Their is a saying among scientists that the more you know about the scientific subject a journalist is writing about, the less of what he writes makes any sense. There is a long new article in the New York Times magazine about a hydrozoan jellyfish, Turritopsis dohrnii, which the author claims holds the key to immortality. As someone who happens to work on hydrozoans, and on aging, I can assure you that not a bit of it makes any sense. The title, "Can a Jellyfish Unlock the Secret of
Immortality?" should be a dead giveaway that this is magical thinking
with a whitewash of pseudoscience. The argument behind the article, striped of its misunderstandings and untruths, goes something like this:
1. There is this jellyfish that can develop back from the medusa phase, which we normally think of as the adult, to the polpy phase, which we normally think of as the juvenile. It can then develop into the medusa phase again.
2. We are going to assume that this is the only know case of an organism that does not show a human-like pattern of aging.
3. We are going to assume that this non-human like pattern is equivalent to immortality.
4. We are going to assume that if we understood the mechanisms behind this assumed immortality, we would know how to make humans immortal.
5. We would know by now what makes them immortal except that we are going to assume that the one researcher I talked to extensively for the article who studies the species is the only one doing so.
6. We are going to assume that this one researcher is unfunded and working alone not because he is considered a crackpot, but because the rest of science is just too blind and lazy to see the importance of this man and his work.
7. We are going to assume that when he has learned a little bit more, we will achieve immortality.
I do not recommend that you read it, and mention it only because I have been asked about it, and because I would like to speak briefly about the word immortality. Immortality is defined as immunity from death. Immortal beings cannot be killed. Turritopsis dohrnii can very easily be killed. Put one out of water for a few minutes, feed it to a predatory snail, heat it, freeze it, slice, dice or frappe it, and it will be dead. Ergo not immortal. However the journalists are not to blame for the misuse of the word. A very good recent paper in PNAS from a very good careful research group is titled, "FoxO is a critical regulator of stem cell maintenance in immortal Hydra." They use the word immortal as many people in bio-gerontology do, to mean that the risk of death does not increase with age. My general impression is that using the word in this way is misleading, but that it is a lot flashier than 'nonsenescing' and therefore widely used.
Showing posts with label aging. Show all posts
Showing posts with label aging. Show all posts
Wednesday, November 28, 2012
Saturday, February 11, 2012
Emissions of the aged
Projections of future carbon-dioxide emissions are complicated. How will energy consumption habits change as societies get richer or more urban? What mix of sources will we be getting our energy from?
My friend and colleague Emilo Zagheni decided we should make the calculus that much more complicated (and informative) by also asking how the aging of the population will influence carbon outputs. A demographer's demographer, which Emilio surely is, is never happy with any calculation that does not include age-structure in one way or another.
This article in the Economist summarizes what he did and what he found. As people get older, they tend to consume more and more, emitting more and more carbon, until 65ish, at which point consumption tends to start declining. See the graph, and the analysis, in the Economist, or the original in the journal Demography (2011) pp 371-399. The punchline for the carbon-watcher is that the changing age-structure will tend to increase carbon emissions until about 2050, after which point such a large portion of the population will be above 65 (I'll be 73) that the age effect will begin to marginally decrease emissions.
I should finish with a quote from Ron Lee, Professor of both Demography and Economics at UC Berkeley, who both Emilio and I studied under. Ron was one of the inventors of the widely used Lee-Carter method* (1992) for forecasting future mortality patterns. Seventeen years later, I asked Ron how well his forecasts for the first 17 years matched what had actually happened in those years. He cocked his head slightly to the left, sighed sagely and said, "Well, demographers are well aware that our projections don't always fair so well in a complex world. But we console ourselves with the knowledge that we do much better than the economists."
* The original article has been cited more than 1000 times in the peer-reviewed literature, and modifications are used by the US Census Bureau, the UN, and so forth.
My friend and colleague Emilo Zagheni decided we should make the calculus that much more complicated (and informative) by also asking how the aging of the population will influence carbon outputs. A demographer's demographer, which Emilio surely is, is never happy with any calculation that does not include age-structure in one way or another.
