...) is when our daughter was oh 11ish and we had a bunch of her classmates over I liked to drop a big tomato hornworm into the turtle tank with the kids all gathered round. When the cabal got packed in tight and a bunch of eeewwws! started I knew that once again, it was nature, green in tooth and claw.
The article talks about the protective phenotypes hypothesis, which basically says that animals with physical or chemical traits that confer protection (e.g. armor, spines, shells, or venom) have slower aging and live longer (compared to other animals their size).
The thinking is that these protective mechanisms can reduce mortality rate (you're not getting eaten by others), so you're likely to live longer, which exerts pressure to age more slowly.
Biggest support for the protective phenotype hypothesis is in turtles.
Isn't the worry that a specie that doesn't die off will have the older generation consuming all the resources, reducing the chance at survival by the newer generation?
Also, how do these species with extremely long lifespan adapt to changing environment?
I've gotten interested lately in the world of Ray Peat. His big thing is energizing the metabolism, healthy thyroid, etc. The idea is to maintain the state that a child is in to prolong life and be healthy. Maximize energy rather than limit it.
Below is an example of a random insight:
> His article Cholesterol in Context states that aging “seems to be a state of cholesterol starvation.” In other words, the ability to make cholesterol diminishes as we age.
“It sounds dramatic to say that they don’t age at all, but basically their likelihood of dying does not change with age once they’re past reproduction,”
Correct me if I'm wrong, but shouldn't the criterion be that the probability of death is the same between 80-90, 90-100, and so on (for example) to say that humans stop aging after 80?
Saying that your chance of dying is 50% after 80 != saying it's the same consistently after 80?
I think the parent poster meant "annual chance of dying after 80" as in, for any year 80+, you have a 50% chance of dying that year: it doesn't go up each year, so you don't "age" in that sense.
But this is not true. The life expectancy for an 80 year-old Caucasian American woman is over 9 years. The life expectancy a 90 year-old Caucasian American woman is less than 5 years.
“The Gompertz–Makeham law states that the human death rate is the sum of an age-dependent component (the Gompertz function, named after Benjamin Gompertz), which increases exponentially with age and an age-independent component (the Makeham term, named after William Makeham). In a protected environment where external causes of death are rare (laboratory conditions, low mortality countries, etc.), the age-independent mortality component is often negligible. In this case the formula simplifies to a Gompertz law of mortality. In 1825, Benjamin Gompertz proposed an exponential increase in death rates with age.
The Gompertz–Makeham law of mortality describes the age dynamics of human mortality rather accurately in the age window from about 30 to 80 years of age.
You probably remembered the first part of the sentence following that:
“At more advanced ages, some studies have found that death rates increase more slowly – a phenomenon known as the late-life mortality deceleration – but more recent studies disagree.”
No, not exactly. Your chance of dying at year 80, per that table, is about 5% at 80, 15% at 90, and 30% at 100 (averaging for males and females). Not the same, and not 50.
I think the observation they're trying to convey is that your expected number of years remaining goes down by much less than one year per year at those ages. A 90-year-old can expect to live for another 4.5 years, but on their 91st birthday, the chart surprisingly predicts not 3.5 but 4.2 years remaining. The number of expected years left drops more than 0.95 years per year until age 20, 0.9 years per year until age 40, down to 0.8 at 60, 0.5 at 80, and 0.1 at 100.
To have an average of 4.5, you need people to die before and after the mark.
So a lot of people drop off between 91 and 92. But those who make it to 92 have about 4.2 years remaining.
If you have a population of 100 people and 50 of them will live less than 1 year, and 50 of them will live an average of 10 years, that's 5.5 years on average for the whole population. But if you check that same population one year later, you will have 50 people who all live 9 years on average. You've managed to increase the average by eliminating the bottom.
Same thing is happening here.
And it's probably similar to professional sports careers. The average NFL career is about 3 years. However, if you make to 3 years, your average career length is about 7 years.
We probably need more of a median or mode than a mean.
The set of people alive at age N has size Sn. Some of them die. Some survive and form a new set of people alive at age N+1 with size Sn+1. Sn+1 <= Sn.
If the expected number of remaining years at age N was Y, death removed all the people that actually lived only 1 year or less, so the expected number of remaining years for people of age N+1 must be greater than Y.
Life expectancy at birth is always lower than at any other age.
> When the high infant mortality rate is factored in (life expectancy at birth) inhabitants of the Roman Empire had a life expectancy at birth of about 22–33 years
> The 46-49% that survived to their mid-teens could, on average, expect to reach around 48–54
> If the expected number of remaining years at age N was Y, death removed all the people that actually lived only 1 year or less, so the expected number of remaining years for people of age N+1 must be greater than Y.
