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I actually thought this article did a pretty good job explaining why we age. As pointed out, our bodies fall apart because they are the product of an evolutiona

by jostmey 12y ago

I actually thought this article did a pretty good job explaining why we age. As pointed out, our bodies fall apart because they are the product of an evolutionary process. Our genetic code is like a computer program that runs into a bunch of fatal errors after it has been left running for too long. These fatal errors do not matter to our genes provided enough time has elapsed since our birth for our DNA to pass on several copies of itself. There is simply an absence of selective pressure for us to live past a certain reproductive age. (If I wrote in laymen's terms it is because I am a laymen on the issue, but a well informed one at that.)

ars 12y ago
Yes, that is one explanation, but it's refuted by other evidence. (And the article covers this.) The main problem with the argument is that our body does a great job of fixing errors - so why does that process suddenly seem to stop? Why not just keep on fixing errors. If you can fix errors for 40 years why stop there? Why does the process suddenly stop at that age? It's not like there is a gradual accumulation of errors - it's no errors for 40 years, then suddenly error correction mode is switched off. Why? It also just raises the question of why there is a reproductive age in the first place? Why does that stop? (For women anyway - it doesn't seem to stop for men, so the evolutionary argument fails there too.) But the biggest argument against that theory is other animals. Why do they have different lifespans? The genetic machinery for all mammals is more or less the same.
- jostmey 12y ago
  First of all, there are a number of things that go wrong in our bodies as we age. Certainly genetic errors build up over time and are left uncorrected. But this is just one of many things that go wrong. The reason our bodies are allowed to degrade in the first place is because we have usually already survived well into our reproductive age. The evolutionary theories of aging actually provide a pretty solid explanation as to why separate species have different lifespans. Some species take longer to reach reproductive maturity than others. Some species reproduce more slowly than others, which in turn effects how quickly the animal may age. Individuals in some species don't survive very long due to external pressures such as starvation and predation, which also shapes lifespan. The best introduction into the evolutionary theories of aging I have found is: http://www.genetics.org/content/156/3/927.full.pdf http://www.genetics.org/content/156/3/927.full.pdf . It is worth noting this theory explains human mortality curves once external causes of death have been removed.
  - crystaln 12y ago
    Would it not make more evolutionary sense to remain reproductively capable for hundreds or thousands of years? The motive for genes to reproduce does not end after a single set of offspring. In fact, I don't think the motivation is even reduced.
    - hrjet 12y ago
      A large life-span would starve the younger generations of resources. And the younger generations are probably more crucial to the survival of the gene pool, than the older generations for various reasons. One reason is that younger generations might be better adapted to the environment because of mutations. Another reason could be that the brains and bodies of older generations will eventually get saturated / tired. Keeping them alive is inefficient for the species.
      - VLM 12y ago
        "Keeping them alive is inefficient for the species." A lot of that is based on the idea of a nuclear American 1950s family, mom dad and 2.5 kids in a house and grannie lives in Florida 1000 miles away. More likely, if I lived for 1000 years I'd spend a lot of time ensuring the economic success of my descendants by teaching programming, electronics, maybe math unless a better mathematician comes along. If this situation existed in the past, I have a GGGGG-uncle (cousin?) who was a Harvard literature prof in the early 1800s and I'm sure he would have taken a decade out of his semi-eternal life to educate me on English lit and related topics. I have some GGGG-Uncles who were in the civil war and fought in Tennessee, surely their personal experiences would have more impact than merely reading a book. This has certain economic and evolutionary effects, such that a "migrant farm harvesting laborer" not allowed to ever benefit from his own labor, would not be able to help his GGGG-grandkids in any obvious way. So some kids are going to grow up with 16 hours a day of continuous one on one academic tutoring from a team of perhaps a dozen PHD ancestors, while other kids are going to grow up basically playing video games, or at best, watching youtube videos. Its an obvious sci-fi topic to explore the nature vs nurture question. A permanent overclass would likely develop based solely on ancestry (indirectly "nature" although in practice "nurture") This is aside from obvious social interaction. Locally I know a lot of the people in my field, and a descendent going into my line of work could be financially (aka reproductively) rewarded by hanging out with me and meeting people. If I do nothing for a descendent other than socially introduce them to local hiring managers, that's still genetically a net win. Everyone else will be doing the same thing so I will have to keep up.
- chrisdone 12y ago
  I like how all the replies to your post are appealing to tradition. “If you lived forever you'd starve people of resources and never evolve, that'd be bad!” If you lived forever, you wouldn't need to evolve, because you wouldn't be dying due to the environment. If you are still alive: you are well suited to be. Reproduction is just a form of genetic immortality if not individual immortality. All of this presupposes that some immortal people were born and just died out because being immortal wouldn't be rewarded by reproducing. And ignores the fact that animals that live for a very long time reproduce slower than animals that live for a short time.
- bjeanes 12y ago
  > The main problem with the argument is that our body does a great job of fixing errors - so why does that process suddenly seem to stop? Why not just keep on fixing errors. If you can fix errors for 40 years why stop there? Why does the process suddenly stop at that age? Because then you compete for resources with your offspring and limit the chances of passing on your genetic code.