This article in the Economist summarizes what he did and what he found. As people get older, they tend to consume more and more, emitting more and more carbon, until 65ish, at which point consumption tends to start declining. See the graph, and the analysis, in the Economist, or the original in the journal Demography (2011) pp 371-399. The punchline for the carbon-watcher is that the changing age-structure will tend to increase carbon emissions until about 2050, after which point such a large portion of the population will be above 65 (I'll be 73) that the age effect will begin to marginally decrease emissions.
I should finish with a quote from Ron Lee, Professor of both Demography and Economics at UC Berkeley, who both Emilio and I studied under. Ron was one of the inventors of the widely used Lee-Carter method* (1992) for forecasting future mortality patterns. Seventeen years later, I asked Ron how well his forecasts for the first 17 years matched what had actually happened in those years. He cocked his head slightly to the left, sighed sagely and said, "Well, demographers are well aware that our projections don't always fair so well in a complex world. But we console ourselves with the knowledge that we do much better than the economists."
* The original article has been cited more than 1000 times in the peer-reviewed literature, and modifications are used by the US Census Bureau, the UN, and so forth.
Wednesday, December 02, 2009
"Possible to live forever"
Iris came to the Institute to have lunch with me. We were sitting and eating the tasty pasta dish she'd made when my friend passed by. He stopped to say hi. Iris picked up on the fact that he was excited about something before I did.
"What's new?" she asked.
"I have discovered that it is possible to live forever," he said, with no hint of irony.
"Oh?," I said, taking another delicious bite of pasta and doing my best to maintain a neutral tone.
He went on to describe how he had noticed that under a set of mathematical assumptions about the pattern of human aging, if one plugs in the right values for various parameters, one can get the result that life expectancy approaches infinity. I'm not going to give away his secrets, or try to explain the bit of calculus he uses, but the whole proof fit on one page including only a handful of equations. There, in black and white was mathematical proof that one could live forever. Well sort of. The math was impeccable, at least I couldn't peck it. The question is how relevant was the mathematical model, and how meaningful were the limits he was taking?
Often when we use mathematical models of the world it is because we think they not only approximate the outcomes of the pattern, but actually describe something about the underlying process. An object fired up into the air will fall to earth in a parabola, a real, honest, no tricks involved parabola. The form arises just from the interplay of momentum and gravity, and the parabola arises, not as a fluke, but under a wide range of gravities and velocities. In other words, we think that sometimes the mathematical ideal is what the world is actually approximating. There is thinking that the mathematical forms my friend employs actually are the underlying form of human aging. They are our best guesses anyway. So maybe, just maybe, exploring the limits of that form tell us something about the limits of possibility when it comes to aging. Unfortunately, relationships that hold under a wide range of velocities often don't hold at the limits. Shoot the object at an improbably high velocity and it will escape Earth's gravity entirely, and likely end up orbiting the Sun, eventually making an ellipse. Shoot the object too slowly and forces such as viscosity, friction and wind become increasingly important, and the object will trace a good approximation of a line-segment to the ground. So while my friend's mathematical discovery is interesting and novel, I remain skeptical that he has found the possibility of immortality. Rather he has shown that if one makes extraordinary and unexpected assumptions, one can arrive at extraordinary and unexpected conclusions. Important, but hardly the key to eternal life.
Sorry to be such a downer.
"What's new?" she asked.
"I have discovered that it is possible to live forever," he said, with no hint of irony.
"Oh?," I said, taking another delicious bite of pasta and doing my best to maintain a neutral tone.
He went on to describe how he had noticed that under a set of mathematical assumptions about the pattern of human aging, if one plugs in the right values for various parameters, one can get the result that life expectancy approaches infinity. I'm not going to give away his secrets, or try to explain the bit of calculus he uses, but the whole proof fit on one page including only a handful of equations. There, in black and white was mathematical proof that one could live forever. Well sort of. The math was impeccable, at least I couldn't peck it. The question is how relevant was the mathematical model, and how meaningful were the limits he was taking?
