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Author Topic:   Is death a product of evolution
2ice_baked_taters
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Message 1 of 46 (361016)
11-03-2006 12:08 AM


Much focus in evolution concerns the genesis of life. The evolution or branching of one specie into another or many others. I have begun to wonder how it is that death might be explained by evolution.

The chemical reactions that compose what we call biology....They are all relatively short lived. There are some notable exceptions in the plant world but this chemical process has built in limits for every species. How might death be explained by evolution? Is death an integral part of evolution {in other words, evolution not being possible without death} or, is it an adaptation of biological things?

I am of course referring to a natural death where the body simply breaks down or wears out. How does evolution account for the winding down of the process after the big wind up? I have searched the net several times and have not come up with anything notable.

Edited by AdminPhat, : spellcheck


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Message 2 of 46 (362597)
11-08-2006 8:21 AM


Thread moved here from the Proposed New Topics forum.
    
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Message 3 of 46 (363172)
11-11-2006 3:49 AM


I think death is a vital part of the process of evolution. Mutations could not be distinguished as helpful, harmless, and harmful without it - except for those which affect reproduction directly, which could not by themselves have produced all the variety of life. Also you'd need an endless external supply of food and unlimited space.
  
Dr Jack
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Message 4 of 46 (363181)
11-11-2006 7:13 AM
Reply to: Message 1 by 2ice_baked_taters
11-03-2006 12:08 AM


I think the most convincing answer I've seen is simply this:

From an evolutionary point of view a mutation that gives an advantage early in life at the cost of a disadvantage later on (or an earlier death) will be selected for, because the possessor will outcompete others other the birth->reproduction cycle.


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Hyroglyphx
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Posts: 5622
From: Austin, TX
Joined: 05-03-2006


Message 5 of 46 (363305)
11-11-2006 10:19 PM
Reply to: Message 1 by 2ice_baked_taters
11-03-2006 12:08 AM


The Law of death
How might death be explained by evolution? Is death an integral part of evolution {in other words, evolution not being possible without death} or, is it an adaptation of biological things?

Death would certainly be an integral part of evolution simply by the virtue that death is an important part of life. If nothing ever died but reproduction rates remained, there would be an overabundance of organisms. Is it critical in the aspect of whether or not evolution would be possible, not really. The only aspect is competition. But if something cannot die then competition for food is pointless. Food would be pointless for the immortal.

But I have often wondered why no one in the scientific field has not classified death as a physical law. Everything dies. This fact alone makes it reasonable to refer to it as a natural law. Why has this phenomenon not been named in terms of being a law? Would that incorporate the 2nd Law of Thermodynamics? All things wind down, which is essentially the greatest portion of the law.

What then is the Law of death called?


"The weapons of our warfare are not carnal but mighty in God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God." -2nd Corinthians 10:4-5
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Modulous
Member (Idle past 178 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 6 of 46 (363307)
11-11-2006 10:42 PM
Reply to: Message 4 by Dr Jack
11-11-2006 7:13 AM


Pleiotropy, Natural Selection, and the Evolution of Senescence
Williams (1957)

quote:
The selective value of a gene depends on
how it affects the total reproductive
probability. Selection of a gene that confers
an advantage at one age and a disadvantage at
another will depend not only on the
magnitudes of the effects themselves, but also
on the times of the effects. An advantage
during the period of maximum reproductive
probability would increase the total
reproductive probability more than a
proportionately similar disadvantage later on
would decrease it. So natural selection will
frequently maximize vigor in youth at the
expense of vigor later on and thereby produce
a declining vigor (senescence) during adult
life. Selection, of course, will act to minimize
the rate of this decline whenever possible.
The rate of senescence shown by any species
will reflect the balance between this direct,
adverse selection of senescence as an
unfavorable character, and the indirect,
favorable selection through the age-related
bias in the selection of pleiotropic genes.

