Evolution question - why does everything die?

Factual Questions
1

What evolutionary benefit is there in dying? As I understand it, scientists are looking for the ‘aging’ gene (for all I know, they’ve found it.) I assume based on this that there is the possibility of altering the gene to stop the aging process. Immortality? Hardly… a number of diseases would probably claim lives at the same rate they do now, meaning that the number of people, animals, etc. living 200-300 years would be fairly small.

If the goal of all species is to multiply, why would every species have a pre-wired gene to terminate life? Is it to make sure that the species continue to evolve via new gene combinations? If this is true, and assuming the aging gene exists, I still don’t understand why eternal life didn’t evolve.

2

Individuals don’t adapt, populations do; a very long-lived species can be vulnerable to changes in environment that a population of short-lived individuals could cope with by adaptation (albeit losing less-suitable individuals along the way).

3

Also individuals of a long-lived species would be in competition with their own offspring.

4

So what? then, life goes into “survival of the fittest” mode, and whoever wins can stick around. It would make more sense that life would benefit by this. If you have a kick-ass lion that is 150 years old and can still maintain his alpha male status, so be it. Those are genes that the species would only benefit from.

5

I’ve heard it said that we die so as not to compete with offspring as they reproduce.

Another line of though which also answers the question is that we die because:
A) we are hit by a bus
-or-
B) our genes have a tail of sorts, each time genes divide that tail shortens till it’s no longer divisable. When It’s no longer divisable that gene will refuse to divide and the cell will eventually die.

6

In general, most organisms will die through accident or violence long before the effects of any “longevity genes” (were such to exist) can be felt. Similarly, genes with harmful effects which are expressed late in life will be less likely to be selected against, and so will likely remain within the population (this is generally known as the mutation accumulation hypothesis: negative, late-life mutations will tend to accumulate because in most instances, the individual will die before they are expressed anyway).

An alternate theory is the antagonistic pleiotropy hypothesis, wherein it is belived that certain genes which bestow greater survival/reproductive advantage early in life tend to produce detrimental effects late in life. Since early reproduction is more advantageous than late reproduction, such genes will be favored by natural selection.

7

its HARD to build something that lasts for more than 30 years or so, especially when all you have to work with is bits of squishy water. Its not that evolution is specifically selecting against old age, its just that you rapidly run into diminishing returns the longer you want an organism to live.

8

  1. If an organism reproduces before dying then that death is evolutionarily neutral. The genes have already been passed on.

  2. If an organism dies before reproducing the death will ordinarily be from one of two causes:

2a) Death from bacterial or viral disease or infection. Such a death prevents the passing on of genes that produce an inmune system that won’t counter such disease or infection.

2b) Death from accident or predation. Accidents just happen and might or might not be evolutionarily significant and I can’t think fast enough to come up with a good answer to this one. Death by predation prevents the passing on of genes that produce an organism that can’t avoid a predator.

9

I think that’s looking at it from the wrong end.

What are the benefits from keeping individuals alive after the genes have been spreaded out?

10

… and having dominated the pride (and as a result starved all or most of his offspring to death during a particularly dry summer), he treads on a thorn and dies of septacaemia, and has not passed on his longevity genes.

11

Because.

It just is.

12

Mangetout, why would one long lived lion be able to starve an entire pride of lions?

anyway…

ok… There may be a reason as to why life dies. If you take the premise that an organism can never be perfectly adapted, then you MUST have new mutated organisms for the chance to develop a better organism. If the original organisms stayed around they would be impeding the new organisms survival. ‘Then wouldn’t survival of the fittest come in?’ well this is a poor argument in this context seeing as though younger generations are often weaker and need to develop and grow while the older generations are already fully developed and established in their behaviour and potential strength.

But. The good thing is, we as humans ARE NOT PERFECT but have learnt how to bend the rules. We can alter the genetic structure of our next generation directly. And just in time too, because of modern medicines and our communal system where people get fed and can breed (not based on adaption attributes like intelligence or strength, but based on geographical location, i.e. Australians don’t die of starvation and everyone eventually gets a root, where as Ethiopians die of starvation and everyone roots too much) it is no longer survival of the fittest. Stupid, ugly, weak humans can survive in society and can breed with other stupid, ugly weak humans to create yet another generation of ffuglies, or Stupid, weak humans can breed with Intelligent, strong humans and dilute the attributes of the next generation. Inferior adaptations are not being ‘killed off’ like in the animal kingdom, they are infecting our entire population completely nulling all evolution of the human species.

Now back to how we can change our genes… Its about time, and except for a few religious fanatics and a couple of ethnic know-it-alls we’ll be back on the path of evolution in no time. By altering the genetic structure of new generations we can create humans that are immune to certain diseases, are more intelligent, (maybe even better looking), and stronger. These attributes are what should have been adapted if we had of let our weak die, now we can make them happen with our skill of dna manipulation.