Often when we use mathematical models of the world it is because we think they not only approximate the outcomes of the pattern, but actually describe something about the underlying process. An object fired up into the air will fall to earth in a parabola, a real, honest, no tricks involved parabola. The form arises just from the interplay of momentum and gravity, and the parabola arises, not as a fluke, but under a wide range of gravities and velocities. In other words, we think that sometimes the mathematical ideal is what the world is actually approximating. There is thinking that the mathematical forms my friend employs actually are the underlying form of human aging. They are our best guesses anyway. So maybe, just maybe, exploring the limits of that form tell us something about the limits of possibility when it comes to aging. Unfortunately, relationships that hold under a wide range of velocities often don't hold at the limits. Shoot the object at an improbably high velocity and it will escape Earth's gravity entirely, and likely end up orbiting the Sun, eventually making an ellipse. Shoot the object too slowly and forces such as viscosity, friction and wind become increasingly important, and the object will trace a good approximation of a line-segment to the ground. So while my friend's mathematical discovery is interesting and novel, I remain skeptical that he has found the possibility of immortality. Rather he has shown that if one makes extraordinary and unexpected assumptions, one can arrive at extraordinary and unexpected conclusions. Important, but hardly the key to eternal life.
Sorry to be such a downer.
Tuesday, November 10, 2009
More musings on individuality and Hydra
It was a trick question. I admit. Well not a trick exactly, but a question to which science does not have a right answer. Even when the question is defined fairly exactly, it isn't clear what unit we should be looking at.
I've already talked a little bit about the hyrda, but I want to give you more detail, because they are such an interesting and bizarre case. There are at least four levels at which we could define the individual in hydra. The smallest is the individual cell. Most cells in a hydra are capable of turning into any kind of hydra cell, producing a whole new hydra, and moving on their own. People have turned a whole hydra body inside out, and the cells that were on the outside just become inside digestive cells, and the cells that were on the outside become skin cells, and the community of cells goes on about its business. Second, the polyp, that thing with the tentacles and digestive system we classically think of as the individual animal. It looks like a little animal. It acts like a little animal (in most ways). It hunts, it reproduces itself, it has different cells doing different jobs. Third, there is the physically attached cluster of hydra. Through budding (growing a new hydra-shaped organism off the side of the old one) hydra reproduce asexually, but the buds get to be a fair portion of the size of the parent before separating, and are generally of almost full complexity while still physically and physiologically attached. One or two or occasionally more buds can be growing off the main polyp at the same time, and one could easily see this mass of genetically identical connected cells as one individual, despite the fact that it has multiple sets of tentacles feeding multiple digestive systems. Finally, one could consider that these genetically identical groups of cells remain part of the same individual even after physical separation. The genetic individual could after a short time encompass many thousands of polyps.
At which of these four levels does senescence occur? We know from experimental evidence that the risk of death by individual cells increases with age, so we have senescence in level one. In level two, the polyp, the experimental evidence points to no senescence, and the same goes for level three. At level four we don't have experimental evidence, but Mueller's Ratchet implies that there would be slow senescence of the genetic individual. Without going into details, Mueller's Ratchet is a line of genetic reasoning which makes clear that the number of harmful mutations in an asexually producing population almost always increases with time, where the number could decrease with sexual reproduction. So as the genetic individual of the hydra keeps producing more polyps, the newer polyps on the average will always have more harmful mutations than those of earlier generations. And remember, just because the polpys don't age doesn't mean they are immortal. They still die, in large numbers, from causes such as being eaten. As the polyps are reproducing and dying, we end up with more polyps from more recent generations and fewer from older generations. The mutational load of the genetic individual increases, and over time this should lead to increased risk of the extinction of the genetic individual. So the genetic individuals, like the cells, senescence, but the two layers of organization in between, the polyps and the clusters, don't.
This is a real problem without a clear solution. Do hydra tell us something important about the evolution of aging, because unlike almost all other animals, they don't age, or are we just looking at the wrong scale?
A more useful way to phrase the question may be to ask why the cell and genetic individual age, but the polp and the cluster don't. The first answer that comes to mind is that both cells and genetic individuals accumulate damage in ways that they can't fully repair, while the polyp and the cluster can easily repair any damage that comes along because any one piece can completely rebuild the whole. In this context, aging occurs when organism are built in a way that doesn't allow for easy repair. At some point this idea will combine with some other idea to form something useful. Or it won't.