Nothing much to add to that - but it makes for an interesting read. I'm fairly sure the science has moved forwards a lot from there, but Williams is such an accessible science writer, I thought I'd include his paper in this thread for those interested in it.


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Modulous
Member (Idle past 178 days)
Posts: 7789
From: Manchester, UK
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Message 7 of 46 (363310)
11-11-2006 10:59 PM
Reply to: Message 5 by Hyroglyphx
11-11-2006 10:19 PM


Re: The Law of death
. But if something cannot die then competition for food is pointless. Food would be pointless for the immortal.

The critical part of the OP is that it is talking about dying of 'natural causes' that is to say: of old age. Why do bodies grow old and die? Would it not be evolutionarily 'stable' to live longer and have more children and look after them and have more children and so on and so on?

Genes replicate therefore they are - a set of genes that managed to create a machine capable of replicating its genes until it was killed by an enemy/predator/accident etc would have a huge selective advantage over other gene machines that slowly grew old, stopped spreading genes and died.

Its a great and valid question to ask of evolution, since a simple look at evolution would have us believe that animals should be living longer and longer - yet we don't!


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Hyroglyphx
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Posts: 5622
From: Austin, TX
Joined: 05-03-2006


Message 8 of 46 (363312)
11-11-2006 11:17 PM
Reply to: Message 7 by Modulous
11-11-2006 10:59 PM


Re: The Law of death
The critical part of the OP is that it is talking about dying of 'natural causes' that is to say: of old age. Why do bodies grow old and die?

Well, this is why I wanted to know why no one has named a law of death into the annals of physical law. Why do our bodies grow old and die? Is apart of the 2LoT? What kinds of evolutionary effects would it have if organisms would live longer? Would that effect the rate of reproduction?

Its a great and valid question to ask of evolution, since a simple look at evolution would have us believe that animals should be living longer and longer - yet we don't!

Yeah, I mean we'd have to consider the advantage of natural selection choosing the healthier gene pool. Why hasn't it effected the mortality rate overall? At the same time, what disadvantages would they pose to any given organism? If they lived longer, there would be more competition because all organisms would presumably reproduce longer. The exponential population growth would be astronomical. It sounds very give or take. It sounds that nature/God knows what it/He is doing.


"The weapons of our warfare are not carnal but mighty in God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God." -2nd Corinthians 10:4-5
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Modulous
Member (Idle past 178 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 9 of 46 (363313)
11-11-2006 11:32 PM
Reply to: Message 8 by Hyroglyphx
11-11-2006 11:17 PM


Re: The Law of death
Why do our bodies grow old and die? Is apart of the 2LoT?

No - our cells replace themselves so the cells you have at 50 are different than the cells when you are 10. If you kept the same cells all your life you would eventually 'wear down', but that isn't what is going on in biology.

Well, this is why I wanted to know why no one has named a law of death into the annals of physical law.

Scientific laws are usually formal statements rather than 'things die'. I suppose one could say that there is an empirical law of death. I think it is simpler to refer to fact of death than require some kind of law (because theoretically a life could exist that would never die of old age).

Why hasn't it effected the mortality rate overall?

One proposed theory discusses it in terms of pleitropy. I referenced the paper in a post just above this one.

The exponential population growth would be astronomical.

Actually - no. The population would still have a peak value at which level enough members do not survive long enough to reproduce. This would have the effect of balancing the population size out (we see it today anyway - most organisms do not live long enough to die of old age).

Any race of beings that didn't die of old age would either have to exponentially increase its resources to account for the population growth, or it would find its growth cut short. At that point, any genes that provided for a long life would not be selected for (or might even be selected against), and so they would probably lose it.

And so - a population would never be in a stable state with no aging process.


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Taz
Member (Idle past 1365 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006


Message 10 of 46 (363325)
11-12-2006 12:20 AM
Reply to: Message 8 by Hyroglyphx
11-11-2006 11:17 PM


Re: The Law of death
nj writes:

Why do our bodies grow old and die?