No, that is neither necessary nor true. It must be greater than Y-1, not Y. Your way would mean that the expected duration of a life was infinite.
> I think the observation they're trying to convey is that your expected number of years remaining goes down by much less than one year per year at those ages.
But this is a necessary fact about everything. The alternative would be that the expected complete lifespan of an 81-year-old would be less than the expected complete lifespan of an 80-year-old, and that forms a logical contradiction with the fact that, in order to achieve that longer lifespan, the 80-year-old must become an 81-year-old.
Well that happens because the ones who die get excluded from the calculation. So it doesn't drop off nearly as fast.
It's calculating P(death|age = N), not P(death|age <= N). Now luckily you can calculate the second one, by adding all values up to that age together.
I would argue the value you're looking for, "when you die", is different still: P(death|age <= N, current_age=M), where M is your current age. You know, taking into account that you didn't die from sudden infant death syndrome or measles, or you wouldn't be here, but leaving everything in the future up to chance. To get that value, you should the odds of dying at all ages up to N, but only starting at your current age.
Aging is an advantage for species that have it. Reproductive fidelity is at its highest just after puberty in our species and probably most others. Turtle reproductive fidelity also declines with age (1). Having organisms become frail and die off in the years after puberty helps to maintain higher levels of reproductive fidelity among the population.
Related: Andrew Steele, a friend of mine whom I know from school, wrote a book about ageing, titled "Ageless", that was published late last year, It's a good read - highly recommended: https://andrewsteele.co.uk/ageless/
Essentially, a brief summary of the book is that research is ongoing, there is some hope, but do not expect any treatment in the very near future, meanwhile eat healthy and exercise. Overall, it is a very good book for understanding the process of aging. Delves into scientific evidence and provides good description of the most recent developments. However, do not expect it to give you any valuable practical advice apart from you already probably know: you need eat healthy, do not smoke, exercise etc.
"Death is very likely the single best invention of life. It is Life’s change agent. It clears out the old to make way for the new. Right now the new is you, but someday not too long from now, you will gradually become the old and be cleared away. Sorry to be so dramatic, but it is quite true.
Your time is limited, so don’t waste it living someone else’s life. Don’t be trapped by dogma — which is living with the results of other people’s thinking. Don’t let the noise of others’ opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition. They somehow already know what you truly want to become. Everything else is secondary"
I think this greatly diminishes the material benefits of experience and wisdom and over zealously glorifies youth for no obvious reason. Then it goes on to tell you to be super selfish and maximize your personal goals. I think as a society we would be well served by having as many of the aged in optimal health and living as long as possible.
This is one of the most important and mostly actively ignored facts that I know of. It is a uncomfortable truth regarding it as an individual but it is the only good solution for humanity as a whole.
People (mostly) don't change - they (have to) die for change to happen. I'm considering myself to be modern - today. In 70 years I'm quite sure I will no longer be by a large margin and I highly doubt that I'll be able to adapt my thinking incorporating them - just as I observe my parents and their peers not to be fully able to do so. As humanity with this we have a pool of new approaches (young) and tons of experience (older) which maximizes the likelyhood of finding the right approach to new challenges & making us survive as a species
>People (mostly) don't change - they (have to) die for change to happen.
An excellent justification for the forced retirement at 65 years of faculty in universities in East Asia. The sclerotic atmosphere in most US research universities, where over-privileged professors often linger into their 80s, has in my lifetime led to a growing intellectual stagnation in many (most? all?) academic fields.
If you lived a thousand years, you would have a thousand years to adapt. And if everybody lived a thousand years, society would adapt because geriatrics wouldn't conveniently drop dead in a few years but instead form the largest chunk of the market and stick around shaking their fists at people who think smart phones are a good UI for the retired.
The causality here seems unobvious. Is aging a necessity because we inherently lack the ability to change? Or do we become inflexible because we age?
Measures of willingness to change your mind and ability to learn new concepts is correlated with age. It seems just as reasonable to argue that if we could solve aging, we'd solve stagnation.
I think it's just a roll of the dice with age as a side effect.
Evolution's primary mechanism is to promote traits that increase the likelihood that you'll survive until you can reproduce. Perhaps multiple times. And for some species an additional period to raise the new generation.
So if evolution selects for a hard protective shell, this increases the odds that you reach reproductive age, which is the goal. This may accidentally also add an additional 100 years of lifespan. Which does nothing for reproduction, but it just happens anyway.
Yeah, the lack of connection to reproduction is why I'm skeptical of aging being an evolutionary mechanism. The above quote (appears to be from Steve Jobs) seems like an application of old ideas about the natural order to our current understanding.
