|Apr3-10, 11:09 AM||#35|
|Apr3-10, 11:11 AM||#36|
Sorry i was viewing the 2nd page again and again; didnt notice your post.
But can you exactly pinpoint where i have gone wrong in my argument (the X-Y scenario and the analogy derived for humans)? so i can correct myself. Thanks.
|Apr3-10, 11:13 AM||#37|
It truly is NOT random, it just HAPPENS naturally.
There is no CHANCE involved in natural selection. It is either you reproduce or you don't and it is assumed that those who have the opportunity to reproduce were BETTER SUITED for mating in an ENTIRE POPULATION. Why? Because they DID reproduce. This means that THEIR genes are inherited, rinse and repeat. Sure in HINDSIGHT you can say 'oh it was shear luck that this organism with this gene mated with this one and had x children with said gene' but it WAS NOT LUCK. IT WAS NATURE. Over time these changes can be seen and THAT is what is called evolution. There is no dice rolling in this to decide who mates and who doesn't.
Mind you this is quite a dumbed-down version.
|Apr3-10, 12:16 PM||#38|
Chance is critical in the theory of evolution, and specifically in population genetics. For example, you can give probabilities for a particular mutation to become fixed or eliminated in a population. There's a definite and quite substantial, in fact, chance that a beneficial mutation will be eliminated. That's because natural selection is about amplifying the small changes in probabilities that arise in all the random chances of life for an individual with a given mutation.
For example, have a look at Population genetics: a concise guide, by John H. Gillespie (2004). I found that reference just with a quick google because I knew pretty much any basic reference would tell the same story. Note that there's an appendix on probability. It's essential to figuring out how evolution works.
Another important feature of evolution is called "genetic drift". This is basically change which has negligible consequences for an organism, so there's no natural selection involved. It's still evolution, by biological definitions.
A really good resource for learning more about evolutionary theory is the talkorigins archive. A sample article there is Random Genetic Drift , by Professor Larry Moran. This is a website intended to give basic information for interested readers; and I think it is an excellent starting point. Full disclosure; I've long been involved personally in talkorigins, which is current moribund after a hack attempt probably from creationists. (They really don't like it.) But I think it will be back up and working again sometime soon with a whole pile of new features.
So I disagree. Evolution truly IS random. But random is not the same as a coin flip. Evolution works its wonders by biasing the dice. And it is amazing what you can achieve with a small bias in a random chances of life. I'm also an ex-blackjack card counter. I was able to get maybe a 1% edge over the casino until I was caught and banned and had to find another hobby. Was it random. Sure. But will the casino always make money? Sure. They make sure they have the edge, and that's all they need.
Cheers -- sylas
PS. Your caps lock key seems to be sticking.
PPS. I'm using the conventional biological definition of evolution as any change in the distributions of heritable characteristics within a population over time.
|Apr3-10, 01:02 PM||#39|
Only in hindsight can we look back and say 'well it's lucky that humans evolved larger brains when they could have just as easily stayed with more primative brains,' the thing is though that it was not by chance but by natural selection and other mechanisms which I don't feel like getting into in this particular thread.
|Apr3-10, 01:06 PM||#40|
Chance- luck: an unknown and unpredictable phenomenon that causes an event to result one way rather than another
Evolution- (biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms
change in the inherited traits of a population of organisms through successive generations
Both meaning the same thing. Of course randomness has effects on Evolution but that is far from being the same as saying Evolution is random. Period.
|Apr3-10, 01:22 PM||#41|
Thanks for the call.
>I have to disagree with what you have posted.<
“No cow is like a horse.
No horse is like a cow.
That’s one similarity anyhow.”
So we can be equally comfortable in the closeness of our agreement. Now…
>Genetic variation is possibly the only 'random' event that leads to evolution...<
Not at all very possibly! For one thing, I rather fancy I pointed out the contingent nature of randomness, though I did not spell it out because it is an old topic. Consider: suppose I were to give you this string of digits to evaluate for randomness: 5517027618386062613313845 Perhaps you say: Ahah! It fails the test in such and such an attribute. Then I say: try this one: 7245870066063155881748815. You react in much the same way. OK, I say, you don’t think much of my random number generator, but let’s see you correlate the two. In fact, lets see you correlate a mathematically large expansion of those digits with any other sequence that is mathematically independent of them.