by jostmey 12y ago

ars 12y ago

Yes, that is one explanation, but it's refuted by other evidence. (And the article covers this.) The main problem with the argument is that our body does a great job of fixing errors - so why does that process suddenly seem to stop? Why not just keep on fixing errors. If you can fix errors for 40 years why stop there? Why does the process suddenly stop at that age? It's not like there is a gradual accumulation of errors - it's no errors for 40 years, then suddenly error correction mode is switched off. Why? It also just raises the question of why there is a reproductive age in the first place? Why does that stop? (For women anyway - it doesn't seem to stop for men, so the evolutionary argument fails there too.) But the biggest argument against that theory is other animals. Why do they have different lifespans? The genetic machinery for all mammals is more or less the same.

jostmey 12y ago
First of all, there are a number of things that go wrong in our bodies as we age. Certainly genetic errors build up over time and are left uncorrected. But this is just one of many things that go wrong. The reason our bodies are allowed to degrade in the first place is because we have usually already survived well into our reproductive age. The evolutionary theories of aging actually provide a pretty solid explanation as to why separate species have different lifespans. Some species take longer to reach reproductive maturity than others. Some species reproduce more slowly than others, which in turn effects how quickly the animal may age. Individuals in some species don't survive very long due to external pressures such as starvation and predation, which also shapes lifespan. The best introduction into the evolutionary theories of aging I have found is: http://www.genetics.org/content/156/3/927.full.pdf http://www.genetics.org/content/156/3/927.full.pdf . It is worth noting this theory explains human mortality curves once external causes of death have been removed.
- crystaln 12y ago
  Would it not make more evolutionary sense to remain reproductively capable for hundreds or thousands of years? The motive for genes to reproduce does not end after a single set of offspring. In fact, I don't think the motivation is even reduced.
  - hrjet 12y ago
    A large life-span would starve the younger generations of resources. And the younger generations are probably more crucial to the survival of the gene pool, than the older generations for various reasons. One reason is that younger generations might be better adapted to the environment because of mutations. Another reason could be that the brains and bodies of older generations will eventually get saturated / tired. Keeping them alive is inefficient for the species.
    - VLM 12y ago
      "Keeping them alive is inefficient for the species." A lot of that is based on the idea of a nuclear American 1950s family, mom dad and 2.5 kids in a house and grannie lives in Florida 1000 miles away. More likely, if I lived for 1000 years I'd spend a lot of time ensuring the economic success of my descendants by teaching programming, electronics, maybe math unless a better mathematician comes along. If this situation existed in the past, I have a GGGGG-uncle (cousin?) who was a Harvard literature prof in the early 1800s and I'm sure he would have taken a decade out of his semi-eternal life to educate me on English lit and related topics. I have some GGGG-Uncles who were in the civil war and fought in Tennessee, surely their personal experiences would have more impact than merely reading a book. This has certain economic and evolutionary effects, such that a "migrant farm harvesting laborer" not allowed to ever benefit from his own labor, would not be able to help his GGGG-grandkids in any obvious way. So some kids are going to grow up with 16 hours a day of continuous one on one academic tutoring from a team of perhaps a dozen PHD ancestors, while other kids are going to grow up basically playing video games, or at best, watching youtube videos. Its an obvious sci-fi topic to explore the nature vs nurture question. A permanent overclass would likely develop based solely on ancestry (indirectly "nature" although in practice "nurture") This is aside from obvious social interaction. Locally I know a lot of the people in my field, and a descendent going into my line of work could be financially (aka reproductively) rewarded by hanging out with me and meeting people. If I do nothing for a descendent other than socially introduce them to local hiring managers, that's still genetically a net win. Everyone else will be doing the same thing so I will have to keep up.
chrisdone 12y ago
I like how all the replies to your post are appealing to tradition. “If you lived forever you'd starve people of resources and never evolve, that'd be bad!” If you lived forever, you wouldn't need to evolve, because you wouldn't be dying due to the environment. If you are still alive: you are well suited to be. Reproduction is just a form of genetic immortality if not individual immortality. All of this presupposes that some immortal people were born and just died out because being immortal wouldn't be rewarded by reproducing. And ignores the fact that animals that live for a very long time reproduce slower than animals that live for a short time.
bjeanes 12y ago
> The main problem with the argument is that our body does a great job of fixing errors - so why does that process suddenly seem to stop? Why not just keep on fixing errors. If you can fix errors for 40 years why stop there? Why does the process suddenly stop at that age? Because then you compete for resources with your offspring and limit the chances of passing on your genetic code.