30 replies to this topic

[gavrilov]

Greetings,

Recently I came across this new entertaining piece on evolution of aging and longevity:

A Problem for Darwin: Why Do We Age And Die Rather Than Live Forever?
http://blogs.psychol....com/print/3712
and
http://blogs.psychol...er-live-forever

This is a popular review published by Ira Rosofsky, Ph.D. on Psychology Today Blog "Adventures in Old Age," which allows you to post your questions and comments there, if you wish.

See ongoing discussion (2 posts) there:
http://blogs.psychol...orever/comments


Hope it helps,

-- Leonid


----------------------------------------------
-- Leonid Gavrilov, Ph.D.
Center on Aging, NORC/University of Chicago
Website: http://longevity-science.org/
Blog: http://longevity-science.blogspot.com/
My books: http://longevity-sci....org/Books.html

[Prometheus]

Rosofsky is a psychologist.

[brokenportal]

I heard de Grey go over this a few times.

He says that aging was never selected out because we almost always died of something else before aging could get us. If you think about it then, aging may have kind of only been around really, in noticable levels, for the last 100 years or so.

[caston]

Look at what happens sometimes when people get swine or bird flu. Most of the time people don't actually die from the virus they die from the immune response to the virus.
This might not be an accident but an important evolutionary feature.

Perhaps communities survive better in competition with other communties if their members ultruisticly self destruct. Once an animal is dead it no longer serves as a vehicle for infection. These same genes that are responsible for ultruistic self destruction also slowly wind down and destroy the animal in response to increasing levels of pathogens in the animals microbiome.

It is unethical on every level to interfere with this process in any way other than to destroy the pathogens.

[Akagi]

The reason we age is because every time our cells divide, they lose a little bit of their information each time (telomere shortening). Every division shortens the ends by a little bit. To help mitigate this we have some padding in our genes so that gets eaten first, but eventually it starts working on the good stuff and that's where aging kicks in.

Now we have a deactivated gene that allows our cells to produce telomerase and stops this from happening. It's as simple as turning the gene back on, and there are several ways to do this.

However, there is a catch, and it's a big one.

The catch is that if you re-activate these genes, then you've done half the job required for cancer.

The fact that your cells gradually wither away and die is what stops runaway mutation/cell divisions from becoming cancerous all the time. Once you get an uncontrolled growth that keeps acellerating due to a mutation, that cell and all its subsequent cells it produced quickly die off because they experience turbo-aging. It's like a runaway car using up all its gas. Eventually it will burn itself out.

However, if you stopped your cellular aging process, the car would never run out of gas. There would be no limit to the number of times a particular cell could divide. Say you turn on your no-more-aging gene and stop aging. Now say a cell in your body undergoes a mutation that causes it to rapidly divide. Then all that needs to happen is for 1 of the cells that came from that to get another mutation like removing programmed cell death (apoptosis), then 1 cell that came from that cell ignores the limit which stops cells dividing when there are enough in an area (contact inhibition), then further mutations happen on subsequent cells and you have runaway cancer.

For a full rundown, read Telomeres, Telomerase and Cancer

The fact that we have a deactivated gene in our body that enables us not to age indicates that originally we were not supposed to age, but this aspect made it merely a matter of time until we got cancer and died from that, so it had to be deactivated.

[Luna]

The reason we age is because every time our cells divide, they lose a little bit of their information each time (telomere shortening). Every division shortens the ends by a little bit. To help mitigate this we have some padding in our genes so that gets eaten first, but eventually it starts working on the good stuff and that's where aging kicks in.

Now we have a deactivated gene that allows our cells to produce telomerase and stops this from happening. It's as simple as turning the gene back on, and there are several ways to do this.

However, there is a catch, and it's a big one.

The catch is that if you re-activate these genes, then you've done half the job required for cancer.

The fact that your cells gradually wither away and die is what stops runaway mutation/cell divisions from becoming cancerous all the time. Once you get an uncontrolled growth that keeps acellerating due to a mutation, that cell and all its subsequent cells it produced quickly die off because they experience turbo-aging. It's like a runaway car using up all its gas. Eventually it will burn itself out.

However, if you stopped your cellular aging process, the car would never run out of gas. There would be no limit to the number of times a particular cell could divide. Say you turn on your no-more-aging gene and stop aging. Now say a cell in your body undergoes a mutation that causes it to rapidly divide. Then all that needs to happen is for 1 of the cells that came from that to get another mutation like removing programmed cell death (apoptosis), then 1 cell that came from that cell ignores the limit which stops cells dividing when there are enough in an area (contact inhibition), then further mutations happen on subsequent cells and you have runaway cancer.

For a full rundown, read Telomeres, Telomerase and Cancer

The fact that we have a deactivated gene in our body that enables us not to age indicates that originally we were not supposed to age, but this aspect made it merely a matter of time until we got cancer and died from that, so it had to be deactivated.

I don't think it is that simple...
If I remember correctly, usually people who have died haven't spent their telomeres pool yet?

What about other mutations and junk build up in the body, or the body not regenerating part because it's not designed to d so properly or whatever?

[VidX]

I don't think it's that simple either. Basically I'd say it's closely related with replicative senescence, but telomeres are just a fraction of it. My knowledge background is too little to make far fetched claims, but I'm somewhat sure that it's more or less under the supply of stem cells.. I mean - if we replace the damaged pars in the car - we "fix" it and it runs further, but IF the parts we replace are already damaged (reduced stem cell supply, some errors in that shortened supply, etc..) slow decay begins... All the lipofuscins, AGE and other junk.. that's true, but imagine if you turn the clock back to a 18 years old (health) - it suddenly isn't a problem anymore at all, as body repair system is able to remove all the unnecesary junk. So I guess we need to repair the repair systems... to do what hasn't been done over the natural course of evolution.

