Death, why?

[reverse]

In our case I don't thin you can really call it replacement; the two sets are distinct and differ greatly.

 

 

you got that right, the tooth fairy wont pay up on the second set.

 

ok here are some questions to help get to the core of this.

 

what creature lives the longest.

why.

what creature lives the shortest, why.

 

what person lives the longest why.

what person lived the shortest, why.

 

does sexual reproduction go hand in hand with shorter or longer life cycles.

 

do creatures that live longer depend on their parents longer.

 

at what point exactly does maturation become aging.

 

is there a connection between creature complexity and length of life.

 

Ps just read Darwin’s struggle for survival, he's a really good writer, subject matter aside

[Sayonara]

In most cases there's no simple answer for why one animal lives longer than another, because the life history of the species is shaped by dozens (if not hundreds) of factors over many generations.

[aguy2]

what creature lives the longest.

why.

what creature lives the shortest' date=' why.

[/quote']

 

Many mammalian lifetimes seem to be 'timed' to the number of heart beats. The hearts of a mouse and an elephant both beat about 1.5 billion times in an average lifetime. Humans though seem to be an exception, as at 70 years our heart will have beat about 2.5 billion times.

 

aguy2

[aguy2]

If nothing ever died naturally, ecology would be a hell of a lot more violent.

 

From the pov of the biomass as a whole the 'natural' death of individual organisms is a very good 'idea' for many reasons, but DNA/RNA molecules don't seem to have 'ideas' about the general good, they seem to be only 'motivated' by survival through replication. It seems to me that the 'I.D.' advocates are missing the boat by not trying to use internally preprogramed death as an indication of 'intelligent design'. I think they may be missing this due to their propensity to present the 'Creator' of the universe as some sort of 'goody-two-shoes' whose purpose in creating the universe is centered around the care, feeding, and 'testing' of hairless anthropoids.

 

aguy2

[Sorcerer]

Heres an argument.

 

1 All cells depend on the environment for their resources.

 

2 Resources are limited.

 

3 Populations have a carrying capacity (K), this is where the minimum ammount of resources/individual necessary for survival is reached.

 

4 Without resources cells cannot live forever.

 

C1 So, If cells lived forever, then K would be reached much quicker as the cells divide and do not die. (remember the parable of the rice on the chessboard)

 

5 K prevents the cell being immortal because 4

 

6 K also limits the individuals number of offspring and ensures instense intra-specific competition. Making it bad for the population as a whole.

 

C2 So, When K is reached any advantaged conveyed by immortality would be lost.

 

C3 Thus immortality is not a long-term advantageous adaption.

 

Remeber evolution is often a competition between populations and not just individuals, were there is altruism, symbiosis and a feed back in a food chain there is better survival.

[Sayonara]

Good argument (although with decreasing resources and increasing numbers of cells, there's an obvious adaptive solution.)

[Mokele]

C3 Thus immortality is not a long-term advantageous adaption.

 

But the long term is irrelevant. Selection works on the individual (usually), and even if there's a long-term disadvantage, a trait will increase in frequency if there's a short-term advantage, especially one that overbalances the long-term, species-level disadvantage.

 

However, I do think you're going in the right direction. I'd say, instead, that, once K is reached, the competition and other factors are so intense that non organism gets a chance to be immortal; they all die of predation or stravation or parasites or similar environmental insults in reasonable time. Immortality would require cellular machinery to maintain it, and mutations would occaisionally disable that machinery. If the lifespans of organisms with and without these hypothetical "immortality genes" aren't different due to the intense competition and high mortality rate, then "non-immortals" won't suffer any penalties. In fact, since they don't 'waste energy' on this maintenance, the 'non-immortals' might actually be at an advantage. Thus, the loss of the hypothetical cellular machinery for immortality would be selected for, and eventually such machinery would just disappear.

 

Mokele

[Sorcerer]

Good argument (although with decreasing resources and increasing numbers of cells, there's an obvious adaptive solution.)

 

Intra-specific predation or canabalism is a "hawk" strategy and as such isnt good for the populations genome as a whole, perhaps apotosis can be seen as the opposite, sarcrifice, or ultimate altruism.

[Sorcerer]

But the long term is irrelevant. Selection works on the individual (usually), and even if there's a long-term disadvantage, a trait will increase in frequency if there's a short-term advantage, especially one that overbalances the long-term, species-level disadvantage.

 

Yes and then the short term leads to the long term, there are a whole lot of immortals with this short term advantage competing for the same limited resources, they all occupy the same niche since they are all related and they are competing with their offspring, the short-term advantage leads to a long term disaster, any population with this strategy would be like a bacterial culture in a test tube, it would cycle through boom and crash, its like the hare that lost the race.

[Sorcerer]

I think they main point for this topic is that death hasn't evolved, imortality needs to evolve for things to be immortal, life can only work with what it has to evolve, and the chances of an immortal individual occuring is low, like any adaption I guess, but I doubt it would have happened, even if it has, my argument give reason as to why it wouldnt be advantageous.

[Mokele]

Yes, but the bacteria still go through boom and crash cycles, because it's beneficial on the short term. That's my point, the immediate advantage is what evolution works on, even if it has negative long-term consequences.

 

Say we have a population of organisms with limited resources, like the aforementioned bacteria. Due to natural variation, some bacteria are going to reproduce faster than others. These will become an increasingly large part of the population, as the population booms. Then it crashes. If there's no difference in mortality and simply a certain percentage die, the fast-reproducers will continually become a greater portion of the population, even though it accentuates the boom and bust cycle.

