quote:So, suppose an organism has an "Immortality" mutation, and survives predation, disease, accidents, and natural disasters to pass on the gene to many offspring.
Here is where the "laser beam eyes" comment comes into play. It's pretty unrealistic from an engineering standpoint to propose a complex system which works perfectly forever. Hypothetically, we can propose anything we want, but the rules of reality come into play in this particular instance.
The longer an organism lives, the more of it "wears out", requiring additional regenerative components to fix them, which also cause the organism to become more complex and more prone to problems. Etc. etc. These regenerative systems also have to evolve, but they have to compete with the replacement system of death and birth, which already seems to work really well.
What this means is that with a non hypothetical organism.. at some point it's just easier to start over from scratch every generation.
[This message has been edited by Rationalist, 10-25-2003]
Didn't a Dr Carrel win a nobel prize for demonstrating that "The cell is immortal. It is merely the fluid in which it floats which degenerates. Renew this fluid at intervals, give the cell something upon which to feed and, so far as we know, the pulsation of life may go on forever."?
The explanations that I read is that aging is just that the rejuvenation/repair mechanisms aren't perfectly efficient and so the "wear" builds up, causing aging. If, because of disease (caused by parasites) and predators, most of the individuals in a certain population are dead by 45 years old, there is no evolutionary advantage to develope repair mechanisms that will keep a body in perfect health past 45.
The first is trivial, while the second is the really interesting issue. Why organism-scale senescence? Why not perpetual good health?
Part of it is lack of indesctructibility on the cellular level; successful self-repair may require cells to commit to performing it, such as plant meristem and cambium cells and animal stem cells. Trees can live hundreds of years, but they are really thin growing layers that produce lots of dead material -- wood, bark, and dead leaves.
Another cause is lack of selection for survival after having successfully reproduced. Plants often "go to seed" and die soon after producing their seeds; a phenomenon also common in the animal kingdom. This can happen for two causes: lack of selection for continued survival and avoidance of competition with one's offspring. The latter mechanism is suggested by what looks like suicide mechanisms: male Antechinus marsupial mice will die soon after copulating with their mates, having produced lots of stress hormones.
Also, inability to survive harsh conditions may provoke senescence; in temperate climates, many plants do not try to survive the winters; gardeners know them as annual plants. Their seeds can survive, and that's what keeps such plant species going.
Hi sidelined, I don't think you can disconnect death from reproduction. Natural selection will favor genes that enhance fitness i.e. ability to reproduce even at the expense of longevity. A lot of the developmental process (not to mention reproduction itself) is costly in terms of oxygen radical production and other chemical byproducts that are toxic. Over time this will be harmful to th organism. In experiments with C. elegans where the sex cells are ablated early in development, there is an average increase in lifespan (going from memory it was almost as large as calory restirction i.e. 30% increase). Eunuchs tend to live as long as women. All in all there is a high cost of reproduction which ultimately leads to death.
There were really only two possible strategies for life (with a lot of variation allowed for one of the two).
First, the first or close to the first replicators are indestructable, no real selection for reproduction, no real logic for replicators either. Basically an immortal population.
Second, replicators survive by copying themselves...a nice tautology but the original replicators could only insure their survival by producing more copies of themselves which is a process that continues to this very second. The strategy insures that more replicators are produced without any safeguards to protect the original replicator. The same way my children would carry (some) of my genes but I will die..yet, my DNA has passed to the next generation.
The thread title is a bit strange. What would be the advantage without death? Immortal reproducing organisms? What biosphere could support such a population? You either have organisms that don't die and don't reproduce, or organisms with an expiration date and a hereditary mechanism.
"The thread title is a bit strange. What would be the advantage without death?"
Yes, I agree. The topic title is a bit Off Topic. After reviewing replies, I realized that I was really asking about aging. Recent medical advances have certainly thrown a wrench into the whole "death with dignity" schtick. I must conclude from all I've read that biological death goes with the territory and that's how it should be.