I disagree. If we would not age and stay 25 years old until we have an accident, we could have hundreds of children each, which would drastically increase reproduction and should therefore be preferred by evolutionary selection.
Today, you may be right, but historically you're wrong.
Take any period in human history before 10,000 years ago and you'd find that nothing ever happened. As old person, the world would look exactly the same as when you were young. Even in modern times, there's centuries with no progress at all.
In multiple locales (Japan and the Caribbean) people have tried to sell me on eating turtle meat because it 'makes you strong'. Like there's this virility transfer that happens or something between you and the meat you consume. I only tried it once in Japan and it tasted like a pond, will never do that again. I definitely appreciate how they're pretty cool animals in general. I hope people get it out of their heads that eating them is like natural viagra or whatever.
Oh wait, I did try a turtle egg at a bar one time in a shot of chili guaro... Don't bite them open, there's sand inside.
People have been eating soft shell and snapping turtles in the SE US since... always? I grew up in the Everglades in South Florida and caught and ate many soft shell turtles. Fried up, tastes like... chicken? It's pretty good. The bullfrogs we gigged then were quite good too, the farmed ones I've tried in recent decades, not so much.
At no point was there any reference to particular inherent qualities of turtle meat, that I recall.
I dunno I kind of class them in animals which are too close to humans somehow to be desirable to eat. Like they have personalities and long lives that just get interrupted by people deciding they'd make a great meal. A lot of species of turtles are threatened by invasive species like bullfrogs and habitat degradation as well.
I'm not a picky eater by any means but there's definitely some meats out there I see on the menu and don't order, octopus for example - They're too smart to be munching on.
I've encountered many soft shell turtles (if you fish with bait in South Florida you will catch turtles) and I would not classify them as close to humans. I think if this sort of determination were to get any social traction then pigs would be the first granted clemency. I don't see that happening, ever. (I have no opinion at all about your preferences, obvs.)
Probably geosmin[1]. Some people really dislike it, others don't seem to mind as much. I grew up eating catfish and crawfish so I don't mind my food tasting a little muddy or ditchy, but that's just me.
That's really fascinating, I'm a big fan of knowing exactly what the chemical signature of scents and tastes are. It sounds kind of like cilantro in that way where some people just feel it tastes like soap while others love it (myself in the 2nd camp), but in the end from what I understand it's a genetic thing.
That article actually mentions that he's blind from cataracts and has lost his sense of smell. Clearly, some aging has taken place ... he would be unable to survive in the wild now.
The Permian/Triassic mass extinction seems to have been the turning point. The creatures that have not changed much since that earlier time are the creatures that don't age. But when life revived at the end of the Triassic, the world was more competitive, eco-systems were more integrated, and specialization became more common. Aging allows specialization, we can see that most obviously with birds, which need to maintain a specific weight and body mass and ratio of wing span to body mass. A bird that simply grew and grew and grew, like a tortoise, would have a changing ratio of wingspan to body mass and therefore it would soon lose its ability to fly. The creatures that age are those that have a fixed adult body shape. By contrast, the tortoises and reptiles and fish that live forever also seem to grow and grow and grow -- their body mass to external ratio changes over time, therefore they are less specialized.
This kind of happens to slow aging reptiles too.
Massive snakes like anacondas, reticulated pythons and such are partly arboreal when small. When bigger, they can't really climb or hide in trees. Same thing for giant monitors. Komodo dragons are arboreal when small, and live a different lifestyle once large. They're kind of like different species, inhabiting different ecological niches.
I wonder how some snakes' ability to atrophy and regenerate internal organs (including the heart) is related to aging: https://www.tacc.utexas.edu/-/how-pythons-regenerate-their-o...
That’s much closer to recovery from hibernation than an anti aging effect.
They might be the same for some animals.
That’s very interesting. Literally the dawn of aging. I’m skeptical though, do you have any sources you can point me to?
New Zealand has birds that don't fly due to the lack of predators and they don't get enormous and live very long life, IIRC.
Although the ones that were big got extinct so maybe you have a point...
From what I recall, many were hunted to extinction by domestic cats, post 1850s. So maybe even the larger ones may have survived if there was no drastic disturbance.
Several hunted to extinction by humans.
None of this was mentioned in the article. Where to read more about this point of view?
So you're saying that aging is basically growth control?
if you were optimizing for success for a whole species, do you see how going for fast iterations and throwing out old code could appear as a strategy?
It's the opposite. You don't have children when you die, and evolution occurs overwhelmingly due to genetic diversity rather than iteration. That is, mutations are not nearly as important as the number of parents with diverse code to recombine with. Excluding older individuals causes the gene pool to become more consistent, because mutations are easier to lose.
