Doubting Didymus

We would expect it to evolve? Surely that is a far cry from a foregone conclusion? Obviously, we don't immediately evolve every trait that would confer an advantage. We have to come by the mutation first, then it has to spread through the whole population without the individuals possessing it accidentally dying out in the meantime. Surely it's at least conceivable that the evolution of this particular trait is infrequent enough to be screened out by extinction, (always assuming that we are granting lobstrositys central points of theory for the sake of argument).

NZAmoeba

Okay, you're missing an integral part of being an atheist instead of a theist...

There does not need to be a why, or meaning, somethings things just ARE, and everything else happens to fall in place around that or die. Life was likely an accident brought on by the perfect conditions on our planet, and because those conditions have remained the same to continue to support that life, the life still exists. "Why" and "Meaning" are irrelevant, life is simply here, and it reproduces before death occours. As i said before, evolution doesn't care what happens to you after you breed.

ps. for anyone facing a xtian claiming that the planet is perfect as a reason for god existing, think about all the stars, billions of them, and think of all their planets, there must be trillions, by shear probability, there's gonna be a planet perfect for sustaining what we call life.

Albert Cipriani

Dear NZ,
You say: Fair enough. Since you are smart enough to realize the meaninglessness of meaning, perhaps you could explain why meaning isn’t meaningless to me. Or, more to the point, why do you bother even trying to make your meaning clear to us unenlightened blokes in this forum?

You are the atheistic equivalent of a Calvinist. Their theology can be summed up as: things are as they are because they are and there is nothing anyone can do about it cuz the bible says so, so there! How odd that tho you and Calvinists are poles apart, their fundamentalist anti-intellectual mindset could find a home in your icy outlook. – Sadly, Albert the Traditional Catholic

P.S. Peez, I'm loving your dialogue here. Don't get distracted by such distractions as this. I'll dispatch the snipers so that you can stay freed up to press the main battlegroups forward.

Deke

Albert, I too am enjoying Peez's dialogue - I trust that since my commentary is on topic, and in direct response to the original poster, malookiemaloo, you don't consider it a 'distraction'.

NZAmoeba writes to me: Okay, you're missing an integral part of being an atheist instead of a theist...

NZAmoeba, I didn't realize there is an Atheists manifesto ;-)

There does not need to be a why, or meaning, somethings things just ARE

I can accept this, but I personally remain interested to know, Why?

"Why" and "Meaning" are irrelevant

...and resistance is futile =)

As i said before, evolution doesn't care what happens to you after you breed.

This statement rules, I'm going to use it in a song I'm writing.

Jus' havin' some fun.

Enjoy,

Deke

NZAmoeba

Albert: If the meaning is there, its nice to know it. But sometimes there simply is none. things can and do happen without reason, or a predetermined purpose, and manage to hang around anyway.

and fine, call my outlook icy, if you need fairys and angels to make life worth living, so be it.

Deke: any belief or non-belief has some integral part, in the case of athiesim, its that there is no divine influence in anything.

And i will demand a royalty payment for your song, or sue for copyright infringement @_@

Peez

As I mentioned earlier, group selection can work, but it only appears to overpower individual selection under certain restrictive conditions. When I stated that we would expect populations to evolve in response to selection on individuals faster than metapopulations would in response to selection on populations, I meant that the conditions that would allow otherwise are very rare. One would need (to simplify somewhat) a population that "reproduced" faster than the individuals in it, and suffered higher "mortality" than the individuals in it. Such populations are theoretically possible, but I cannot think of any example.

To use a model as friendly as possible to the hypothesis that group selection has been responsible for the evolution of senescence (aging) as an adaptation, let us assume that we started with a population made up of individuals that already age (a curious assumption, but I am trying to favour the group-selection hypothesis as much as I reasonably can). Let us further assume that the evolution of senescence is limited by the availability of genetic variance (a weak assumption, as this rarely seems to be the case in real populations), and that the appearance of alleles that allow immortality (in the sense of no senescence) is very rare. Another few assumptions that would favour the above hypothesis are that there is no limit to the number of populations that can exist (a stupid assumption, frankly), and that there is no gene flow among populations (another stupid assumption), and that immortality has no costs at all (an assumption which is contradicted by the evidence, but perhaps there is some other mechanism of immortality that has no cost), and that immortal populations have the same chance as mortal populations of founding a new population (an assumption that seems to contradict the assumption that the population is less stable). Finally, let us assume that senescence does somehow reduce the rate of extinction of a population (a completely unsupported assumption).