I've already talked a little bit about the hyrda, but I want to give you more detail, because they are such an interesting and bizarre case. There are at least four levels at which we could define the individual in hydra. The smallest is the individual cell. Most cells in a hydra are capable of turning into any kind of hydra cell, producing a whole new hydra, and moving on their own. People have turned a whole hydra body inside out, and the cells that were on the outside just become inside digestive cells, and the cells that were on the outside become skin cells, and the community of cells goes on about its business. Second, the polyp, that thing with the tentacles and digestive system we classically think of as the individual animal. It looks like a little animal. It acts like a little animal (in most ways). It hunts, it reproduces itself, it has different cells doing different jobs. Third, there is the physically attached cluster of hydra. Through budding (growing a new hydra-shaped organism off the side of the old one) hydra reproduce asexually, but the buds get to be a fair portion of the size of the parent before separating, and are generally of almost full complexity while still physically and physiologically attached. One or two or occasionally more buds can be growing off the main polyp at the same time, and one could easily see this mass of genetically identical connected cells as one individual, despite the fact that it has multiple sets of tentacles feeding multiple digestive systems. Finally, one could consider that these genetically identical groups of cells remain part of the same individual even after physical separation. The genetic individual could after a short time encompass many thousands of polyps.
At which of these four levels does senescence occur? We know from experimental evidence that the risk of death by individual cells increases with age, so we have senescence in level one. In level two, the polyp, the experimental evidence points to no senescence, and the same goes for level three. At level four we don't have experimental evidence, but Mueller's Ratchet implies that there would be slow senescence of the genetic individual. Without going into details, Mueller's Ratchet is a line of genetic reasoning which makes clear that the number of harmful mutations in an asexually producing population almost always increases with time, where the number could decrease with sexual reproduction. So as the genetic individual of the hydra keeps producing more polyps, the newer polyps on the average will always have more harmful mutations than those of earlier generations. And remember, just because the polpys don't age doesn't mean they are immortal. They still die, in large numbers, from causes such as being eaten. As the polyps are reproducing and dying, we end up with more polyps from more recent generations and fewer from older generations. The mutational load of the genetic individual increases, and over time this should lead to increased risk of the extinction of the genetic individual. So the genetic individuals, like the cells, senescence, but the two layers of organization in between, the polyps and the clusters, don't.
This is a real problem without a clear solution. Do hydra tell us something important about the evolution of aging, because unlike almost all other animals, they don't age, or are we just looking at the wrong scale?
A more useful way to phrase the question may be to ask why the cell and genetic individual age, but the polp and the cluster don't. The first answer that comes to mind is that both cells and genetic individuals accumulate damage in ways that they can't fully repair, while the polyp and the cluster can easily repair any damage that comes along because any one piece can completely rebuild the whole. In this context, aging occurs when organism are built in a way that doesn't allow for easy repair. At some point this idea will combine with some other idea to form something useful. Or it won't.
Sunday, March 01, 2009
Evolutionary challenges to gene engeneering a better human
My friend Terry is a bioengineer, as well as a part time futurist. Much of what people in his field work on (as judged by what Terry talks about when he puts on his futurist hat and has a couple of glasses of wine) is thinking about how to modify the human genome to increase our lifespan and healthspan (I just made up the word healthspan, but I bet someone out there is already using it). Much of my work is to understand how and why we evolved to have the lifespan and healthspan we currently do. My understanding of my work is not promising to my understanding of this part of Terry's colleagues' work. In my view, bioengineering a much longer lived human will be extraordinarily difficult for several reasons.
First, we have a great many systems that seem to fail at about the same age, and there are good evolutionary reasons why this should be. Why bother building a femur that last longer than your heart, or your brain, or your pancreas? So to engineer a much longer-lived human, one has to be prepared to make a large number of changes to see a small effect. Terry counters that there will inevitably be some low-hanging fruit, and I concede this point. Simply by editing out some of the purely harmful mutations in the human gene-pool, we can probably extend average life span by a few months or maybe a couple of years. But because so many things fail at similar ages, no one or two or 100 changes could give us healthy 150 year olds.