If iteration was important, sexual maturity would occur drastically younger in birds and mammals, and you'd have tons of offspring to maximize iteration. Reptiles are the ones that have tons of children.
In a competitive environment, success is a function of fitness over your competitors. The fitness of a population is a function of the speed of fixation of advantageous alleles, which itself is a function of the number of generations. Thus in competitive environments, selective pressure towards generational turnover is increased, which is accomplished by aging. The issue of genetic diversity is satisfied by the close relationship of parent-offspring diversity. There's no reason to keep prior generations around just for the sake of genetic diversity.
>If iteration was important, sexual maturity would occur drastically younger in birds and mammals, and you'd have tons of offspring to maximize iteration
There are always antagonist selective pressures, e.g. selective pressures towards longer childhoods and fewer offspring when parental investment requirements grow.
> There's no reason to keep prior generations around just for the sake of genetic diversity.
This assumes there is some sort of reasoning going on in natural selection. What would lead to mutations that promote aging being selection per se, when the effects of aging are only experienced after reproductive age? That's not ruling out that mutations that cause aging aren't selected for, but they should give some short-term advantage.
The short-term advantage to the group is in reduced energy requirements from slowing metabolism. Also the prior generation is made less attractive to the next generation thus promoting the faster turnover of generations.
The article states:
“It sounds dramatic to say that they don’t age at all, but basically their likelihood of dying does not change with age once they’re past reproduction,” says Reinke."
In humans, kids are born well below the age when we see the worst effects of aging. The old do not play much of a role in natural selection. It seems likely that aging or lack of it is more of an accident, then.
Growing means you're making new cell, aging is when you're cell seems tired and stop regenerating or being eaten by other cells.
Aren't cells replaced periodically?
Yes, but in a very controlled way, typically with a fixed number of total devisions. Understanding aging is a slow process, but as far as I know current thought is that it has a lot to do with that replacement slowing down for a variety of reasons. This slow down seems like it may somewhat be a tradeoff with cancer though. Cells that divide too robustly end up cancer, cells that sort of shutdown instead are known as senescent and seem to contribute to aging
This could also be a selection bias based on the nature of the selection events. Longer lived species for whatever reason (slower metabolism, ability to go dormant for long periods) may have had an edge for a period of time. Its important to not that there wasn't a sudden radiation based on these specific surviving species after these events either.
Not sure if aging is related to growing forever. Our ears never stop growing but they don't live forever :P
It's more likely that those animals descended from an ancestor that didn't 'age' in the conventional sense _and_ had slow, unrestricted growth. Those two traits are not necessarily related.
Not sure if I agree with the 'specialized' moniker. All creatures are specialized to their ecological niche. Humans are kind of an exception.
What may have been selected for is fast and adaptable organisms. Why bother with 'aging' if you can tolerate damage over time, in exchange for more efficient organisms in the short term? You only need to repair enough to ensure the organism will reproduce (and maybe help care for the offspring for a while).
Humans are actually pretty good in that aspect compared to many animals. Probably because it takes a while before we are able to reproduce.
I think slow aging/longevity are "hard". You need excellent repair mechanisms, and for nothing to go wrong for a very long time.
Random mutations can easily cause problems/chop some time off your lifespan.
The question is, do individuals within the species benefit from longer life spans? To what extant are age related problems contributors to the deaths of individuals within a species?
I would guess that a higher percentage of turtles at a reproductive age die of age related disease than reproductively mature rats. I would guess that turtles are much better at withstanding the passage of time, because time is a much more significant killer of turtles.
Similarly, flying birds and bats tend to live longer than mammals of similar body mass, probably because predation is a less significant contributor to their mortality (and thus issues such as age, relatively more significant). Primates may be an exception, but they're also rather good at avoiding predators.
[citation needed]
It’s an interesting hypothesis, but why can’t growth slow or stall?
I think the idea is that evolution finds "good enough" solutions. If you can stop growth and it has the side effect of putting a time limit on an individual organism's lifespan, that may be an acceptable tradeoff in terms of genetic propagation. While halting growth without aging may be even better there may not have been enough pressure given how many animals in the wild don't die of old age.
Not that I've ever heard this theory before. But logically it seems plausible.
Right, the question is why would stopping growth necessarily limit an organism's lifespan. I don't think that's a given.
If you don't age and can stop growing at optimum size, then that's potentially a huge evolutionary advantage. And since even “marginally better” can often be selected given enough pressure, it's hard to imagine why growing older is so prevalent.