Obviously in a system where evolution doesn’t work, i.e. our current species, or a species that can better itself artificially, then it would be alright to allow organisms to never die. Thus, although genetically inferior, older generations can co-exist with superior generations in an artificial environment such as the one we are able to create with technology today (civilisation, i.e. cities, agriculture, etc).

13

A lion is perhaps a bad example.

14

lol

15

No it’s not, not at all. Let’s just extend it further.

**What’s the point of breeding then? part I:**Let’s say this bad ass lion has been breeding for 200 years and a generation for lions is approximately five years (time to reach breeding age plus a year or two.) This lion will have been breeding for 40 generations and produce an ugodly number or grandkids, nieces, nephews, etc that is? Eventually the lion’s DNA saturates the pride because of the huge amount that has been thrown into the gene pool the last two hundred years. The pride experiences a loss of genetic diversity, and is thus less likely to survive an unforseen disaster. The fact the 200 year old alpha male has inbred with every generation of his offspring isn’t going to help either.

This could be a very real problem if species did not age. The lion would never have to give up his alpha male status to a younger, stronger lion. Over a few tens of generations the pride has experienced so much inbreeding that there is a drastic increase in the amount of birth defects and every viable offspring is vulnerable to pathogens because of a lack of genetic diversity.

But most of the original lions are still around and are not as vulnerable to the same pathogens as the newer generations. If the newer generations just keep dying, what’s the point of breeding? That’s what the whole thing boils down to really.

What’s the point of breeding then? part II: If there is no death then there is very little reason to breed. More important than the decrease in genetic diversity hypothesized in part I is the fact that the environment cannot sustain the growth and all the lions will starve to death if they keep breeding. There simply aren’t enough antelope to feed a geometrically expanding population of lions. The lions may even develop a behavioral adaptation of killing their own offspring to reduce the population.

Evolution, for all intents and purposes, stops. We know from the fossil record that every species is eventually killed off by something. The only way the genes can insure their continued existence is to allow the species they code for to spin off a different species.

Evolution is immortality.

16

As a side note: There are organisms that don’t “age” per say.

The giant redwood tree never “get old”. They continue to grow their entire life. The are finally killed by their own size. They are crushed by their own immense weight.

There are other odd examples about here and there.

17

Why does everything die? Because it’s impossible to make anything live forever. The issue isn’t evolutionary, but rather physical/biological.

No matter what kind of organism, sooner or later it will get caught and eaten, or food will run out, or a safe will fall on its head, or something else will happen. Some organisms are larger and more adaptable and can expect to survive for tens or even hundreds of years (for turtles and trees); some organisms have an expected life span of a few hours. So by a bacteria’s standards, you DO live forever.

The reason organisms aren’t immortal isn’t because of some selective disadvantage to competing with your own offspring (trees for instance DO compete with many of their offspring, and the offspring will generally lose the battle, too, until the parent is hit by lightning, blown over by a hurricane or something). Organisms are not immortal because there’s no combination of possible genes that could make an organism immortal. (If anyone has a gene that confers immunity to a safe falling on your head, let me know, please!)

Now, given that sh*t happens, and every organism will eventually get knocked of by some random event, it is true that there’s little selective pressure for genes that benefit an organism only after it’s expected to have already been run over by a bus. And if those genes have a disadvantage when younger, there’s a big selective pressure against them.

For instance, it is conceivable that an animal could develop that regrew its heart and other major organs at regular intervals. This would clearly add to the animal’s lifespan, as damage and long-term wear and tear on the organs would be repaired. But that would mean they’d need two of every organ, so one would work while the other regrew, and that would be a big investment of energy and mass. So some one-shot animal would easily out-compete them and they’d be eaten or starve long before they had a chance to regrow a heart .

18

From what I’ve read the “tail” is composed of junk DNA strands called telomeres. Each time a cell divides and DNA is copied, some telomeres fall off. However, since they are useless DNA to begin with, it doesn’t damage the cell. Once the last of them are gone, our DNA still gets copied, but the necessary strands start to fall off, which causes damage, which can in turn cause aging.

19

The question that isn’t being asked here is: does everything actually die? When a bacterium divides, does it die? I would argue that bacteria don’t die, at least not of old age, and are effectively immortal. A lot of, if not all, single-celled organisms could probably be considered immortal as well. You might as well throw in certain fungi, algae and plants as well. Barring accident or predation, individuals of these species could live forever.

20

I’ve wondered about that myself. Perhaps some of the bacterium do die, even after splitting. Thus they would continue and die at the same time.

Of course, in a broad sense, the same argument could be made about us. We live on when the sperm from one person and egg from another combine and cause our genetic characteristics to continue, albeit in a new combination.