Simply put, aging is a disease that has plagued this world since the beginning of life. Think of it more in terms of cancer and other noncommunicable diseases.

This disease is due to imperfections in mitosis that results in minute DNA damage each time that accumulates over long periods of time.

What kinds of evolutionary effects would it have if organisms would live longer?

The question should be why hasn't evolution weeded out this disease long ago? The answer, I think, is simpler than what most people make it out to be. It is simply that organisms don't need to live forever for the species to survive. In fact, an organism that lives longer can sometimes have a negative impact on the population. For one thing, if mommy and daddy don't die for 3 centuries, there would be more old people around consuming resources and putting great stress on the natural resources.

But hypothetically let us say that a non-aging species exists. The chances for this species to go extinct is much higher than other species simply because it is unable to adapt to changes in the surrounding environment.

Yeah, I mean we'd have to consider the advantage of natural selection choosing the healthier gene pool.

How so? Natural selection is not some kind of conscious being that favors good health over poor health, whatever that means.

As long as the individuals are able to live just long enough to pass on their genes by reproduction, there is no reason why a group of individuals that immediately dies from poor health after they make babies are weeded out be natural selection.

It sounds that nature/God knows what it/He is doing.

Actually, it sounds more like any species in the past that was able to achieve such long life eventually died out due to limited resources.

You really need to understand that the kind of ecosystems you see today aren't the firsts and they aren't the lasts either. Our climate changes over time. Allele frequencies change over time. Heck, even the directions of the wind change over time. All of it means that the ecosystems have to change with the surrounding environments. If any species somehow manages to survive long enough to exert too great a pressure on the resources, it would (1) slow starve until some kind of equilibrium is reached, (2) it would migrate to other areas, or (3) find alternative ways to replenish its resources. Sounds familiar?


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Hyroglyphx
Member
Posts: 5622
From: Austin, TX
Joined: 05-03-2006


Message 11 of 46 (363430)
11-12-2006 4:19 PM
Reply to: Message 9 by Modulous
11-11-2006 11:32 PM


Re: The Law of death
our cells replace themselves so the cells you have at 50 are different than the cells when you are 10. If you kept the same cells all your life you would eventually 'wear down', but that isn't what is going on in biology.

Certinaly our cells replicate. And you'd probably be right that if they didn't we'd wear out a whole lot faster than we do through a natural death. Lets extend my meaning a bit further then. Why, if our cells replicate, is this not an ongoing process within our bodies when life (biology) is continually going? I know that telomeres play a large role in cell aging/death. What should happen if we could reverse any of these processes? Why do we die Modulous? I guess that's the simplest way to word the question.

Scientific laws are usually formal statements rather than 'things die'.

That's exactly my point. Why haven't any formal statements concerning death have been annotated somewhere in the annals of physical law? Its seems like such a profound law that the phenomena should be rightly named. I guess I'm just looking for something more cerebral than just saying 'everything that lives will eventually die.'

I suppose one could say that there is an empirical law of death. I think it is simpler to refer to fact of death than require some kind of law (because theoretically a life could exist that would never die of old age).

Theoretically life could exist apart from death. But nothing has managed to stave off death indefinitely. If it is factually accurate to say that everything that lives will eventually die, why not refer to that as a formal law, such as Newtons laws of motion? Its so profound and nothing has been able to circumvent the authority of death that I scarcely see why we shouldn't assign it a formal name.

The population would still have a peak value at which level enough members do not survive long enough to reproduce. This would have the effect of balancing the population size out (we see it today anyway - most organisms do not live long enough to die of old age).

My scenario was assuming that all organisms died of old age rather than from accidental death or succumbing to predation. What affects would that have on all populations? As a result, almost all organisms might invariably die at younger ages than their progenitors.