For the sake of argument:

ten populations of about 10,000 blaps each exist
mortal blaps live one year, generations are discrete
there is a 1/10,000 chance of a mortal blap population going extinct every year
there is a 1/10,000 chance of any blap population founding a new population every year
there is a 1/1,000,000 chance that the immortality gene will appear in a population each year
there is a 1/100 chance of an immortal blap population going extinct every year

(obviously greatly simplified) What is likely to occur here? The number of populations should remain more or less steady. Eventually (after about 100,000 years) an immortal individual will be born in one of these populations. Natural selection will favour this immortality, and it eventually predominates in this population (for simplicity, after 1,000 years). That population will probably not found any new populations before it goes extinct, and even if it does the founded population would likely go extinct before founding another one: group selection would be more powerful than individual selection. I get the feeling that this is the sort of model that is being considered here.

Before going back to the assumptions, take a close look at the model and what one would expect to see. First, an immortal population evolves about once every 1,000,000 years, over about 1,000 years, and then goes extinct in about 100 years. This would mean that, at any given moment, there is a 1/1,000 chance that a given population would be evolving immortality, and a 1/10,000 chance that a population would be immortal. Is this what we see in nature? There are billions of populations of animals, but the vast majority are not studied. We would certainly expect, under this simplistic model, that millions of these populations might include immortal individuals, and hundreds of thousands would be entirely immortal. Another interesting effect is that each time an immortal population evolves, the overall number of populations going extinct goes up. The result is that the populations are going extinct faster than they are being produces, and the species ultimately goes extinct. This is easily mended by playing with founding rates and extinction rates, but it demonstrates how sensitive these models can be to assumptions.

So, as I have said before, group selection can work, but it requires restrictive conditions. I wish to revisit a few of those assumptions:

What if there is gene flow among populations? If new populations are being founded, there is almost certainly gene flow. What happens when mortal genes make it into an immortal population? Nothing, natural selection is against them. What happens when immortal genes make it into a mortal population? The population becomes immortal. Once immortality appears, it has about 1,000 years to spread to a new population from a mixed population, and another 100 years to do so from an immortal population. All it has to do is spread once in that time, and it will eventually take over. Changing the founding and extinction rates can compensate, but if genes are able to spread every 10 years or so (very reasonable) it would take some extreme assumptions to keep group selection ahead.

What if immortal populations have a greater chance to found new populations? If these populations rapidly expand, then there are more individuals available to found new populations, and they may have greater reason to (increased crowding in the current population). A founding rate of between 1/100 and 1/1,000 would allow an immortal population to persist, defeating the group selection described above.

Last, but definitely not least, what if immortality does not decrease the stability of a population? I have yet to see an explanation for why this might be so, and it is perhaps the most critical assumption of the group selection model presented. The obvious result of doing without this assumption is that eventually immortality would evolve in all the populations.

All this to say that senescence as an adaptation could, in principle, evolve by group selection, but it requires assumptions that are often restrictive, sometimes unsupported, and occasionally very unreasonable. On the other hand, it is very easy to see how senescence as a constraint could evolve by natural selection within populations.

Peez

Peez

Thanks

I am spending far too much time here.


Peez

SULPHUR

Sorry if I disturbed your thread. perhaps I can make amends by suggesting a site

http://www.cs.brandeis.edu/~richardw/symbiosis

the role of symbiosis in evolutionary adaption

Peez

Hi SULPHUR,

Thanks for the link. The article is interesting (though I did not read the whole thing), but it is a little fuzzy in parts. Note that it starts with "symbiosis" and changes to "mutualism" later on. I found the characterization of individual selection vs group selection a little simplistic, especially where he talks about altruism. This is perhaps because the author's background appears to be in computing and information. Sorry for dwelling on the negative, it is an interesting article and worth reading.

Peez

Albert Cipriani

Dear Peez,
I, too, suspect I'm spending too much time here. And I'm sure there's not a person reading this that isn't afflicted by the same nagging suspicion.

It's times such as these that we must recall the immortal lyrics of John Lennon. To whit: "Life is what happens while we're busy making other plans."

Since squandering our time here is not a part of any life plan, will not add one jot or title to our resumes, does not advance our career or evolution or even replicate us, it must be relegated to the ash heap of life itself. Ya gotta love them ashes. Here's to LIFE ITSELF! -- Albert the Traditional Catholic