What are you talking about - I've been growing and growing as an adult!
Back in 1994 we purchased a box turtle at a Santa Clara pet shop. We still have it. It must have been fully grown then because I am pretty sure it hasn't changed in size at all. I don't think we have noticed any behavioral changes, either. Appetite seems the same. Still gets pissed off and bangs its shell against the terrarium glass when it's hungry. So that would be something like 27 years without noticeable change.
Anyway we're close to retiring and I suppose it will transition to my daughter eventually. Maybe it will outlive her too.
I found a box turtle once, in the middle of the street in Long Beach, CA, and despite all of the Internet advice not to mess with box turtles, I didn't want it to get run over, so I brought it inside, went to the vet, and ended up keeping her for a few years until the Army was supposed to send me to Hawaii, where you're not allowed to bring reptiles. So I gave her to a family at Fort Lawton that built a huge enclosure in their back yard, and they took her to another vet to try and get an age estimate, and they guessed she was at least 70 years old. She definitely did not behave in any obviously elder manner. Same as any other box turtle I've ever met.
Sounds like the beginning of a clan dedicated to serving a totem beast.
I have resisted naming our turtle 'Om'.
Resistance won’t be needed if you name it 'Ohm'.
Pratchett?
Small Gods
The idea that a turtle gets pissed off and starts banging the glass made me laugh. Feed your turtle!
Our box turtle in winter goes as long as several months w/o eating. In fact some years it hibernates from a few weeks to a couple of months. This is inside at room temperature. During the active months it usually wants to eat turtle food every 2 or 3 days, and it will not touch food unless it is hungry. Ah, so here I have to admit that I let it train me to add a little water to the dry food, and the turtle hates dirty food, so I just have to give it new food when it's hungry. It is always hungry for crickets, roaches, grubs, big grasshoppers, earthworms, big green hornworm caterpillars[1], etc., but those are a lot of trouble to maintain a constant supply.
The turtle's terrarium (a big aquarium tank) is parallel to my path to the office, so I also know it's hungry, aside from the banging, when it sees me coming and races me the length of the tank. Did I mention that it appears to differentiate between me and other people?
[1] A favorite story I like to retell (and Grandpa starts in with...) is when our daughter was oh 11ish and we had a bunch of her classmates over I liked to drop a big tomato hornworm into the turtle tank with the kids all gathered round. When the cabal got packed in tight and a bunch of eeewwws! started I knew that once again, it was nature, green in tooth and claw.
We have a turtle that was found somewhere around 30 years ago, so full age largely unknown, but... like old.
The article talks about the protective phenotypes hypothesis, which basically says that animals with physical or chemical traits that confer protection (e.g. armor, spines, shells, or venom) have slower aging and live longer (compared to other animals their size).
The thinking is that these protective mechanisms can reduce mortality rate (you're not getting eaten by others), so you're likely to live longer, which exerts pressure to age more slowly.
Biggest support for the protective phenotype hypothesis is in turtles.
And these protections probably take more resources to produce, making it less advantageous to create offspring and die off.
Isn't the worry that a specie that doesn't die off will have the older generation consuming all the resources, reducing the chance at survival by the newer generation?
Also, how do these species with extremely long lifespan adapt to changing environment?
The turtles don't seem to be worried about it.
Rumor has it Peter Thiel is already pumping turtle blood into his veins.
Fake news.
Reptiles do not need another reptile's blood
It's been confirmed, and an NFT of prehistoric turtle blood is on the blockchain.
And Tom Cruise already sampled it.
I've gotten interested lately in the world of Ray Peat. His big thing is energizing the metabolism, healthy thyroid, etc. The idea is to maintain the state that a child is in to prolong life and be healthy. Maximize energy rather than limit it.
Below is an example of a random insight:
> His article Cholesterol in Context states that aging “seems to be a state of cholesterol starvation.” In other words, the ability to make cholesterol diminishes as we age.
https://www.womensinternational.com/blog/aging-is-cholestero...
It's tough to synthesize his thought though. Whoever does and sells a popular level book of it will make a lot of money.
“It sounds dramatic to say that they don’t age at all, but basically their likelihood of dying does not change with age once they’re past reproduction,”
Same with humans, to a degree. Actuarials place your chance of dying at 50% after the age of 80. So we 'stop aging' after 80!
This is not true. Either that it’s 50% at 80 or that it is flat after 80. Here’s an actuarial table: https://www.ssa.gov/oact/STATS/table4c6.html
Annual chance of dying is 5% at 80 and continues rising every year (9% by 85, 16% by 90, 25% by 95, 35% by 100).
I see that! The chart I recall is clearly very out of date. Thanks!