Edited by VidX, 19 September 2009 - 07:30 PM.

[Aegist]

I have an article on this subject which I wrote a few years ago now, but it seems to be just as relevant now as ever: http://shanegreenup....-do-we-age.html

I strongly recommend reading the paper by Williams GC - 1957. Pleiotropy, Natural Selection, and the Evolution of Senescence. Evolution 11:398-411

I can't find an online version of the full article unfortunately, but I really really enjoy reading it, and strongly recommend it if you can get your hands on it.

Anyway, my favourite basic theory for why organisms have evolved to age is "Antagonistic Pleiotropy", which posits that some genes have positive effects early in life, but unfortunate negative effects later in life. Since survival to reproductive age, and through reproduction are far more heavily weighted in selective stakes, the early benefits are worth more than the 'cost' of the later life negatives. It is possible to have a bunch of offspring before the negative effect kicks in, and thus Evolution would actually select FOR this gene.

Wikipedia has a section on the subject in their article on the evolution of ageing.
http://en.wikipedia....stic_pleiotropy

[Mind]

All the lipofuscins, AGE and other junk.. that's true, but imagine if you turn the clock back to a 18 years old (health) - it suddenly isn't a problem anymore at all, as body repair system is able to remove all the unnecesary junk.

18 year old cells cannot not remove lipofuscin (or other junk) either, they just have a lot less, so it is not a problem.

[DJS]

I suspect that the final verdict will be a combination of theories, but two theories which I view as essential components of a comprehensive theory are antagonistic pleiotropy and maintenance theory.

As I stated previously in another thread, I believe that from an information theoretic perspective (utilizing such concepts as feedback and redundancy), a virtually flawless system is possible. However I do not consider this to be the default state of affairs, or even a likely eventuality in biological evolution.

[Aegist]

I suspect that the final verdict will be a combination of theories, but two theories which I view as essential components of a comprehensive theory are antagonistic pleiotropy and maintenance theory.

Definitely. I am quite convinced that there is no one cause of aging - there is a little truth in all of the theories most likely.

[TheFountain]

I suspect that the final verdict will be a combination of theories, but two theories which I view as essential components of a comprehensive theory are antagonistic pleiotropy and maintenance theory.

Definitely. I am quite convinced that there is no one cause of aging - there is a little truth in all of the theories most likely.

So if you stop hemoglobin glycation, AGEs formation, protein break down and photo-aging you basically end up a 90 year old with the appearance of a 25 year old. Cellular senescence is still occurring but till you control the run away mutations with cell replication you are only controling the appearance of aging? I guess alot of people are going to be asking why that 25 year old walks so funny.

[stevenh]

I would say that aging and death was a species survival characteristic early on in evolution. It would be related to the ecological niche a species competed in. If a species was immortal it would soon exhaust its food supply and die off to a few individuals or none at all. If all species were at once immortal each would compete for a finite food supply and would destroy their own ecological niches. Immortalism was selected out or complexity would have never arisen. But I am coming at this as an "economist" so what do I know? But if one looks at the probabilities, if a species is immortal, over successive generations, of the immortal gene causing a constant rise in a population even if there is a high mortality rate from the stresses of living, one could see that it would not take long for the population of a species to have a very large number of older members. These oldsters would also be favored to pass on their genes. At some point in this steady increase the pressure to evolve might have been removed by sheer success of numbers until the species' ecological niche was degraded and then a sudden die-off without time for natural selection to work its magic.

[DJS]

I would say that aging and death was a species survival characteristic early on in evolution. It would be related to the ecological niche a species competed in. If a species was immortal it would soon exhaust its food supply and die off to a few individuals or none at all. If all species were at once immortal each would compete for a finite food supply and would destroy their own ecological niches. Immortalism was selected out or complexity would have never arisen. But I am coming at this as an "economist" so what do I know? But if one looks at the probabilities, if a species is immortal, over successive generations, of the immortal gene causing a constant rise in a population even if there is a high mortality rate from the stresses of living, one could see that it would not take long for the population of a species to have a very large number of older members. These oldsters would also be favored to pass on their gene At some point in this steady increase the pressure to evolve might have been removed by sheer success of numbers until the species' ecological niche was degraded and then a sudden die-off without time for natural selection to work its magic.

Steven, for the life of me I don't know why so many people share your (with all due respect) entirely incorrect intuitions on aging.

First let me directly address one of the points made in your post. Even without 'immortal organisms', species exhaust their food supplies all the time. This is because of the exponential population growth which is possible via reproduction. The 'predator-prey cycle' and population modulation is something which is well documented and understood in biology. So your entire argument is a no-go.

Also, as I pointed out in another thread (but which bears repeating) in nature organisms very rarely have the privilege of getting old. Usually disease, predation and starvation get them first. Thus, even if one did take group selectionism seriously (which almost no evolutionary biologists do nowadays) there'd be nothing for selection to act on!

However, what I'd really like to challenge is your underlying assumption that immortality or "flawless biological systems" are the default. Let's be clear, this is what you're saying - that it's the normal course of events for biological evolution to produce perfect systems which function without an error rate or any element of internal disorder. This notion is patently false. Here, from a biology textbook I have on my bookcase - - "during the time it takes you to read this sentence, a total of a trillion purine bases will be lost from the DNA of your cells by a spontaneous process called depurination." Obviously, unlike simple mechanistic systems, biological systems possess sophisticated maintenance and repair mechanisms which deal with undesirable 'spontaneous' processes. However this doesn't alter the fact that maintenance and repair mechanisms have evolved to deal with the inherent/preexisting element of disorder which permeates our universe.