I look at all the attempts to allow people to live into their hundreds and then look at pictures of Bob Hope and George Burns in their final days. Either they were well pickled or had a formaldehyde gene that I was unaware of. In either case, I say "No thanks. Let Nature takes it's course."
Thanks to all for excellent posts. More fun than graduate school and infinitely cheaper.
I understand evolution's explanation for death and aging, but I still have a question:
Evolution is all about natural selection and beneficial mutations and ADAPTING the environment, correct? Well, knowing this, I would think that SOME animal would be able to adapt to its environment to the point where it could survive a little longer than all animals today. Plants seem to have been somewhat successful (assuming evolution is true); some trees live to be close to a thousand years old. The oldest an animal can live, though, is about 150 years (the box turtle), and that is a bit of an anomaly. The vast majority of animals do not live longer than a year, and most mammals do not live past about thirty years. At least that's what I learned. Can somebody explain, please? I'm not attacking the ToE, I'm just curious. Thanks.
Evolution is all about natural selection and beneficial mutations and ADAPTING the environment, correct? Well, knowing this, I would think that SOME animal would be able to adapt to its environment to the point where it could survive a little longer than all animals today.
Ok, sure. Suppose it did. What would be the survival advantage to its offspring? There has to be one for its longevity genes to spread throughout the population.
Evolution doesn't optimize. I don't have to outrun the bear. I just have to outrun you.
Guess what, the advantange (not in the sense of age (except relative to born with the appearence of age) ( we dont know yet how to discriminate Croizat's age of a species from age of a process in the species "The AGE OF A SPECIES is yet something which the AGE OF A PROCESS OF SPECIATION is not." Principia Botanica p 1474 (yes that IS the correct page #) as of yet so please dont do-a-RANDY on me)) is that infinity finds it's finite reality no matter the catastrophe and I believe a selection of genotype or phenotype will produce a TELIC characterization (once Gould's Big Apple is completely cored) and proove the difference (g-p) never existed but was rejected (the conclusion I would have reached by then) as it will be, I predict, an actual infinity instead whose potential was obscured in the biometric vs mendelic conflagration of the duality BETWEEN Newtonianism and Cartesianism ( a track can extend a length but a length is not seperated from a REARRANGABLE association of propositions programmatically) absolutely. The dark nursurey of evolution is very dark indeed.
quote:And how can your question be, in any way at all, be taken as "attacking the ToE"?
I was simply asking a question and not making some weak attempt at trying to disprove something. I have encountered people before who took something like my post as such and suddenly became very angry and/or insulting when I was just trying to learn a little more.
quote:Your question is why doesn't any animal live a little longer than any today? Why should they?
According to the ToE, animals adapt to their environment. It just seemed to me that some animal would adapt to the point where they would live a little longer than most do now. I understand that older, aged animals have a hard time surviving and can be burdensome to the rest of the species, but if a mutation allowed an animal to extend its "prime" by several years, I don't see why this feature would disappear (except for overpopulation). Whatever, maybe its just me. Choose to ignore my question if you wish.
but if a mutation allowed an animal to extend its "prime" by several years, I don't see why this feature would disappear (except for overpopulation).
Well, that's it, for one thing. You have to assume that every population is at K (maximum capacity) or, if it isn't, eventually will be. Ergo there's always competition for resources between individuals.
How does an animal with greater longetivity provide a survival advantage to its mature offspring? Especially if it's competing with resources with its offspring?
You've mentioned a few organisms with great longetivity, like trees, for instance. Trees can afford to live so long because they have a lot of mechanisms for making sure they don't compete with their offspring for soil and light. Some, like fruiting trees, get other animals to cart their seeds far away. Others, like some pines, have seeds that won't sprout until there's a good chance the parent is already dead through forest fires.
Sea turtles swim for miles and miles to lay eggs, and abandon them.
There's no selection pressure for longetivity. In fact in the absence of a really good spreading mechanism, longetivity of the parent can select against their offspring, because they compete for resources.