 

If one of the fast reproducers mutates to be a slow reproducer, which would dampen out the boom bust cycle, it'll be outcompeted because, while it's strategy is good for the whole, the others will still produce more offspring.

 

Similarly, if an even faster, super-reproducer mutant occurs, it would further accentuate the boom-bust cycle. But self-restrain doesn't pay in evolution; the super-reproducer would produce more offspring and eventually become the entire population.

 

What I'm saying is that evolution doesn't act on the long term, for-the-good-of-the-species level, it acts on the short term, who-can-have-more-kids level. This may produce diasterous results, as the example you supplied indicated, but self-restraint is self-defeating; those organisms that don't compete effectively on the short-term will never get a chance to influence the long term.

 

Mokele

[TimeTraveler]

Ok, I think alot of the people in this thread have misinterpreted evolution, there seems to be some underlying idea that genes can think and know what is the best option for their survival, this is not so, genes just "do" and when they happen upon the best option for survival this one wins out.

 

How and why do genes "just do"? What determines which is the best option?

[Sorcerer]

To mokele, perhaps with immortality the long term would be of consequence, short term pays off where the organism is mortal.

 

To Timetraveler, natural selection. The genes themselves have no idea what will be selected and what won't they aren't conscious and they cannot think or plan.

[Sayonara]

Intra-specific predation or canabalism is a "hawk" strategy and as such isnt good for the populations genome as a whole, perhaps apotosis can be seen as the opposite, sarcrifice, or ultimate altruism.

What makes you say it would be intra-specific?

[Sorcerer]

well, the imortal organism would be a genus, so any offspring that occupy different niches could be classes as different species, so I guess it would be inter-specific, Im not sure how long immortal life would last, K could be big for the earth.....

 

I guess u r onto something there, ok so my main reason why death is prominent then it that immortality hasnt occured through mutation so it hasnt had a chance to compete yet.

[Sorcerer]

Oh btw, your obvious solution is right, diversify in niches compete for different res. However it would rely on the immortal organism being able to adapt, I guess it has the time to K to produce diverse offspring......

 

Ok, sayo, what would be your reasoning as to why immortality hasnt evolved?

 

You got me thinking now its: It hasn't evolved because it hasn't evolved.

[Sayonara]

I was thinking we were talking about an entire biome that's immortal, since many resources affecting K for one species will affect K for species within the same community.

 

If we're just talking about one immortal genus, then I don't see why K should be any more of a problem than it is for your average mortal genus.

[Sayonara]

You got me thinking now its: It hasn't evolved because it hasn't evolved.

Ha.

 

My reasoning would be partly the same as yours (although with more specific conditions), and partly that immortal species would accumulate evolutionarily unfit genetic problems (even assuming a single immortal generation was responsible for all reproduction.)

[Mokele]

To mokele, perhaps with immortality the long term would be of consequence, short term pays off where the organism is mortal.

 

I'm not sure why it would be, though? I mean, regardless of how long a species lives, it's still got to compete on the short term, and that's where evolution takes place. I mean, if a new, mutant turtle (not necessarily a teenage ninja one) arises with half the lifespan of it's conspecifics, but with twice the reproductive sucess, it'll profit and become more common, eventually replacing the older form.

 

Perhaps populations or a species that hadn't yet evolved a particular short-term benefit might do better than other populations of the same species with that short-term benefit in species-level selection events (like famines or asteroid strikes), but any migration between populations would bring a superior short-term competitor in.

 

Mokele

[reverse]

How and why do genes "just do"? What determines which is the best option?

 

That my friend is a question best answered by Charles Darwin.

but basically, well adapted genes get to reproduce in some way more than less well adapted genes.

just like a sports team gets to the top of its league.

 

read Darwin’s original books , they are not at all dated.

 

tx boot.

[reverse]

Ok' date=' sayo, what would be your reasoning as to why immortality hasnt evolved?

 

[/quote']

 

may I but in,

 

it hasn't evolved because there is no niche to be exploited by evolving it.

 

you know, grow wings for the air, grow lungs for the land...grow immortality for...????

[reverse]

Just had a brain storm on this.

 

Why does the idea of immortality appeal to us?

 

Because we are genetically predisposed to try and survive.

And death is fairly final.

And scary.

And we are genetically predisposed to form relationships and despair when they cease.

 

So what on what levels do we attempt to survive?

The macro level,- where we fight disease.

The immediate level, - where we fight physical threat.

And the strategic level - where we plan for some future threat not yet present.

 

So what kind of evolution is “immortality”?

Possibly the last one, strategic.

I’m not sure if evolution does strategic enhancements.

[Sorcerer]

Ha.

 

My reasoning would be partly the same as yours (although with more specific conditions)' date=' and partly that immortal species would accumulate evolutionarily unfit genetic problems (even assuming a single immortal generation was responsible for all reproduction.)[/quote']

 

Perhaps immortality woul rely on multiple expression of genes for repairing DNA, and genes for making sure DNA repair was accurate, this way any somatic mutations would have plenty of backup. This still doesnt confront the problem of telomeres, these would need telomerase to restore cells after each division, I guess this could be possible without cancer.

 

Are there any bacteria that could be classed as effectively immortal, providing K isnt reached and no predation?

[Sorcerer]

Could it be true to call stem cells immortal.

[reverse]

Perhaps immortality woul rely on multiple expression of genes for repairing DNA, and genes for making sure DNA repair was accurate, this way any somatic mutations would have plenty of backup. This still doesnt confront the problem of telomeres?

 

you do this kind of thing with electronics and data checking.

to repair any lost or distorted data.

 

as for telomeres, if the parallel with electronics runs true, then you simply get the strand to skip the "check telomere then subtract one then activate" part of the programme.