Degradation and aging are the default, and something which evolution fights against to varying degrees depending on whether there is strong selection pressure to invest in somatic maintenance. This is supported by the strong correlation between intrinsic and extrinsic mortality. A popular example often given is bats having life spans many times that of most terrestrial rodents which incur a much higher rate of predation. The 'goal' of evolution is to make M&R mechanisms comprehensive enough to keep an organism in relatively pristine condition for as long as it would 'probably' exist with extrinsic mortality factored in (because if the option is available, clearly having the somatic line around to pump out more genetic payload is the superior strategy over costly reproductive cycles with lots of down time, ie, gaps in vertical gene transmission). Any improvements to M&R beyond that are not going to happen because M&R mechanisms are metabolically costly, and evolution is all about being effecient. And finally, there is of course the possibility that the design constraints placed on us by our evolutionary trajectory have created hard limits on the level of life extension that could be produced through evolution by natural selection (versus engineered solutions).

Nothing I have written here is particularly original, I'm only rehashing a lot of the same old arguments... I just wish people would stop with the same busted programmed theory logic. Please people, stop for your own sakes and reevaluate. This one is so obvious to me that I feel a certain amount of embarrassment for people who still don't get it.

[TheFountain]

I would say that aging and death was a species survival characteristic early on in evolution. It would be related to the ecological niche a species competed in. If a species was immortal it would soon exhaust its food supply and die off to a few individuals or none at all. If all species were at once immortal each would compete for a finite food supply and would destroy their own ecological niches. Immortalism was selected out or complexity would have never arisen. But I am coming at this as an "economist" so what do I know? But if one looks at the probabilities, if a species is immortal, over successive generations, of the immortal gene causing a constant rise in a population even if there is a high mortality rate from the stresses of living, one could see that it would not take long for the population of a species to have a very large number of older members. These oldsters would also be favored to pass on their gene At some point in this steady increase the pressure to evolve might have been removed by sheer success of numbers until the species' ecological niche was degraded and then a sudden die-off without time for natural selection to work its magic.

Steven, for the life of me I don't know why so many people share your (with all due respect) entirely incorrect intuitions on aging.

First let me directly address one of the points made in your post. Even without 'immortal organisms', species exhaust their food supplies all the time. This is because of the exponential population growth which is possible via reproduction. The 'predator-prey cycle' and population modulation is something which is well documented and understood in biology. So your entire argument is a no-go.

Also, as I pointed out in another thread (but which bears repeating) in nature organisms very rarely have the privilege of getting old. Usually disease, predation and starvation get them first. Thus, even if one did take group selectionism seriously (which almost no evolutionary biologists do nowadays) there'd be nothing for selection to act on!

However, what I'd really like to challenge is your underlying assumption that immortality or "flawless biological systems" are the default. Let's be clear, this is what you're saying - that it's the normal course of events for biological evolution to produce perfect systems which function without an error rate or any element of internal disorder. This notion is patently false. Here, from a biology textbook I have on my bookcase - - "during the time it takes you to read this sentence, a total of a trillion purine bases will be lost from the DNA of your cells by a spontaneous process called depurination." Obviously, unlike simple mechanistic systems, biological systems possess sophisticated maintenance and repair mechanisms which deal with undesirable 'spontaneous' processes. However this doesn't alter the fact that maintenance and repair mechanisms have evolved to deal with the inherent/preexisting element of disorder which permeates our universe.

Degradation and aging are the default, and something which evolution fights against to varying degrees depending on whether there is strong selection pressure to invest in somatic maintenance. This is supported by the strong correlation between intrinsic and extrinsic mortality. A popular example often given is bats having life spans many times that of most terrestrial rodents which incur a much higher rate of predation. The 'goal' of evolution is to make M&R mechanisms comprehensive enough to keep an organism in relatively pristine condition for as long as it would 'probably' exist with extrinsic mortality factored in (because if the option is available, clearly having the somatic line around to pump out more genetic payload is the superior strategy over costly reproductive cycles with lots of down time, ie, gaps in vertical gene transmission). Any improvements to M&R beyond that are not going to happen because M&R mechanisms are metabolically costly, and evolution is all about being effecient. And finally, there is of course the possibility that the design constraints placed on us by our evolutionary trajectory have created hard limits on the level of life extension that could be produced through evolution by natural selection (versus engineered solutions).

Nothing I have written here is particularly original, I'm only rehashing a lot of the same old arguments... I just wish people would stop with the same busted programmed theory logic. Please people, stop for your own sakes and reevaluate. This one is so obvious to me that I feel a certain amount of embarrassment for people who still don't get it.

Basically all you are saying is 'ya live, ya die'. Which is what other's are arguing against. In fact the purpose of this forum is to argue against and mitigate this seemingly inexorable fact. You said yourself you are stating the obvious. But why? we all know the obvious. Why not argue for reasons against the obvious? Are you turned on by evolutions control over your destiny? But wait, isn't the evolutionary paradigm you are arguing in favor of becomign obsolete? You have to take into account that we are still evolving as a species. That our metabolic signaling pathways are in a state of transition from what they were a hundred thousand years ago. This is because of extreme alterations in life style and brain function. The somatic ecology of our system is now aiming differently than mere efficiency. It is aiming for efficiency and longevity.

We're still in the process of perfecting our choices. Thus the transition continues. Of any rebuttal to this you might have all I can say in advance is why argue in favor or that which discourages people from even trying? I'm sorry but I really don't get your position. You seem very passionate about the fact that there's seemingly nothing we can do to thwart the evolutionary paradigm of aging and decay while other's seem very passionate that we can. But why argue in favor of a hopeless destiny? Why does such a conclusion need to be argued for? If it's inevitable it's inevtiable right? So why waste words on it? *scratches head*

EDIT:
Now with regard to 'The 'predator-prey cycle' we need to distinguish here between species that live intuitively off nature and civilized, domesticated sentient beings. There essentially is no longer a 'predator-prey cycle' in modern civilization. At least one that the majority of us are partaking of regularly. We sit here and talk about it like some national geographic special but really all we are doing is living vicariously through our past. We are over that way of survival, it is a dead paradigm. We are moving on both mentally and genetically. I see no reason for us to act as if we are still foraging through dense jungles in search of our victims. One paradigm removed and another to takes it place. Why can't we talk about what we CAN do instead of what we can't do?

