All flora and fauna seem to practice it. So what's the point? What advantage is gained by dying? Neither do I understand what connection death has with reproduction. Why croak after fun-in-the-sun, as is so often the case?
Please try to limit your responses to evolutionary and / or biological reasons or speculations. I know all about the *sin* aspect.
Their is no advantage to dying for the individual and there is no connection between death and reproduction except for the fact that when an individual is out of the picture there are more of a limited number of resources made available to the survivors which may or may not enable them to reach their reproductive potential.
You imply that we somehow have any choice in death. We die because the very structures that allow us to exist in the first place are subject to degradation from interaction with the enviroment.
I didn't mean to imply a choice, sidelined. Sorry. I know we don't. But there would seem to be a huge evolutiuonary advantage to a creature that can patch itself back together as to one, as you say, is "subject to degradation from interaction with the environment."
As to the link between death and reproduction. It is the final act for many species. The mayfly, Pacific salmon and 17 year locust come to mind. So why give up the ghost when a species can remain alive and elbow out the competition for limited resources. It seems to me you give up any advantage by dying. Only a living plant or animal can be opportunistic.
quote:I didn't mean to imply a choice, sidelined. Sorry. I know we don't. But there would seem to be a huge evolutiuonary advantage to a creature that can patch itself back together as to one, as you say, is "subject to degradation from interaction with the environment."
There would also be a huge evolutionary advantage to a creature that could shoot laser beams from its eyes.
Evolution, like everything else, is bound by what is possible at any given point in time.
DNA replication is imperfect, but it has to happen whenever a cell divides. So every time a cell splits into 2 daughter cells, the daughters have a few tiny differences in their DNA. The copying and proofreading mechanisms are highly effective - the error rate is as low as one in 10 billion - but cells divide regularly throughout your life, so plenty of mistakes start to build up. Soon enough it makes a difference to your health and strength.
But families and species don't age, despite individuals doing so, because there is a method of periodically getting rid of unfavourable copying errors in DNA - sexual reproduction. Sperm and egg cells are produced in vast numbers, and then any which show the slightest sign of being substandard are killed. A very large proportion of newly fertilized embryos miscarry as a result of serious errors not caught at the sperm-or-egg stage, and that also keeps copying errors out of the surviving next generation.
Plants and animals which don't put any energy into looking after their offspring are dead ends, from the point of view of DNA replication, so there is no strong pressure for DNA replication to continue.
I don't think your DNA mutation rate depends on how much you sin - apart from smoking, of course
Death is eventually inevitable in all likelihood, due to predation, illness, accident, etc. So, mutations that confer short term advantages to reproductive fitness in exchange for problems in the distant future are a good deal, from a Darwinian perspective. On the other hand, a mutation that only pays off in the long run, with little effect early in life or a disadvantage in early life, are unlikely to become fixed in a population.
The collective effect of these short-sighted tradeoffs are "the aging process", or at least part of it.
This is all loose and speculative, but there is, I think, some support for this. I think. At the very least, it makes sense - I don't think you have to invent some fitness advantage for death.
The key aspect here is that while we are doing our level best to survive so is every other creature so while it is unlikely that we can,through evolution,"patch ourselves back together"if we never passed away then those who survive eventually replace all the other species as competitors foer limited resources.
Can you imagine 100,000,000,000 people on Earth.Damn, I don't know about you but I wouldn't want to be in the work force when that many people decide to retire to their pensions.
If I were to repost my orginal message, I should have asked what the evolutionary advantage is to AGING. I understand that this is genetically controlled to a certain degree. So, it would seem that those individuals that can poop AND get off the pot can bestow an evolutionary advantage to the suvivability of their offspring? Their species?
I seems to be making an intellecual connection between survivability through reproduction and death to get out of the way.
*Oh crap. Here come the theologians. Gotta go. Be back on Monday.*
I don't think there is an evolutionary advantage to aging; aging may be "genetically programmed", but only indirectly; see my first post in the thread. It's not that there are genes "for" aging, rather aging may be the side effect of genes "for" something else.
Aging isn't selected for; rather short term reproductive benefits are selected for regardless of the their cost later in life.
Better to reproduce like they vote in Chicago - early and often. Or, to paraphrase another cliche, Reproduce and be merry, for tomorrow we die of the plague, or are eaten by a lion.
I don't think this sort of explanation makes any evolutionary sense. In the phrasing of Dawkins, genes are "selfish". They're also "blind" - they can't look ahead. Either they work for the organism currently, or they don't work for the organism currently. There are no Darwinian (or other evolutionary) mechanisms that can look ahead and see that an organism's replacements will be better, thus the current individual should die off.
So, suppose an organism has an "Immortality" mutation, and survives predation, disease, accidents, and natural disasters to pass on the gene to many offspring. ASSUMING this has a large benefit (which it may not, if the species of organism in question tends to die due to one of the above causes anyway), then this should spread rapidly. One might imagine this could cause a population explosion.
So let's assume we have a situation where the immortality gene confers a large advantage, and the population gets huge. Now you have a big population, including many "Methusalah"s. Resources are scarce. Food is hard to come by, because a bajillion similar organisms are competing with each other. The older population isn't going to evolve - they have their immortality gene already. So forget about them.
What's going to happen to the youngsters born with a defective immortality gene? Is the lack of immortality going to confer any sort of reproductive advantage? On the time scale of their life, no. They'll tend to leave fewer offspring.
Even so, let's assume that some sub-group emerges without immortality, enough that the population decreases a little, and there is less competition.
This is good for the non-immortal offspring, right? Yes. Does it give them a competitive advantage? No! The immortal competition is benefitting from the reduced competition as well, PLUS they have the reproductive advantage of immortality!
I can't come up with any scenario which would select "for" aging and death. Rather, aging and death seem to be best explained as the side-products of other processes, not adaptations in and of themselves.
-Zhimbo, who suspects Syamsu will have a seizure if he reads this post.
[This message has been edited by Zhimbo, 10-25-2003]
Why do animals shed, because it is more efficient overall to replace an organ (i.e. skin) than it is to regenerate it.
The balance between the costs of regeneration and replacement are seen in engineering, as well as in living creatures. The lifespan of a creature is generally determined by the economics of this process given their particular structure and anatomy, and their lifecycle. Lifespans evolve to become longer, and shorter in evolution all the time.. but they never evolve to be indefinite. At some point, the cost, or opportunity cost, of regeneration always outways that of replacement.