So far so trivial, but it leaves one of us with the problem of how one is to decide whether the numbers are random or not. Even if you do not fail to correlate either of the sequences with some function each, unless you can predict how the next digit of one sequence will correlate with the corresponding digit of the other without calculating both of these first, how can you say that they are not random relative to each other?
Now, as you have noticed, these two sample strings are in fact from highly non-random sequences, in the sense that they can be generated to arbitrary lengths by fairly short programs. In fact programming courses often include their generation as demonstration exercises. One comes from pi and the other from e. From another point of view however, they are highly random. From what external criterion that does has no isomorphism with either of them, would you undertake to predict their next digit, much less the mod 10 difference between the two?
What, you might ask in rebuttal, does that have to do with randomness in evolution? In particular what does it have to do with randomness other than in genetic variation in evolution?
Well, firstly, just how random is genetic variation? Not really very. There are all kinds of biases and constraints that make certain mutations likelier than others, and what is more, make the effect of certain mutations more relevant than others. To put it another way, we might not easily predict the next effective mutation, but we would hate to use spontaneous genetic change as a random number generator!
So genetic change is not as random as we might like, not as mathematicians or computer scientists anyway. But as biologists we might well argue that it is random enough for jazz. However, what about the other variables? What other variables are there? The first thing to bear in mind is that we are customarily very loose in our use of terms like “evolution”. Usually people say “evolution” when they mean “Darwinism” which is more like the effect on a population, of natural selection. Evolution, as I am sure you realise, is something more like the more or less systematic change of a population’s gene pool (the relative frequencies of given genetic attributes from generation to generation, if you like). But what is natural selection? It is (correct me by all means!) the relative frequency of successful reproduction of organisms of distinct heritably determined phenotypes in given ecological circumstances. A little more indirectly (or directly, if your name happens to be Richard) this translates into selection for given genetic attributes.
Well now, what can we do about predicting the nature of our ecology? Is it random? Is it??? If so, with respect to what? The genomes of the population? You might have some trouble denying that one! Let’s see you justify your prediction of the correlation between whether our wolf cub gets poisoned by a touch of botulism in carrion, or starvation because there is no carrion. Or by a bear because he cannot fit into a hole when his smaller sibling can. Or a snakebite because with his superior speed and strength he got to the snake first? Is all that so very predictable? And if not, how do you make it out to be less random than genetic change? And if it is, how do you correlate it with genetic change?
Let’s change the subject and move on to sentence 2.
>...however genetic variation in single organisms is not evolution. <
***Really?*** We learn something new every day! Firstly, I assume that what you mean is that genetic variation between the organism and its parent(s) is not evolution? (If not, please enlarge; you would have me completely nonplussed!)
Frankly, I cannot treat that assertion seriously. Firstly, there is for a start a difference between generations, which by definition is evolution. OK, I grant that statistically speaking such a tiny change is typically undetectable or apparently negligible, but remember that a typical mutation begins with a single event in a single organism. Natural selection does not say non-randomly: hey, time for a selection event; lets have a new gene appear in one thousand flies (or flowers or mould cells, or sardines). A single nucleic acid change in a single cell is the start. It might take several subsequent changes to fix and optimise the effect in response to selection, but each of those in turn starts in one organism. Adaptive evolution is not a single event, a population suddenly switching from one phenotype to another; it begins by selection of one parent and develops from there.
Of course, if the original change is say, recessive or otherwise silent, growing adventitiously in the population, the frequency might (ahem!) randomly increase in the population because of founder effects and the like, but how are you going to argue that that is non-random?
>So that means based on genetic variation we can not conclude evolution is random. (Because most of these genetic variations are discarded)<
Sorry zomgwtf; that is a simple non-sequitur, even in the light of your own claims. Would you care to rephrase it?
>Evolution is partly based on the genetic variations so randomness does play a role but evolution is not dependent on random acts. That's to say, it doesn't matter what comes out of the genetic variations evolution will still happen.<
That was not a great deal better. Darwinistic adaptation depends on natural selection, ie differential reproduction in terms of heritable differences within a population. Theoretically this does not demand randomness in either genetic change or ecological circumstances. In practice however, there is little possibility to predict either the genetic changes, or the details of the empirical events.
So far so random!
***BUT*** given certain information about changes in the environment and the populations within it, we can make some kinds of predictions. Some would be of a general handwaving type, such as “No miracles please; this is science”. I would undertake to breed pigs with wings by simple selection (no GMOs for instance), given a few million years, but to produce flying pigs by natural selection in a human lifetime would not work, even though most of their genome is simply convertible to bat sequences. Conversely, we know very well that a typical generalist ground squirrel population living in a region between forest and savannah is almost bound to produce the likes of both tree squirrels and groundhogs or prairie dogs unless there are already competitors blocking some of those options.