Edited by TheFountain, 25 September 2009 - 04:27 PM.

[DJS]

Basically all you are saying is 'ya live, ya die'. Which is what other's are arguing against. In fact the purpose of this forum is to argue against and mitigate this seemingly inexorable fact. You said yourself you are stating the obvious. But why? we all know the obvious.

Obviously you don't know the obvious because here I am trying to spell it out for you. Let me try to be more clear. (trust me, I'm a nice guy. In real life we'd have this conversation over a beer).

Of any rebuttal to this you might have all I can say in advance is why argue in favor or that which discourages people from even trying? I'm sorry but I really don't get your position. You seem very passionate about the fact that there's seemingly nothing we can do to thwart the evolutionary paradigm of aging and decay while other's seem very passionate that we can. But why argue in favor of a hopeless destiny? Why does such a conclusion need to be argued for? If it's inevitable it's inevtiable right? So why waste words on it? *scratches head*

Hopeless destiny? Hope and belief in the possibility of seeing radical life extension (in my life time) are a driving force for me. As I've said elsewhere, if I didn't think that RLE was possible in my life time, I'd go get a job as an over night security guard and philosophize to the end of my days. Yet here I am busting my ass trying to cram a ton of organic chemistry knowledge into my brain.

The challenge we face is monumental and daunting. The more I learn about biology, the more this fact hits me. What I'd like to caution against is the risk of complacency which I sometimes sense within the transhumanist community. Popping some supplements, eating right, exercising - none of this is going to get the job done. We're all currently scheduled for deletion before 2100. We are fighting for our lives. So yes, live a healthy life style. That's a good thing. But another thing you might consider is becoming a billionaire so you can start pumping millions in R&D for engineered solutions to aging.

Why not argue for reasons against the obvious?

Obvious-not obvious, easy-hard, I couldn't care less. I'm only concerned with the reality of the situation. Misconstruing the problem usually guarantees failure.

Are you turned on by evolutions control over your destiny?

Comments directed towards personal psychology in this manner are a silly waste of time. (and I have no idea where you're coming from with this)

But wait, isn't the evolutionary paradigm you are arguing in favor of becomign obsolete?

Arguing in favor of an evolutionary paradigm? Becoming obsolete? I'm not sure where to begin. There's a level of confusion underlying these comments, but it might be difficult to address them directly. We're discussing aging theory here. To discuss aging theory properly one must have a solid working understanding of evolution. Why? Well, first because aging is an aspect of biology, and evolution by natural selection is seemingly the only way to make any sense of biology. Second, because we are a biological species intimately connected to the rest of the biological world. Remember, Darwin had two ground breaking ideas, evolution by natural selection and common descent. Without this background assumption, homology, model organisms and the success of biomedical research would be nothing less than miraculous.

You have to take into account that we are still evolving as a species.

A debatable and hotly contested point, but again not particularly relevant to the conversation at hand. Whether or not our biology is being 'tweeked' doesn't alter the fact that the tweeking is taking place on a system whose dynamics have evolved over the course of billions of years. There's no way to make heads or tails of the root causes of aging if you're approaching the problem by asking these types of questions.

That our metabolic signaling pathways are in a state of transition from what they were a hundred thousand years ago. This is because of extreme alterations in life style and brain function. The somatic ecology of our system is now aiming differently than mere efficiency. It is aiming for efficiency and longevity.

It seems likely, based on our unusually long lifespans compared to most other mammals, that in our relatively recent evolutionary past (present to 3/4 million years ago) there's been some intense selection pressure for longevity. I've never denied that longevity is an evolvable trait. I just don't see this as a potential solution to our urgent predicament (current expiration date roughly 2060).

[niner]

It seems likely, based on our unusually long lifespans compared to most other mammals, that in our relatively recent evolutionary past (present to 3/4 million years ago) there's been some intense selection pressure for longevity. I've never denied that longevity is an evolvable trait. I just don't see this as a potential solution to our urgent predicament (current expiration date roughly 2060).

DJS, thanks for the excellent posts in this thread. The idea that longevity is evolvable has been considered by others. The argument is that parents will be more successful in passing on their genes if they have the help of some healthy grandparents. Considering the much shorter generational times that were prevalent during most of our evolution, this might even extend to great grandparents, though at some point the added number of mouths to feed might outweigh their usefulness in assuring the passing on of genes. While this may have had some impact in the past, I seriously doubt that it is having any impact at all today. In the modern world, we have largely subverted evolution by ensuring successful procreation by people would previously would not have survived long enough to do so. In effect we are now in a regime of negative evolution as we ensure the survival of the non-fittest.

[DJS]

Hey niner, thanks.

What you've just described is basically how I see things. I'm reminded of the Grandmother hypothesis which I stumbled upon (and found intuitively plausible) when I was pondering the phenomenon of menapause. It should be stressed (and I know you know) that these types of multi-generational evolutionary arguments are based on genic level selection (not group).

Also, in regards to my comment of 'present to 4 mil', I was simply providing a generously inclusive time frame, although generally when I reference our 'ancestrial environment' I have a 100,000+ yrs time frame in mind. I agree that the more we approach the present the more the evolutionary logic begins to blur.

In the modern world, we have largely subverted evolution by ensuring successful procreation by people would previously would not have survived long enough to do so. In effect we are now in a regime of negative evolution as we ensure the survival of the non-fittest.