Correct me if I'm wrong, but shouldn't the criterion be that the probability of death is the same between 80-90, 90-100, and so on (for example) to say that humans stop aging after 80?
Saying that your chance of dying is 50% after 80 != saying it's the same consistently after 80?
I think the parent poster meant "annual chance of dying after 80" as in, for any year 80+, you have a 50% chance of dying that year: it doesn't go up each year, so you don't "age" in that sense.
But this is not true. The life expectancy for an 80 year-old Caucasian American woman is over 9 years. The life expectancy a 90 year-old Caucasian American woman is less than 5 years.
Yes the coin of death remembers how lucky you were in your eighties and skews towards tails in your 90s. Still 50/50 as its a coin.
There’s only two possibilities: I’ll either win the lottery or I won’t, so it’s a 50/50 shot!
I guess I am a bayesian :)
https://en.wikipedia.org/wiki/Gompertz–Makeham_law_of_mortal...:
“The Gompertz–Makeham law states that the human death rate is the sum of an age-dependent component (the Gompertz function, named after Benjamin Gompertz), which increases exponentially with age and an age-independent component (the Makeham term, named after William Makeham). In a protected environment where external causes of death are rare (laboratory conditions, low mortality countries, etc.), the age-independent mortality component is often negligible. In this case the formula simplifies to a Gompertz law of mortality. In 1825, Benjamin Gompertz proposed an exponential increase in death rates with age.
The Gompertz–Makeham law of mortality describes the age dynamics of human mortality rather accurately in the age window from about 30 to 80 years of age.
You probably remembered the first part of the sentence following that:
“At more advanced ages, some studies have found that death rates increase more slowly – a phenomenon known as the late-life mortality deceleration – but more recent studies disagree.”
Even if that were true (something wikipedia contests. See also https://en.wikipedia.org/wiki/Late-life_mortality_decelerati...), that doesn’t mean rate of death decreases, just that it increases slower than this model predicts.
71569457046263802294811533723186532165584657342365752577109445058227039255480148842668944867280814080000000000000000000 is a good age to stop aging.
Sorry, couldn't miss a factorial joke.
You could witness https://czep.net/weblog/52cards.html 3748508088259971967302999598973478215811072000000 times until then. Frankly, I'm terrified.
Does this actuarial table support your claim that chance of dying is stable at 50% after 80: https://www.ssa.gov/oact/STATS/table4c6.html
No, not exactly. Your chance of dying at year 80, per that table, is about 5% at 80, 15% at 90, and 30% at 100 (averaging for males and females). Not the same, and not 50.
I think the observation they're trying to convey is that your expected number of years remaining goes down by much less than one year per year at those ages. A 90-year-old can expect to live for another 4.5 years, but on their 91st birthday, the chart surprisingly predicts not 3.5 but 4.2 years remaining. The number of expected years left drops more than 0.95 years per year until age 20, 0.9 years per year until age 40, down to 0.8 at 60, 0.5 at 80, and 0.1 at 100.
Quirks of statistics.
To have an average of 4.5, you need people to die before and after the mark.
So a lot of people drop off between 91 and 92. But those who make it to 92 have about 4.2 years remaining.
If you have a population of 100 people and 50 of them will live less than 1 year, and 50 of them will live an average of 10 years, that's 5.5 years on average for the whole population. But if you check that same population one year later, you will have 50 people who all live 9 years on average. You've managed to increase the average by eliminating the bottom.
Same thing is happening here.
And it's probably similar to professional sports careers. The average NFL career is about 3 years. However, if you make to 3 years, your average career length is about 7 years.
We probably need more of a median or mode than a mean.
The prediction is not surprising.
The set of people alive at age N has size Sn. Some of them die. Some survive and form a new set of people alive at age N+1 with size Sn+1. Sn+1 <= Sn.
If the expected number of remaining years at age N was Y, death removed all the people that actually lived only 1 year or less, so the expected number of remaining years for people of age N+1 must be greater than Y.
Life expectancy at birth is always lower than at any other age.
Check https://en.wikipedia.org/wiki/Demography_of_the_Roman_Empire
> When the high infant mortality rate is factored in (life expectancy at birth) inhabitants of the Roman Empire had a life expectancy at birth of about 22–33 years
> The 46-49% that survived to their mid-teens could, on average, expect to reach around 48–54
> If the expected number of remaining years at age N was Y, death removed all the people that actually lived only 1 year or less, so the expected number of remaining years for people of age N+1 must be greater than Y.
No, that is neither necessary nor true. It must be greater than Y-1, not Y. Your way would mean that the expected duration of a life was infinite.