That is where the predictability, the non-randomness of natural selection comes in. I think it was G.G. Simpson who coined the term “evolutionary opportunism”. When we know the selective pressures and the genetic resources, we can make a very good guess at the trends of adaptation.
>No where in theories of evolution will you find that evolution specifically chooses larger, faster, stronger, brighter etc. animals over another.<
Do I smell straw? I am not aware that I suggested that you would find anything of the type. However, I do propose that natural selection would indeed favour such creatures very specifically indeed, as long as a) there was nothing stopping it; and b) these attributes were favourable to their successful reproduction. In fact, you do not make it clear why you urge this, because it is exactly a point that illustrates the fundamental nature of non-randomness in evolution!
>It all comes down to inheritance of genes, the animals that pass on their genes carry on the evolution of their species. Period. <
Yes? I find it hard to take that with a straight face. Would you care to explain either what anyone said to deny it, or what it has to do with either the randomness or non-randomness of evolution?
>Nothing is random about this at all and over time it's clear that the animals that pass on their genes are the best adapted for the enviroment and have a higher probability of being chosen to mate with. <
Zomgwtf, that sounds sooo cogent! Nothing is random about it hm? I have never seen a finer example of proof by re-assertion. I have at tedious length (let’s see you deny that!) demonstrated aspects of randomness and non-randomness in all those aspects. It is simply the way the world works. Nothing random? Next time you see an oyster or salmon or cnidarian spawning, please predict which of the offspring will be “best adapted for the enviroment and have a higher probability of being chosen to mate with”. It is no good claiming *after* the event that you could tell which was which; if that was good enough, you would win every bet on the horses or the lotteries. Remember what Bohr said about prediction?
Sorry mate! That is what randomness does. If it weren’t random you *could* predict it. You might argue that it isn’t randomness that causes a fair coin to fall unpredictably, but then what would *you* call it? Bad luck?
|Apr3-10, 01:37 PM||#42|
Or consider plants. Evolution works for all life and making sure the theory works across the board means thinking of them as well. I remain quietly confident that chance is absolutely critical for success in mating.
In fact, I would think for the great majority of organisms, it's not even close. When you have thousands of spoors or seeds going out, some with one mutation and some with another, what's the biggest factor? I propose it is chance.
One problem is that people mix up chance with the idea of 50/50. (Casinos love those people.) They aren't the same thing at all.
The effects of selection are to bias the odds, usually just a little bit. And that is enough to mean that, over long time spans, fitness of the population is usually maintained. Because when you have long time spans with thousands of generations, a little bit of selection can have a dramatic effect.
You seem to be speaking of natural selection as something deterministic. It isn't. In population genetics, a gene (or more correctly, an allele) is said to increase reproductive fitness if organisms with that mutation are more likely to have surviving offspring. But it is certainly not a guarantee.
There is a finite non-negligible probability for any allele to be either fixed, or eliminated in a population. Either result is evolution, by definition, because it is a change in the distributions of alleles within the population. I know it is not about individuals. That's why my earlier post consistently refers to populations throughout, and refers you to texts on populations genetics, which go into the maths involved.
If you have a stable population of N individuals (a nice simple ideal case to start explaining this things), then a neutral mutation has a 1/N chance of being fixed, and a (N-1)/N chance of being eliminated. There's no selection involved here at all, but it is still evolution, of course; by the definition we have both been using. (1/2N if we get into the whole haploid diploid thing.)
But what if there is selection involved. In that case a beneficial allele is one with a greater than 1/N chance of being passed on, and a detrimental allele is one with a less than 1/N chance of being passed on. In either case, the odds are stacked against being passed on... even for beneficial alleles.
The best you can say is that in the long run, the casino wins. But it does so with a random walk, and precisely where you end up depends on chance, to a considerable degree. So sure, I continue to think of evolution as "random", meaning not that all results are equally likely, but only that the outcome depends on chance.
You seem to suggest that it was inevitable that we'd end up with large brains. Why would you think that? Personally, I think luck or chance had a heck of a lot to do with it. The vast majority of other living organisms on this planet didn't go that road, so why us? You know what I think? Chance. And why not? Was it inevitable that the robust Australopithenes are now extinct, but the gracile Australopithecenes live on, indirectly, as their descendents in the Homo genus? I don't think so; but then I don't think natural selection is a deterministic forces that ensures a particular result with regard for chance.