Yes, minus selection pressure it seems likely that there'd be some negative drift... Also I would mention that, personally, I'm usually cautious in a casual context when broaching this subject as the first thing that comes to most people's mind when discussing fit/unfit in relation to human culture is social darwinism.

[stevenh]

I would say that aging and death was a species survival characteristic early on in evolution. It would be related to the ecological niche a species competed in. If a species was immortal it would soon exhaust its food supply and die off to a few individuals or none at all. If all species were at once immortal each would compete for a finite food supply and would destroy their own ecological niches. Immortalism was selected out or complexity would have never arisen. But I am coming at this as an "economist" so what do I know? But if one looks at the probabilities, if a species is immortal, over successive generations, of the immortal gene causing a constant rise in a population even if there is a high mortality rate from the stresses of living, one could see that it would not take long for the population of a species to have a very large number of older members. These oldsters would also be favored to pass on their gene At some point in this steady increase the pressure to evolve might have been removed by sheer success of numbers until the species' ecological niche was degraded and then a sudden die-off without time for natural selection to work its magic.

Steven, for the life of me I don't know why so many people share your (with all due respect) entirely incorrect intuitions on aging.

First let me directly address one of the points made in your post. Even without 'immortal organisms', species exhaust their food supplies all the time. This is because of the exponential population growth which is possible via reproduction. The 'predator-prey cycle' and population modulation is something which is well documented and understood in biology. So your entire argument is a no-go.

Also, as I pointed out in another thread (but which bears repeating) in nature organisms very rarely have the privilege of getting old. Usually disease, predation and starvation get them first. Thus, even if one did take group selectionism seriously (which almost no evolutionary biologists do nowadays) there'd be nothing for selection to act on!

However, what I'd really like to challenge is your underlying assumption that immortality or "flawless biological systems" are the default. Let's be clear, this is what you're saying - that it's the normal course of events for biological evolution to produce perfect systems which function without an error rate or any element of internal disorder. This notion is patently false. Here, from a biology textbook I have on my bookcase - - "during the time it takes you to read this sentence, a total of a trillion purine bases will be lost from the DNA of your cells by a spontaneous process called depurination." Obviously, unlike simple mechanistic systems, biological systems possess sophisticated maintenance and repair mechanisms which deal with undesirable 'spontaneous' processes. However this doesn't alter the fact that maintenance and repair mechanisms have evolved to deal with the inherent/preexisting element of disorder which permeates our universe.

Degradation and aging are the default, and something which evolution fights against to varying degrees depending on whether there is strong selection pressure to invest in somatic maintenance. This is supported by the strong correlation between intrinsic and extrinsic mortality. A popular example often given is bats having life spans many times that of most terrestrial rodents which incur a much higher rate of predation. The 'goal' of evolution is to make M&R mechanisms comprehensive enough to keep an organism in relatively pristine condition for as long as it would 'probably' exist with extrinsic mortality factored in (because if the option is available, clearly having the somatic line around to pump out more genetic payload is the superior strategy over costly reproductive cycles with lots of down time, ie, gaps in vertical gene transmission). Any improvements to M&R beyond that are not going to happen because M&R mechanisms are metabolically costly, and evolution is all about being effecient. And finally, there is of course the possibility that the design constraints placed on us by our evolutionary trajectory have created hard limits on the level of life extension that could be produced through evolution by natural selection (versus engineered solutions).

Nothing I have written here is particularly original, I'm only rehashing a lot of the same old arguments... I just wish people would stop with the same busted programmed theory logic. Please people, stop for your own sakes and reevaluate. This one is so obvious to me that I feel a certain amount of embarrassment for people who still don't get it.

Hi DJS,

I think it is very difficult to consider this problem because there are no good examples of a complex organism with extreme longevity. When the rabbit was introduced to Australia there was an explosion of the population and then an exhaustion of the food supply and the rabbit population fell all because the rabbit appeared outside of its normal ecological niche. The fact that such examples exist is an argument for an immortal gene never arising because it would make that organism independent of its ecological niche and because of its immortalism it would induce a die-off the species which is of course a contradiction like the paradox of time travel. If the rabbit was immortal it wouldn't have mattered if there were predators or not it would have died out in any ecological niche. There is no advantage to a species in being immortal in fact it could be a detriment to species survival. Of course, humans are different.

[stevenh]

It seems likely, based on our unusually long lifespans compared to most other mammals, that in our relatively recent evolutionary past (present to 3/4 million years ago) there's been some intense selection pressure for longevity. I've never denied that longevity is an evolvable trait. I just don't see this as a potential solution to our urgent predicament (current expiration date roughly 2060).

DJS, thanks for the excellent posts in this thread. The idea that longevity is evolvable has been considered by others. The argument is that parents will be more successful in passing on their genes if they have the help of some healthy grandparents. Considering the much shorter generational times that were prevalent during most of our evolution, this might even extend to great grandparents, though at some point the added number of mouths to feed might outweigh their usefulness in assuring the passing on of genes. While this may have had some impact in the past, I seriously doubt that it is having any impact at all today. In the modern world, we have largely subverted evolution by ensuring successful procreation by people would previously would not have survived long enough to do so. In effect we are now in a regime of negative evolution as we ensure the survival of the non-fittest.

What about Stephen Hawking or FDR surely in a former time they would have been abandoned or would have been marginalized. Simply the fact that we have greater wealth to allocate to the care and survival of these remarkable people is not evidence of negative evolution. But FDR's offspring were not as fortunate as he or as influential. And Hawking's daughter, though smart, does not have her father's brain. Intelligence generally reverts to some mean value in all populations with the occasional outlier, like Hawking. You cannot make judgements apriori where brilliance or worth will arise. It is a mystery.