> I think the observation they're trying to convey is that your expected number of years remaining goes down by much less than one year per year at those ages.
But this is a necessary fact about everything. The alternative would be that the expected complete lifespan of an 81-year-old would be less than the expected complete lifespan of an 80-year-old, and that forms a logical contradiction with the fact that, in order to achieve that longer lifespan, the 80-year-old must become an 81-year-old.
I love how, even for men, life expectancy doesn't fall below one year until age 113.
Well that happens because the ones who die get excluded from the calculation. So it doesn't drop off nearly as fast.
It's calculating P(death|age = N), not P(death|age <= N). Now luckily you can calculate the second one, by adding all values up to that age together.
I would argue the value you're looking for, "when you die", is different still: P(death|age <= N, current_age=M), where M is your current age. You know, taking into account that you didn't die from sudden infant death syndrome or measles, or you wouldn't be here, but leaving everything in the future up to chance. To get that value, you should the odds of dying at all ages up to N, but only starting at your current age.
Wasn't this result largely cause by small sample size?
to the downvoters: https://www.science.org/content/article/once-you-hit-age-agi...
At a certain point, humans appear to stop aging. Just it is at 105, not 80 :)
But if you flip a coin every year the chances of getting heads after 10 rolls is quite high.
Yup, it is then still quite high - exactly 50%.
I'm sure he meant within 10 years. So (1-(0.5¹⁰))=99.9% chance
(that is, chance of flipping tails 10 times in a row is 0.5¹⁰ - chance of any head is what's left)
Aging is an advantage for species that have it. Reproductive fidelity is at its highest just after puberty in our species and probably most others. Turtle reproductive fidelity also declines with age (1). Having organisms become frail and die off in the years after puberty helps to maintain higher levels of reproductive fidelity among the population.
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4988574/
Related: Andrew Steele, a friend of mine whom I know from school, wrote a book about ageing, titled "Ageless", that was published late last year, It's a good read - highly recommended: https://andrewsteele.co.uk/ageless/
Worth following on Twitter if you're into the topic: https://twitter.com/statto
From the top Amazon review:
Essentially, a brief summary of the book is that research is ongoing, there is some hope, but do not expect any treatment in the very near future, meanwhile eat healthy and exercise. Overall, it is a very good book for understanding the process of aging. Delves into scientific evidence and provides good description of the most recent developments. However, do not expect it to give you any valuable practical advice apart from you already probably know: you need eat healthy, do not smoke, exercise etc.
It’s very interesting to know how they get protected against tumors at such an old age.
"Death is very likely the single best invention of life. It is Life’s change agent. It clears out the old to make way for the new. Right now the new is you, but someday not too long from now, you will gradually become the old and be cleared away. Sorry to be so dramatic, but it is quite true.
Your time is limited, so don’t waste it living someone else’s life. Don’t be trapped by dogma — which is living with the results of other people’s thinking. Don’t let the noise of others’ opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition. They somehow already know what you truly want to become. Everything else is secondary"
I think this greatly diminishes the material benefits of experience and wisdom and over zealously glorifies youth for no obvious reason. Then it goes on to tell you to be super selfish and maximize your personal goals. I think as a society we would be well served by having as many of the aged in optimal health and living as long as possible.
This is one of the most important and mostly actively ignored facts that I know of. It is a uncomfortable truth regarding it as an individual but it is the only good solution for humanity as a whole.
People (mostly) don't change - they (have to) die for change to happen. I'm considering myself to be modern - today. In 70 years I'm quite sure I will no longer be by a large margin and I highly doubt that I'll be able to adapt my thinking incorporating them - just as I observe my parents and their peers not to be fully able to do so. As humanity with this we have a pool of new approaches (young) and tons of experience (older) which maximizes the likelyhood of finding the right approach to new challenges & making us survive as a species
>People (mostly) don't change - they (have to) die for change to happen.
An excellent justification for the forced retirement at 65 years of faculty in universities in East Asia. The sclerotic atmosphere in most US research universities, where over-privileged professors often linger into their 80s, has in my lifetime led to a growing intellectual stagnation in many (most? all?) academic fields.
If you lived a thousand years, you would have a thousand years to adapt. And if everybody lived a thousand years, society would adapt because geriatrics wouldn't conveniently drop dead in a few years but instead form the largest chunk of the market and stick around shaking their fists at people who think smart phones are a good UI for the retired.
The causality here seems unobvious. Is aging a necessity because we inherently lack the ability to change? Or do we become inflexible because we age?
Measures of willingness to change your mind and ability to learn new concepts is correlated with age. It seems just as reasonable to argue that if we could solve aging, we'd solve stagnation.