Edited by nemesis_juggernaut, : edit to add


"The weapons of our warfare are not carnal but mighty in God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God." -2nd Corinthians 10:4-5
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Modulous
Member (Idle past 178 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 12 of 46 (363435)
11-12-2006 4:32 PM
Reply to: Message 11 by Hyroglyphx
11-12-2006 4:19 PM


Re: The Law of death
Why do we die Modulous?

I've summarized one particular theory that deals with growing old and dying. If you didn't catch my post, or the post were I referred you to the post, you can read a scientific paper on this very subject. It also discusses some previous hypotheses that were falsified.

Why haven't any formal statements concerning death have been annotated somewhere in the annals of physical law?

Because when I say formal, I mean mathematically based. Life and Death aren't mathematically describable entities.

But nothing has managed to stave off death indefinitely. If it is factually accurate to say that everything that lives will eventually die, why not refer to that as a formal law, such as Newtons laws of motion?

It is a fact not a law because you can't state it using formal language (ie maths)

Actually, one could state it formally, but it would provide absolutely no utility. One couldn't use the equation (which would be the mathematical equivalent of the fact) to divine any information. It would be pointless, basically. There is no need for such a law. I know some laws (like the 0th law of thermodynamics) seem bloody obvious, but it is also required to correctly proceed with thermodynamics. The Law of Death would not be needed for anything. We can just refer to it as the fact of death.

My scenario was assuming that all organisms died of old age rather than from accidental death or succumbing to predation. What affects would that have on all populations? As a result, almost all organisms might invariably die at younger ages than their progenitors.

Your scenario was discussing organisms that lived longer and so their population sizes grow in response. I said that the population size might grow, but it would be limited to the resources available to the population. As such, life expectancy will likely deteriorate and genes which allow for longer life will cease to be positively selected for and would eventually cease their function and the population's maximum life span will be reduced.

The effect? It would mean the population size will vary between being overpopulated to being underpopulated around an equilibrium point. Something we see to this day.

Edited by Modulous, : No reason given.


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Modulous
Member (Idle past 178 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 13 of 46 (363436)
11-12-2006 4:51 PM
Reply to: Message 10 by Taz
11-12-2006 12:20 AM


immortality = more young not more old!
For one thing, if mommy and daddy don't die for 3 centuries, there would be more old people around consuming resources and putting great stress on the natural resources.

Careful. If we don't get older until older - there wouldn't be more old people around. They were be more youthful people around. There'd be less old people around because more youthful people would die through predation/accident/murder/suicide etc.

And of course, if you want to think of the scenario where senescence sets in at the same time, but takes longer to complete its course, we would have more old people around, but they would be more susceptible to predation/accident etc so they would still die.

It is tempting to think of things from a human perspective, but we are a rare exception as far as animals dying of old age goes - I think it is only some of the larger/smarter organisms that get this accolade (turtles/elephants/primates). Mostly everyone else gets selected out of the gene pool much earlier :)

It is simply that organisms don't need to live forever for the species to survive.

But an organism doesn't care about its species. As long as it doesn't adopt a strategy that is directly harmful to its environment (such as killing off all mates), an organism that has a long life gene will live longer and will produce more children which can also live longer (even if - in the long term - that would be harmful to the species).
It would be advantageous for genes to create beings that lasted as long as is physically possible to spread as many copies of themselves as possible. Living longer means your alleles increase in frequency and as such it should be something that gets positively selected for.

The puzzle then, is why don't we see such creatures?

Edited by Modulous, : No reason given.


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RAZD
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Message 14 of 46 (363460)
11-12-2006 7:45 PM
Reply to: Message 1 by 2ice_baked_taters
11-03-2006 12:08 AM


cells, unicellular and multicellular organisms
Unicellular organisms do not necessarily die in the sense that multicellular organisms do - they divide and become two new organisms, and when this happens the 'old' organism is gone but not dead.

Sometimes these organisms die (when resources are gone or habitat is lethal), but all the ones now alive are descendants of "split personalities" - the chemical contents have been changed to protect the innocent.