Second, many individual genes have an enormous number of different effects in a wide range of systems, tissues and traits. When a gene has more than one effect, this is called pleiotropy, and we are chock full of pleiotropies, most of which we don't yet know about or understand. DNA is not like a blueprint, where you can just erase one wall, re-route a few wires, and draw in a new door. It is more like a vastly sprawling and disorganized system of interacting computer applications, add-ons, duplicates, and operating systems (only without any comprehensible order, annotation or easily understood compartmentalization). Something which functions as part of an unnecessary application may also be used in several disparate parts of the operating system. Modify a line of code and all sorts of unintended things can happen. Evolution has fine-tuned this system of interactions through millions of generations of trial and error, with emphasis on the error. Our best computer simulations are barely able to comprehend the folding of a single amino acid string into a protein, let alone a whole cell or organ or human, and animal models only go so far. So the process to modify evolution's optimization would not be fun, fast or clean. Our various bits are tuned to work together, and most potential single modifications can only move us away from that local optimum.
Terry counters that in many cases what evolution was tuning was utility in the form of health/strength/life vs. cost in the form of calories. A large part of the theory of life-history evolution is based on models where developing organisms have limited nutritional resources to invest in important tasks like growing, healing and reproducing. If one assumes unlimited calories are available, one can theoretically grow, reproduce and heal maximally all at the same time. And in Terry's view (which I can't help but see the wisdom in) anyone who can afford to play with the human genome can also afford plenty of potato chips. For the relevant population, calories are no longer limiting. In fact, we go out of our way to burn extra calories now. Spending calories lavishly to buy a few extra years of life or more garish secondary sexual traits is a win-win. The bioengineers of the future will have the advantage over evolution, because they won't have to worry about one of the main constraints evolution was dealing with, calorie restriction. So we may have to change a few things at once to make it all work well together, but we can do that. We can, in my imagining of Terry's thinking, reengineer the organism to its new environment.
It occurred to me last night that there is third, bigger and more insurmountable barrier to re-tuning. One that is not just a technological limitation: Breeding. Humans have been known to breed with each other, and in doing so they mix their genomes. You have half the genome of your biological father and half the genome of your biological mother. Imagine if your uber-mench father had a carefully altered suite of genes, and your mother was a good old-fashioned non-GMO woman. What do you get? You get half a carefully altered genome mixed with genes they were never designed to interact with. Chances are, you have all sorts of wacky health problems, and greatly reduced longevity. It would be like taking half the code of Mac OS 9 and half the code of OS X and expecting a stable operating system.
This means that every change and group of changes would have to be carefully designed to be back-compatible. The alternatives are gene altering the entire human population (which would never ever ever ever work (and I very rarely use that many "ever"s in a row)) or engineering the longevous new humans to be incapable of interbreeding with the old model. They'd have to start by separating off one population as a seperate species, Homo terrii, and only thereafter get serious about reengineering.
So suppose the engineers decide they want to make everything back compatible?
I'm not convinced this would work either. Most mutations are bad for you not only because they break a piece of the system, but because they make a new piece that doesn't work with what is already there. Requiring back compatibility means we have to have every piece work with not only the old set of genes and the new set of genes, but every possible combination of old and new. Evolution, largely free from constraints of time, funding and ethics, accomplishes this by letting those individuals who have bad combinations die out until there are very few harmful combinations possible. To extend the computer code analogy, this would be like trying to write OS XI in such a way that if one blended the code with OS X, it would still work. It is possible to do, but XI would end up looking an awful lot like X, too similar to be more than a service update.
This leaves only the option of creating a population incapable of breeding with normal humans and altering their genes extensively to try to overcome a large number of age-limiting factors at once. Again my understanding of evolution suggests a major difficulty. To do this successfully, one would need a large population all gene-altered simultaneously, to avoid inbreeding effects. One can't start a new population with just a few individuals and expect that species to have a decent chance of surviving well. Even if the species does make it through, there is likely to be an extended period of decreased lifespan and healthspan while the inbreeding kinks work themselves out and the population increases in size and genetic diversity.