I think it's just a roll of the dice with age as a side effect.
Evolution's primary mechanism is to promote traits that increase the likelihood that you'll survive until you can reproduce. Perhaps multiple times. And for some species an additional period to raise the new generation.
So if evolution selects for a hard protective shell, this increases the odds that you reach reproductive age, which is the goal. This may accidentally also add an additional 100 years of lifespan. Which does nothing for reproduction, but it just happens anyway.
Yeah, the lack of connection to reproduction is why I'm skeptical of aging being an evolutionary mechanism. The above quote (appears to be from Steve Jobs) seems like an application of old ideas about the natural order to our current understanding.
I think Jobs' comments are indeed to be seen within the human cultural context only. Culture being a fancy word for stuff we made up.
Quite a few examples in nature where species drop dead directly after mating.
I disagree. If we would not age and stay 25 years old until we have an accident, we could have hundreds of children each, which would drastically increase reproduction and should therefore be preferred by evolutionary selection.
Today, you may be right, but historically you're wrong.
Take any period in human history before 10,000 years ago and you'd find that nothing ever happened. As old person, the world would look exactly the same as when you were young. Even in modern times, there's centuries with no progress at all.
> People (mostly) don't change - they (have to) die for change to happen.
How much of that is a consequence of the fact that our brains physiologically lose the ability to change over time though?
Life is deaths greatest invention.
Essence Of Wild Turtle soon to appear in a pharmacy near you.
Already part of Traditional Chinese Medicine (ex https://en.m.wikipedia.org/wiki/Guilinggao)
Planaria essentially have immortal bodies, excepting being destroyed by environmental forces.
Microscopic Hydra are even more impressive you can blend them to a pulp and they'll just grow into more copies of Hydra animals.
In multiple locales (Japan and the Caribbean) people have tried to sell me on eating turtle meat because it 'makes you strong'. Like there's this virility transfer that happens or something between you and the meat you consume. I only tried it once in Japan and it tasted like a pond, will never do that again. I definitely appreciate how they're pretty cool animals in general. I hope people get it out of their heads that eating them is like natural viagra or whatever.
Oh wait, I did try a turtle egg at a bar one time in a shot of chili guaro... Don't bite them open, there's sand inside.
People have been eating soft shell and snapping turtles in the SE US since... always? I grew up in the Everglades in South Florida and caught and ate many soft shell turtles. Fried up, tastes like... chicken? It's pretty good. The bullfrogs we gigged then were quite good too, the farmed ones I've tried in recent decades, not so much.
At no point was there any reference to particular inherent qualities of turtle meat, that I recall.
I dunno I kind of class them in animals which are too close to humans somehow to be desirable to eat. Like they have personalities and long lives that just get interrupted by people deciding they'd make a great meal. A lot of species of turtles are threatened by invasive species like bullfrogs and habitat degradation as well.
I'm not a picky eater by any means but there's definitely some meats out there I see on the menu and don't order, octopus for example - They're too smart to be munching on.
I've encountered many soft shell turtles (if you fish with bait in South Florida you will catch turtles) and I would not classify them as close to humans. I think if this sort of determination were to get any social traction then pigs would be the first granted clemency. I don't see that happening, ever. (I have no opinion at all about your preferences, obvs.)
Yeah I guess we all anthropomorphize our favorite creatures
>I kind of class them in animals which are too close to humans somehow to be desirable to eat.
That is certainly the first time I have heard this said about turtles.
Pigs and cows seem pretty smart to me. Smarter than horses, at least.
edit: hell, birds are pretty smart, too, even if domestic chickens seem exceptionally stupid.
> it tasted like a pond
Probably geosmin[1]. Some people really dislike it, others don't seem to mind as much. I grew up eating catfish and crawfish so I don't mind my food tasting a little muddy or ditchy, but that's just me.
[1]: https://en.wikipedia.org/wiki/Geosmin
That's really fascinating, I'm a big fan of knowing exactly what the chemical signature of scents and tastes are. It sounds kind of like cilantro in that way where some people just feel it tastes like soap while others love it (myself in the 2nd camp), but in the end from what I understand it's a genetic thing.
I like turtles!
and we really have no idea how to transfer that to humans...and we won't for a long long long time
If this is true, why is the oldest one only trivially older than the oldest human?
Oldest known turtle you mean? [1]
I wouldn't call 190 years old "trivially older".
[1] https://en.wikipedia.org/wiki/Jonathan_%28tortoise%29
That article actually mentions that he's blind from cataracts and has lost his sense of smell. Clearly, some aging has taken place ... he would be unable to survive in the wild now.
Lucky bastards.
Aging is def a feature of evolution.