[niner]

I think it is very difficult to consider this problem because there are no good examples of a complex organism with extreme longevity. When the rabbit was introduced to Australia there was an explosion of the population and then an exhaustion of the food supply and the rabbit population fell all because the rabbit appeared outside of its normal ecological niche. The fact that such examples exist is an argument for an immortal gene never arising because it would make that organism independent of its ecological niche and because of its immortalism it would induce a die-off the species which is of course a contradiction like the paradox of time travel. If the rabbit was immortal it wouldn't have mattered if there were predators or not it would have died out in any ecological niche. There is no advantage to a species in being immortal in fact it could be a detriment to species survival. Of course, humans are different.

There is not an immortality "gene"; it's not a one-gene problem. There are a number of reasons that we age. Aubrey de Grey enumerates seven distinct mechanisms of aging. You can't fix just one; you have to fix them all. To make matters even more difficult, these seven mechanism are not one-gene problems themselves, but multi-gene problems. Thus you can't have a longevity gene arise by a spontaneous random mutation. Any gene that fixes one of the causes of aging is highly likely to have some sort of cost to the organism, such as a more stringent micronutrient requirement or an energetic penalty. If it doesn't have a payoff in terms of survival of progeny, then its costs will cause it to be competed away. "Immortality", which for the sake of this argument I'll define as sufficient longevity to cause resource competition between younger and older members of a group to be a problem, simply isn't going to arise on its own.

[niner]

In the modern world, we have largely subverted evolution by ensuring successful procreation by people would previously would not have survived long enough to do so. In effect we are now in a regime of negative evolution as we ensure the survival of the non-fittest.

What about Stephen Hawking or FDR surely in a former time they would have been abandoned or would have been marginalized. Simply the fact that we have greater wealth to allocate to the care and survival of these remarkable people is not evidence of negative evolution. But FDR's offspring were not as fortunate as he or as influential. And Hawking's daughter, though smart, does not have her father's brain. Intelligence generally reverts to some mean value in all populations with the occasional outlier, like Hawking. You cannot make judgements apriori where brilliance or worth will arise. It is a mystery.

You're missing the point; I'm not saying anything about the worth of those who are kept alive, only that the genetic fitness of the population could be deteriorating instead of improving. If we consider the lack of resistance to a viral pathogen to be a genetic flaw, then FDR's offspring presumably carried his genetic flaw, as do most of us. Europeans who survived the Black Plague were more likely to carry a particular mutation in the CCR5 receptor, and that same mutation is today protective against infection by HIV. Our immune systems were evolved through eons of battle against all manner of pathogens, but that process is being halted by our discovery of antibiotics and antivirals, not to mention sanitation. Every time a person's life is saved by a medical intervention, and they go on to have children, there is a chance they are passing on a maladaptive gene that would otherwise have been culled. This has nothing whatsoever to do with Social Darwinism.

[stevenh]

In the modern world, we have largely subverted evolution by ensuring successful procreation by people would previously would not have survived long enough to do so. In effect we are now in a regime of negative evolution as we ensure the survival of the non-fittest.

What about Stephen Hawking or FDR surely in a former time they would have been abandoned or would have been marginalized. Simply the fact that we have greater wealth to allocate to the care and survival of these remarkable people is not evidence of negative evolution. But FDR's offspring were not as fortunate as he or as influential. And Hawking's daughter, though smart, does not have her father's brain. Intelligence generally reverts to some mean value in all populations with the occasional outlier, like Hawking. You cannot make judgements apriori where brilliance or worth will arise. It is a mystery.

You're missing the point; I'm not saying anything about the worth of those who are kept alive, only that the genetic fitness of the population could be deteriorating instead of improving. If we consider the lack of resistance to a viral pathogen to be a genetic flaw, then FDR's offspring presumably carried his genetic flaw, as do most of us. Europeans who survived the Black Plague were more likely to carry a particular mutation in the CCR5 receptor, and that same mutation is today protective against infection by HIV. Our immune systems were evolved through eons of battle against all manner of pathogens, but that process is being halted by our discovery of antibiotics and antivirals, not to mention sanitation. Every time a person's life is saved by a medical intervention, and they go on to have children, there is a chance they are passing on a maladaptive gene that would otherwise have been culled. This has nothing whatsoever to do with Social Darwinism.

I get your distinction now. But in the human population before civilization these genes existed and were not culled. So, the notion that culling would occur in the absence of modern medical interventions is without support. Doesn't a vaccine produce the same antibodies that the disease itself would produce in the surviving population in the absence of the vaccine? And doesn't this explain why the virus dies out for a time in the human population that has acquired immunity? Evolved immunity would be those mutations that prevent the virus from being successful in a human host. Won't genetic therapies eventually allow the simulation of evolved immunity in humans?

[stevenh]

I think it is very difficult to consider this problem because there are no good examples of a complex organism with extreme longevity. When the rabbit was introduced to Australia there was an explosion of the population and then an exhaustion of the food supply and the rabbit population fell all because the rabbit appeared outside of its normal ecological niche. The fact that such examples exist is an argument for an immortal gene never arising because it would make that organism independent of its ecological niche and because of its immortalism it would induce a die-off the species which is of course a contradiction like the paradox of time travel. If the rabbit was immortal it wouldn't have mattered if there were predators or not it would have died out in any ecological niche. There is no advantage to a species in being immortal in fact it could be a detriment to species survival. Of course, humans are different.

