Wounded King

When Fred Hoyle said that the evolution of the horse was a result of improved nutrition, I assume by this you mean that an improved source of food became available for some reason such as migration or invasion by a new grass, he may have been partly right, but that is hardly likely to be the whole story.

gcameron

Well, at least more of us are reaching our allotted threescore-and-ten than in Biblical days, I should hope.

Doubting Didymus

Hullo there lobstrosity. Good to see you back.

This is a little confusing for me. Are you talking about some variety of species selection? Surely organisms within your postulated steadystate population, who possess a trait that influences them to break that trend by living a longer span and producing offspring constantly would be favoured, just by the action of standard run-o-the-mill natural selection, and become increasingly common? What is going to stop them?

Another query: do you actually know of any species that have found adaptations that smooth their population cycles? All the species I know of follow the usual exponential peak/ sharp drop pattern, in tandem with the same patterns in the species they share ecological relationships with. Obviously some species have smoother cycles than others, but is that due to actual adaptations?

Doubting Didymus

I've had a small thought.

Most of us know the story of why sexual recombination is beneficial, though counterintuitive, right? The idea is that having variation in the generations protects from certain disasters, but also that the ability to recombine beneficial mutations, (such that an organism can eventually be born in posession of multiple beneficial mutations that each have their origin in separate ancestors), is a feature that outstrips asexual counterparts.

Forgive the diversion, where the heck was I? Oh, right yes. <ahem>.

Given that recombination from generation to generation is such an advantage, enough to play a part in the evolution of sex, is the hypothetical immortal population at a disadvantage? If you have a given combination of traits set under glass for a very long time, as opposed to being a temporary crystallisation, is the recombination factor going to stagnate more than the sister species, in which the important traits never stand still?

LHP Adept

While many here have responded sagaciously to the O.P., I would like to add a couple of things.
To illustrate my point, I will use a hypothetical animal, the Wyzix. Imagine that there are two varieties of Wyzix living in identical forests, one long-lived (does not lose fitness with age unless it is injured or develops a chronic illness), and one short-lived (grows old and dies). In addition to the boom-and-bust effect due to limited food resources, there will be other factors which favor the short-lived variety.
If the long-lived variety is to have a stable population (to avoid crippling boom-bust cycles), it must have a lower birthrate than the short-lived Wyzix.
Mutations occur at random. Most changes are for the worse, and don't get propagated. Neutral changes may be propagated, but usually not to the point of becoming general in the population.
Changes which make it easier to survive and reproduce IN THE SPECIFIC ENVIRONMENT in which the population lives, will tend to become more common with each generation, eventually becoming the norm for the population.
Evolution is the accumulation of those 'positive' changes. The more mutations occur, the more 'good' mutations occur. If the short-lived Wyzix lives ~10 years and the long-lived variety live ~40 years (before being eaten, drowning, falling off a cliff, etc.) and each produces a similar number of offspring during its lifetime, the short-lived Wyzix will have ~4 times as many mutations. The 'bad' ones don't matter, they just die and don't affect the population. 4x as many 'good' mutations means that when there is a calamity, such as a severe winter, drought, habitat invaded by a new species, etc., there will be more variety in the short-lived population, and a better chance that some individuals will have whatever it takes to survive (thicker fur, wanderlust, ability to digest an alternate food, etc.). Over time, the short-lived variety is more likely to survive calamities which may cause the extinction of the long-lived variety. The quicker generations mean quicker evolution.
Also, predators and their prey sometimes engage in an evolutionary 'arms race'. The prey evolves some trait to help it avoid detection, detect danger, run faster, etc. and the predator must evolve a response. A faster-evolving species has an advantage here, too.

Albert Cipriani

Dear Gcameron,
You said: No implication about it. It’s a fact, Jack. Just as there is no doubt that one comes before two, all of the original single-celled life forms were (as they still are) immortal.

Only when evolution hit upon the new and “improved” versions of life that were multi-celled with some of those cells being perverted into nasty sex cells did they lose their immortality. This idea is captured in the biblical story of Adam and Eve who lost their immortality through sin. (The wages of sin is death.)

And because you didn’t know this, for your punishment I will now inflict upon you one of my sonnets on topic. – Cheers, Albert the Traditional Catholic


The amoebae is immortal. . . If death occurs, it comes only through accident. -- Biology, Elliot & Ray, Appleton-Century-Crofts

ODE TO AN AMOEBAE
In the beginning, all life was a formless mass;
it hovered in the waters, pimpled the face of the deep.
This caldron of change, encircled by a sky of brass,
spilled over onto earth of iron, there to creep
to wing or walk; these bubbles of life's ferment pass
on down the gullet of their harvests, while you reap
yourself and do not have to sow nor need to sleep.