Likewise cells within multicellular organisms also divide, sometime they die, but all the cells within a living multicellular organism are descendants of "split personalities" of cells that make up that organism.

But it doesn't end there. When that multicellular organism dies there is still cellular life that has been passed from that organism to any offspring -- all multicellular organisms are descendants of "split personalities" of previous organisms.

There is no organism - according to the theory of common descent - that is not linked back in a continuous chain of "split personality" cells to the ur-life.

This is why abiogenesis is fundamentally different from evolution.

The only question then is why multicellular organisms are 'discarded' after a certain time.

It may be due to the strains of having to put up with all the other cells. The cost of repairs exceeds the budget for them.

It may have to do with sexual reproduction, where the eggs are produced in females at one time and then wait for the opportunity for fertilized life - but how long can a cell last without division to replace it? We know the age of the eggs affects the viablity of offspring.

It may also be a mechanism that controls the rate of mutations within a population so that new alleles are introduced in sufficient quantity to provide enough variation for natural selection events to allow some to pass.

Organisms don't evolve, their offspring are.

Food for thought?


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Taz
Member (Idle past 1365 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006


Message 15 of 46 (363493)
11-12-2006 11:24 PM
Reply to: Message 13 by Modulous
11-12-2006 4:51 PM


Re: immortality = more young not more old!
Modulous writes:

Careful. If we don't get older until older - there wouldn't be more old people around.


I wasn't using the word "old" in the sense that they are useless 3 legged beings. I used it to describe any generation that precedes the current for lack of a better word.

There'd be less old people around because more youthful people would die through predation/accident/murder/suicide etc.

And I was using it in context of how animal species consume natural resources. Please don't simply dismiss the contexts involved.

It is tempting to think of things from a human perspective, but we are a rare exception as far as animals dying of old age goes...

Again, going by context at the time, I wasn't talking about the current human population. I used "mommy and daddy" as a humorous gesture to describe a hypothetical animal species.

Mostly everyone else gets selected out of the gene pool much earlier

Which was exactly my point... if you bothered to look at the overall context.

But an organism doesn't care about its species.

Who said anything about caring or not?

As long as it doesn't adopt a strategy that is directly harmful to its environment (such as killing off all mates), an organism that has a long life gene will live longer and will produce more children which can also live longer (even if - in the long term - that would be harmful to the species).

The hypothetical species I was referring to had (1) very long lifespan, (2) produces at relatively the same rate as the average mammal, and (3) consumes relatively just as much resources as the typical mammal. If you want, you can replace the word mammal with any other classification, doesn't matter. Combination of regular breeding and long lifespan with regular consumption of resources is in itself a negative trait that should be weeded out due to limited space and resources.

It would be advantageous for genes to create beings that lasted as long as is physically possible to spread as many copies of themselves as possible.

Perhaps, but many species approach this with producing fewer but healthier offsprings that have more chances of survival.

Living longer means your alleles increase in frequency and as such it should be something that gets positively selected for.

Nope, not if a generation lives long enough to compete with the younger generations for the limited resources that are around, assuming resources and spaces are limited. Many species have solved this problem by killing off a great number of parent individuals right after mating season.

The puzzle then, is why don't we see such creatures?

We don't see such creatures because we don't want mommy and daddy (context) to compete with little Dan and Dan's little Robert.

Biology aside, even our economic system have clear examples of how the parent and grandparent generations make it hard for the younger generations to be successful. With recent economic downward sloping, many companies have stopped hiring newer, younger, fresh-out-of-college hot-shots. Why? People are living longer and healthier than previous generations due to better sanitations and medications. Because of it, the retirement age is now as high as ever before and there are talks of increasing the retirement age still. I know of computer science and programming majors that have had to resort to work as telemarketers while previous generation IT's sit comfortably in their secured jobs.

immortality = more young not more old!

I wasn't using the word "old" to mean useless three-legged humans. I used it to mean any generation individual that is older than the latest generation individual.


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The thread about this map can be found here.


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