There is not an immortality "gene"; it's not a one-gene problem. There are a number of reasons that we age. Aubrey de Grey enumerates seven distinct mechanisms of aging. You can't fix just one; you have to fix them all. To make matters even more difficult, these seven mechanism are not one-gene problems themselves, but multi-gene problems. Thus you can't have a longevity gene arise by a spontaneous random mutation. Any gene that fixes one of the causes of aging is highly likely to have some sort of cost to the organism, such as a more stringent micronutrient requirement or an energetic penalty. If it doesn't have a payoff in terms of survival of progeny, then its costs will cause it to be competed away. "Immortality", which for the sake of this argument I'll define as sufficient longevity to cause resource competition between younger and older members of a group to be a problem, simply isn't going to arise on its own.

I was using the immortality gene as a catchall for my personal thought experiment on a species whose members were individually immortal or who didn't age i.e., the oldest was as fit as the youngest. I might have erred in thinking that the species would die-off because of a large population putting pressure on a food supply it looks now that the species would achieve a stable population but might not evolve as rapidly because probability would say that the older members would reproduce the most over time though there would be fewer oldsters. DJS talked about evolutionary efficiency and I think of this in terms of, for example, striking a balance between individual risk and the survival of offspring. And in that context the protection of offspring that mammals exhibit comes at a cost to the individual but yet it is an evolved characteristic. But I am still not convinced that aging and death are not species survival characteristics. I am thinking about this. I don't think that it is as settled as others think.

[DJS]

Hey Steven, nice to meet you.

I was using the immortality gene as a catchall for my personal thought experiment on a species whose members were individually immortal or who didn't age i.e., the oldest was as fit as the youngest.

Question. How did the species in your thought experiment become immortal to begin with?

[iconoblast]

I would say that aging and death was a species survival characteristic early on in evolution. It would be related to the ecological niche a species competed in. If a species was immortal it would soon exhaust its food supply and die off to a few individuals or none at all. If all species were at once immortal each would compete for a finite food supply and would destroy their own ecological niches. Immortalism was selected out or complexity would have never arisen. But I am coming at this as an "economist" so what do I know? But if one looks at the probabilities, if a species is immortal, over successive generations, of the immortal gene causing a constant rise in a population even if there is a high mortality rate from the stresses of living, one could see that it would not take long for the population of a species to have a very large number of older members. These oldsters would also be favored to pass on their genes. At some point in this steady increase the pressure to evolve might have been removed by sheer success of numbers until the species' ecological niche was degraded and then a sudden die-off without time for natural selection to work its magic.

Stevenh I think you have the right idea --- if immortality was bad for a population, organisms would evolve a way to self-limit life span to some optimum value that allowed for an ooportunity to reproduce but limited the degree that an individual could dominate the gene pool. You point out one of the many evolutionary disadvantages of immortality: loss of genetic diversity. The people who disagree generally disagree because they think that it is impossible for an organism to evolve a characteristic that is personally (individually) disadvantageous and a self-limited life span is certainly an example.

[iconoblast]

I have an article on this subject which I wrote a few years ago now, but it seems to be just as relevant now as ever: http://shanegreenup....-do-we-age.html

I strongly recommend reading the paper by Williams GC - 1957. Pleiotropy, Natural Selection, and the Evolution of Senescence. Evolution 11:398-411

I can't find an online version of the full article unfortunately, but I really really enjoy reading it, and strongly recommend it if you can get your hands on it.

Anyway, my favourite basic theory for why organisms have evolved to age is "Antagonistic Pleiotropy", which posits that some genes have positive effects early in life, but unfortunate negative effects later in life. Since survival to reproductive age, and through reproduction are far more heavily weighted in selective stakes, the early benefits are worth more than the 'cost' of the later life negatives. It is possible to have a bunch of offspring before the negative effect kicks in, and thus Evolution would actually select FOR this gene.

Wikipedia has a section on the subject in their article on the evolution of ageing.
http://en.wikipedia....stic_pleiotropy

For a discussion of problems with the antagonistic pleiotropy theory see: http://www.programmed-aging.org/theories/antagonistic_pleiotropy.html

[Cameron]

I would say that aging and death was a species survival characteristic early on in evolution. It would be related to the ecological niche a species competed in. If a species was immortal it would soon exhaust its food supply and die off to a few individuals or none at all. If all species were at once immortal each would compete for a finite food supply and would destroy their own ecological niches. Immortalism was selected out or complexity would have never arisen. But I am coming at this as an "economist" so what do I know? But if one looks at the probabilities, if a species is immortal, over successive generations, of the immortal gene causing a constant rise in a population even if there is a high mortality rate from the stresses of living, one could see that it would not take long for the population of a species to have a very large number of older members. These oldsters would also be favored to pass on their genes. At some point in this steady increase the pressure to evolve might have been removed by sheer success of numbers until the species' ecological niche was degraded and then a sudden die-off without time for natural selection to work its magic.

Stevenh I think you have the right idea --- if immortality was bad for a population, organisms would evolve a way to self-limit life span to some optimum value that allowed for an ooportunity to reproduce but limited the degree that an individual could dominate the gene pool. You point out one of the many evolutionary disadvantages of immortality: loss of genetic diversity. The people who disagree generally disagree because they think that it is impossible for an organism to evolve a characteristic that is personally (individually) disadvantageous and a self-limited life span is certainly an example.

I too agree that there are likely evolutionary forces keeping immortality at bay. We have to take into account that it has already been seen that individuals can be screwed to varying degrees for the benefit of the group(e.g. some salmon and their death mechanics, some insects and the loss of reproductive ability for the benefit of a few that can reproduce, in a more general way the soma and the germline if you assume individual cells can be considered 'individuals'. There's also the incest avoidance mechanism, which while fine to stop inbreeding, also creates disgust towards sex with individuals who one grew up closely with, which may have no genetic relationship... while at the same time providing an easier to acquire mate. That is the individual loses the ability to acquire an easier genetically unrelated mate, local and well-known, something that benefits him immediately[can reproduce more easily] in exchange for inbreeding avoidance, something that takes several generations to have significant impact on the group not the individual.). I've also heard that some aging of the cardiovascular system is already evident during early adolescence, which should definitely cause a slight performance decline during a period of strong natural selection force.