You endless eddying amidst this world of flux.
You protoplasmic patch off the original
unaltered fabric all life 's patterned after, crux
of brains and bodies, spinning your continual
life's thread out of your spindle fibers, time conducts
you in immortal lines. O could your vacuole
speak of the Word that was, and was responsible.

Doubting Didymus

Bravo! I particularly like the final line.

Wounded King

Single celled organisms obviously arent immortal, if they were then antibiotics would be singularly unsuccessful.

But even that aside it is arguable whether either of the daughter cells produced by asexual reproduction is still the original parent cell.

Jack the Bodiless

I think LHP Adept has a good theory there, it's close to what I was about to suggest.

Given finite food supply in a region, it seems rather obvious that once a population has built up to the limit allowed by those resources, then a population of short-lived critters will have a younger average age than a population of long-lived critters would. They'd be reproducing more often, and hence evolving faster.

In this scenario, given the competition, any strategy that the long-lifers use to stay alive will inevitably work against the immediate interests of the youngsters, who represent the "cutting edge" of evolution for the species. Likewise, any ailment or condition which causes the oldsters to suddenly drop dead will benefit the youngsters, and can be selected for. It would be a very sluggish selection process, because the "termination trait" isn't directly beneficial to individuals within the group who have it: it's useful only to the group as a whole.

Peez

I would like to respond to a few comments, which I have selected, in the hopes of clarifying a few points.This scenario does not fit with what we understand about evolutionary processes. Natural selection tends to favour individual reproductive success, even at the expense of the population or species. That does not mean that traits which improve a population's chances for survival are necessarily selected against, but there is generally no reason to suppose that they would be selected for. It might be possible for group selection to favour individual traits that promote group success, but without restrictive conditions (e.g. groups with shorter "lifespans" and greater "reproductive rates" than individuals) natural selection on individuals is more powerful.I don't see this as evidence that "death is an evolved property of life." Even if the telomere hypothesis is one of the causes of aging (it looks very much like it is a contributing factor), it would only be a mechanism of aging and not any sort of evidence that aging has evolved.Why would we evolve that way?Death is not required for reproduction.This suggests a misunderstanding of how evolution works. If I may quote Evolutionary Biology, Third Edition (Douglas J. Futuyma, 1998, Sinauer) p. 350-351:Natural selection favours individual fitness, not population of species survival.See below.If one looks at it simplistically, there does not seem to be any reason to expect that aging and reproductive rate would be correlated. However, biological systems are not simple. It is very easy to imagine that cells that will last longer might require more time, energy, and other resources to build. This would slow growth, increasing the chances of being killed before reproducing and directly decreasing reproductive rate by increasing generation time. It would also divert resources from the reproductive system, thereby reducing reproductive rate further.

Nevertheless, we do not need to rely on such hypotheses, however reasonable. It is important to realize that genes work through specific processes of transcription and translation, and through the actions of proteins in development and throughout the life of the organism. As Futuyma explains on p. 568 of the same text, genes that are favoured by natural selection because they increase reproductive rate early in life even when they also result in decreased longevity (citing experiments by Rose and Charlesworth, 1981, and several others).It is interesting that you called Nic for making a statement "as if it's a fact that doesn't even require justification" but provide no justification here. I certainly do not agree that "it appears evolution has modified animals to actually have degradation with age."Do you have a reference for this? Of course it would not demonstrate that death has evolved, note that we already know that unicellular organisms do not age the way that we do. Interestingly, I believe that there is a line of human cancer cells that has been dividing for decades without any signs of aging (from Henrietta Lack).I have already explained why this is false. Natural selection favours individuals that reproduce faster, even if this drives the population (and species) extinct.Do you have a reference for this? In fact, size and lifespan tend to be correlated, so all three are correlated together. If an organism is larger it takes longer to grow to maturity. Since it cannot reproduce before then, this increases generation time and therefore slows reproductive rate. Once reaching maturity, larger organisms generally reproduce more slowly (compare mites and roundworms to gulls and whales), though there are exceptions such as maple trees which maintain a high reproductive rate (and which do not age much).[/b][/quote]I think your argument might explain things to a zeroth-order approximation, but I would not expect such an approximation to be very good.[/b][/quote]Do you have a basis for this?Could you provide a few examples, I cannot think of any off hand.You have failed to establish any evolutionary advantage to longevity (though I can actually think of at least one). Of course the point is not "is there any conceivable evolutionary advantage to increased longevity?", it is "given the constraints present, is there any evolutionary advantage to increased longevity?"Yuck!O.K., that is a good description of evolution, but I do not agree with the line before "Yuck!" Given that you seem to have such a good understanding of evolution, why are you making such odd comments about the evolution of traits that are good for the species?It would be more correct to state that adaptation is the most obvious result of evolution, however there is a great deal of genetic drift that does not bear on adaptation.

Peez