Without doubting that bioengineers will continue to make things that seem impossible become projects of undergraduates, I consider it highly unlikely they will achieve any very significant advances in human longevity in the next few decades.
(NOTE: I sent this to Terry for comment or objection some time ago but he has been busy with 'job' and 'editing the book.' I take his failure to offer a substantive reply as evidence that in some basement deep under campus, his department is already failing to build an immortal human.)
First, we have a great many systems that seem to fail at about the same age, and there are good evolutionary reasons why this should be. Why bother building a femur that last longer than your heart, or your brain, or your pancreas? So to engineer a much longer-lived human, one has to be prepared to make a large number of changes to see a small effect. Terry counters that there will inevitably be some low-hanging fruit, and I concede this point. Simply by editing out some of the purely harmful mutations in the human gene-pool, we can probably extend average life span by a few months or maybe a couple of years. But because so many things fail at similar ages, no one or two or 100 changes could give us healthy 150 year olds.
Second, many individual genes have an enormous number of different effects in a wide range of systems, tissues and traits. When a gene has more than one effect, this is called pleiotropy, and we are chock full of pleiotropies, most of which we don't yet know about or understand. DNA is not like a blueprint, where you can just erase one wall, re-route a few wires, and draw in a new door. It is more like a vastly sprawling and disorganized system of interacting computer applications, add-ons, duplicates, and operating systems (only without any comprehensible order, annotation or easily understood compartmentalization). Something which functions as part of an unnecessary application may also be used in several disparate parts of the operating system. Modify a line of code and all sorts of unintended things can happen. Evolution has fine-tuned this system of interactions through millions of generations of trial and error, with emphasis on the error. Our best computer simulations are barely able to comprehend the folding of a single amino acid string into a protein, let alone a whole cell or organ or human, and animal models only go so far. So the process to modify evolution's optimization would not be fun, fast or clean. Our various bits are tuned to work together, and most potential single modifications can only move us away from that local optimum.
Terry counters that in many cases what evolution was tuning was utility in the form of health/strength/life vs. cost in the form of calories. A large part of the theory of life-history evolution is based on models where developing organisms have limited nutritional resources to invest in important tasks like growing, healing and reproducing. If one assumes unlimited calories are available, one can theoretically grow, reproduce and heal maximally all at the same time. And in Terry's view (which I can't help but see the wisdom in) anyone who can afford to play with the human genome can also afford plenty of potato chips. For the relevant population, calories are no longer limiting. In fact, we go out of our way to burn extra calories now. Spending calories lavishly to buy a few extra years of life or more garish secondary sexual traits is a win-win. The bioengineers of the future will have the advantage over evolution, because they won't have to worry about one of the main constraints evolution was dealing with, calorie restriction. So we may have to change a few things at once to make it all work well together, but we can do that. We can, in my imagining of Terry's thinking, reengineer the organism to its new environment.
It occurred to me last night that there is third, bigger and more insurmountable barrier to re-tuning. One that is not just a technological limitation: Breeding. Humans have been known to breed with each other, and in doing so they mix their genomes. You have half the genome of your biological father and half the genome of your biological mother. Imagine if your uber-mench father had a carefully altered suite of genes, and your mother was a good old-fashioned non-GMO woman. What do you get? You get half a carefully altered genome mixed with genes they were never designed to interact with. Chances are, you have all sorts of wacky health problems, and greatly reduced longevity. It would be like taking half the code of Mac OS 9 and half the code of OS X and expecting a stable operating system.
This means that every change and group of changes would have to be carefully designed to be back-compatible. The alternatives are gene altering the entire human population (which would never ever ever ever work (and I very rarely use that many "ever"s in a row)) or engineering the longevous new humans to be incapable of interbreeding with the old model. They'd have to start by separating off one population as a seperate species, Homo terrii, and only thereafter get serious about reengineering.
So suppose the engineers decide they want to make everything back compatible?