There's also the observed fact that within closely related species there can be exponential differences in lifespan, even within some species different members may show exponentially different lifespan, despite sharing the same genome. You also have to take into account that individuals often take measures to help genetically related individuals, even sperm is said to aid sperm of genetically related males and hinder unrelated males in the fertilization of females, there are grandfathers|mothers fathers|mothers and brothers|sisters. Immortality or agelessness would not only allow such individuals to remain reproductive, but even if they did not reproduce a Young-Arnold-Swarchenegger highly experienced hunter grandpa|Uncle could help his grandson|nephew out-compete unrelated kids|adolescents|adults in hunt|reproduction|survival, far better than a decrepit|weak old grandpa|uncle(Such help would confer a substantial advantage on said grandkids that carry genes that allow for charitable ageless granpas|uncles.).

Edited by Cameron, 31 January 2010 - 05:15 PM.

[boyko]

Greetings Leonid and Natasha!

I have taken part in discussion of this article on http://www.psycholog...orever/comments

My answer:


«Programmed aging» once more «Programmed aging»  -- An answer to why we age





Friedrich Leopold August Weismann was in the right about that ageing and death, is «something secondary arisen during adaptation».

 

Ageing evolution has begun with immortal species. Why has won ageing? Ageing accelerates speed of speciation

I know opinion of spouse L.А. and N.S. Gavrilov (Gavrilov, Gavrilova, 2002), Weismann’s ideas (Weismann, 1889) that ageing and death, is «something secondary arisen during adaptation» (the theory of programmed death), call precisely "deceased".  

Our answer:

 

Adv. gerontol. 2009. Vol. 22, № 4. P. 588–595

O. G. Boyko, Yu. A. Labas , A. V. Gordeeva

AN OUTLINE ON THE PHYLOGENETIC HISTORY OF METAZOA AGING PHENOMENON (TO THE STUDY OF A NUMBEROF DOMINEERING PSEUDO SCIENTIFIC CONCEPTS IN AGING BIOLOGY)

I. I. Mechnikov Odessa National University, 2 Dvoryanskaya ul., Odesa65026, Ukraine;

e-mail: boyko-l@rambler.ru

 

Natural selection is just one of the factors determining genome evolution of Metazoa. But it’s not a domineering one along with non-adaptive processes: horizontal gene transfer and input of egoistic genetic elements. That’s why in phylogenesis 1) there are more genes of first Metazoa lost than new ones acquired; 2) the appearance of new genes among Metazoa branches is a very rare occasion; 3) genetically Metazoa is a homogeneous group of species with similar set of cellular mechanisms which was established in the course of evolution. The genome of first Metazoa turned to be so successful that evolution connected with organism amplification didn’t demand radical changes in the genetic repertoire but it demanded changes in DNA sites regulating genes work. These facts along with the fact of existence of species of Metazoa with negligible aging overturn the core theories of aging biology which consider this or that cellular mechanism to be the initiating factor of organism’s aging as sets of cellular mechanisms in aging and non-aging Metazoa forms are practically identical. That’s why the basis of aging biology is in essence a collection of theories and dogmas that have never been proved but which are still in use and which have since long ago turned into a dangerous myth standing in the way of progress. If we are interested in progress of biogerontology a number of domineering pseudo scientific dogmas must be revisited. The matter of conservatism in this issue is inappropriate.

 

http://www.gerontology.ru/PDF_YG/AG_2009-22-04.pdf

 

2. Gerontology in marasmus. A live illustration to New Testament:- « For the time will come when they will not endure sound doctrine;  but wanting to have their ears tickled , they will accumulate for themselves  teachers in accordance to their own desires;and will turn away their ears from the truth, and will turn aside to myths. (2 Timothy 4:3;4)»

Ageing programs are known for a long time. They are fundamental facts. Gerontologists do not wish them to notice, and to discuss myths. For example, here one of such programs of ageing.

http://elementy.ru/g...tracts?artid=79

 

 

Aging it's as easy as pie, than AK-47 Kalashnikov's assault rifle. A tortious act of stochastic processes (free radical reactions and so on)  is programmed  i.e. possibility to grow old.

 

Edited by boyko, 16 March 2010 - 12:41 PM.

[Lassus]

Im going to post this here, since it seems im unable to start new topics.
Is there some post count threshold i have to reach before being able to start new topics? Or perhaps i have to be a paying member or something along those lines.

Anyway, heres an interesting article. I hope it hasnt been posted before.


The author makes a case for programmed ageing, and telomeres playing an important regulatory role. She basically suggests senescence is an evolutionarily developed trait that favours group level selection, instead of the generally accepted view of it being an epiphenomenon that just hasnt been selected against on a per individual basis.

"
The evolution of ageing

Abstract

Ageing is one of biology's longstanding enigmas—a problem that has perplexed both medical gerontologists and evolutionary biologists alike. One of the most prominent theories on the biochemical causes of ageing is the telomere-cell senescence theory. This theory proposes that ageing is due to the build up of telomere-induced senescent cells within the body. From an evolutionary standpoint, this system is thought to have evolved via antagonistic pleiotropy. Under this view, ageing is seen as a side effect of the telomere-cell senescence system, with the primary function of it being to defend against cancer. However, there are a number of problems with interpreting the system in this way, and several lines of evidence suggest that it was selected first and foremost to cause ageing. This logically entails the view that ageing is adaptive—an idea that is currently controversial."

http://biohorizons.o...ent/3/1/77.full


I really hope she is right and ageing is an adaptive thing instead of something nature just didnt consider worth fixing from a species fitness perspective. It would make finding solutions so much easier ill wager.