I'm not convinced this would work either. Most mutations are bad for you not only because they break a piece of the system, but because they make a new piece that doesn't work with what is already there. Requiring back compatibility means we have to have every piece work with not only the old set of genes and the new set of genes, but every possible combination of old and new. Evolution, largely free from constraints of time, funding and ethics, accomplishes this by letting those individuals who have bad combinations die out until there are very few harmful combinations possible. To extend the computer code analogy, this would be like trying to write OS XI in such a way that if one blended the code with OS X, it would still work. It is possible to do, but XI would end up looking an awful lot like X, too similar to be more than a service update.
This leaves only the option of creating a population incapable of breeding with normal humans and altering their genes extensively to try to overcome a large number of age-limiting factors at once. Again my understanding of evolution suggests a major difficulty. To do this successfully, one would need a large population all gene-altered simultaneously, to avoid inbreeding effects. One can't start a new population with just a few individuals and expect that species to have a decent chance of surviving well. Even if the species does make it through, there is likely to be an extended period of decreased lifespan and healthspan while the inbreeding kinks work themselves out and the population increases in size and genetic diversity.
Without doubting that bioengineers will continue to make things that seem impossible become projects of undergraduates, I consider it highly unlikely they will achieve any very significant advances in human longevity in the next few decades.
(NOTE: I sent this to Terry for comment or objection some time ago but he has been busy with 'job' and 'editing the book.' I take his failure to offer a substantive reply as evidence that in some basement deep under campus, his department is already failing to build an immortal human.)
Saturday, January 31, 2009
Oldest old
Among my demography colleagues there is considerable academic interest in the 'oldest old,' the people who make 90 year olds seem positively youthful. I once heard a series of talks on "Sardinian Super-Centenarians" (a truly lovely phrase to hear repeated in an Italian accent). So first you're old, then you are really old, then you are a centenarian, then you are a super-centenarian, then, once having turned 100 is ancient history, you get to be oldest old. And once you are oldest old, having outlived many millions of your cohort, lots of people start taking an interest in you. Locals take it as a mark of pride to have someone so incredibly longevous living among them. People wonder what kind of yogurt you eat, and how often. Geneticists want blood samples to find all the things that didn't kill you. Demographers need data on you to know how the rightmost extremes of their graphs of anything over age should look. Is mortality rate higher among 115 year olds than 116 year olds, and what does that tell us about the possibility of increasing human lifespan generally? Is maximum longevity still increasing with improved technology?
It is hard to find very many data points for these questions, and significant resources have been invested in scouring the world for very old people whose ages can be positively verified.
Tuti Yusupova of Uzbekistan is a good example. According to her recently "noticed" birth certificate, she is 128 years old, by far the oldest living person ever recorded. But was the birth certificate really made in 1880, or was it slipped into a folder in 1920 or 2008? Could it be a clerical error? Some priest or bureaucrat may have written the wrong year for some reason. These things are surely being investigated.
And is she the original Tuti? A colleague told me of a case in which a potential oldest woman turned out to have adopted her mother's name, persona and possessions when her mother died. In the process she added 30 years to her age. She was old, but not oldest old. Publicity surrounding her apparent record brought the truth to light. So my colleagues are understandably dubious about the new record holder. If she is that old (which I hope is the case just because a real record is nicer than a fake one) some of my colleagues will have to (slightly) modify their thinking about how long a human being can stay alive.
It is hard to find very many data points for these questions, and significant resources have been invested in scouring the world for very old people whose ages can be positively verified.
Tuti Yusupova of Uzbekistan is a good example. According to her recently "noticed" birth certificate, she is 128 years old, by far the oldest living person ever recorded. But was the birth certificate really made in 1880, or was it slipped into a folder in 1920 or 2008? Could it be a clerical error? Some priest or bureaucrat may have written the wrong year for some reason. These things are surely being investigated.
And is she the original Tuti? A colleague told me of a case in which a potential oldest woman turned out to have adopted her mother's name, persona and possessions when her mother died. In the process she added 30 years to her age. She was old, but not oldest old. Publicity surrounding her apparent record brought the truth to light. So my colleagues are understandably dubious about the new record holder. If she is that old (which I hope is the case just because a real record is nicer than a fake one) some of my colleagues will have to (slightly) modify their thinking about how long a human being can stay alive.
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