I think if we were able to somehow wind back the clock ten million years and run it again, there's no assurance at all that large brained hominids would reach plague proportions in the present. They might, they might not. They did in the only time we've run the experiment, but to say this wasn't luck is kind of assuming the conclusion, isn't it?
Natural selection itself is not chance, I agree. But evolution is not natural selection. It is change in distributions of heritable characteristics of populations. Natural selection has an impact on evolution because it modifies the chances of life and love for individuals with different characteristics.
Cheers -- sylas
PS. Missed two posts while I was writing. I think I'll read for a bit before writing again. Pleased to meet you, Jon.
|Apr3-10, 02:04 PM||#43|
The evolution of larger brains WAS inevitable, given the conditions for survival, when they began to develop. Just because it was by chance that the brain somehow did change does not mean that it being inherited and passed on generation to generation is random as well.
|Apr3-10, 02:17 PM||#44|
Cheers -- sylas
|Apr3-10, 02:21 PM||#45|
>Random- governed by or depending on chance;<
Taken out of context this is meaningless; tautological at best. In probability theory you need to do a LOT more than that. Also in simple good sense; this is simply the kind of informal factoid that lexicographers come up with when they have asked an expert for a definitive answer and have failed to understand that they have missed half the point.
>Chance- luck: an unknown and unpredictable phenomenon that causes an event to result one way rather than another<
<snggr!!!> zomgwtf, REALLY! Would you care to paraphrase that??? So chance - luck is a phenomenon that causes things huh? Like gravity?
Yeah... riiiiiightt!!! ROFL^n!
>Evolution- (biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms<
Try writing that in answer to an exam in evolution 101 and you would get a flat zero! Don't you know a tautology when you see it? Even apart from the tautological aspects, that is nonsense as it stands. This student must try harder!
>change in the inherited traits of a population of organisms through successive generations<
This is a lot better, though not formally cogent. It hints at the right idea though. Not that it clarifies the concept of natural selection in relation to evolution, which is not at all the same thing, though the relationship between the two is commonly misunderstood. For people who don't know the context that could be badly misleading.
>Both meaning the same thing.<
zomgwtf <Haaawwwww-haaaah-haaa! da capo> That has to be the funniest thing you have said in this exchange! Have mercy, man!
>Of course randomness has effects on Evolution but that is far from being the same as saying Evolution is random. Period.<
Aaaaah! The soothing voice of sanity and authority. At last! All settled. Mmmm... yes. Sort of...
zomgwtf, ol' pal ol' chum, one little detail. Just who said that "Evolution is random"? Not me for sure. Not anyone else that I took seriously.
And: "Of course randomness has effects on Evolution"?
What is that supposed to mean? If I wrote that in an exam, I had better hope it was not an exam in evolution, or even in advanced general biology. I would be lucky to fail without a black eye from the lecturer for cheek!
Oh. Well at least that sounds authoritative!
And Sylas, many thanks for the welcome. Pleased to meet you too :-)
All the best,
|Apr3-10, 03:04 PM||#46|
zomgwtf, some of this discussion will turn somewhat on the meanings of words. Other more definite statements (like a confident claim about a particular evolutionary outcome in a given environment) are a bit more than this.
However, I have a good friend, John Wilkins, who is a genuine academic Philosopher of Biology. (That's like philosophy of science, but a specific to biological science.) And we have a mutual net-friend (whom I have cited previously) in Professor Larry Moran, who is an evolutionary biologist paying never no mind to uppity philosophers.
When the two of them start writing papers at each other, the rest of us may not get a definite answer to the original question, but we can sure learn a heck of a lot about evolution!
Larry can be summarized as "evolution by accident" is an accurate description of how evolution occurs, pointing to how chance and contingency are deeply involved in every step of the way from the sources of new variations to the events which lead them to be passed on, or not; much as I have done. John, on the other hand, can be summarized as "evolution is not fundamentally a random process." He doesn't deny the obvious role of chance in mating, in survival, in mutations, living long enough to breed and so on. But he tends to draw a sharper boundary between the chances and the processes of evolution. Both are quite prolific contributors to the old talkorigins archive, and they continue to comment on each other's blogs on this and other matters.
I'll see if I can get some references, which shouldn't be taken as closing the debate, but seeing how various other people have approached this question.
Cheers -- sylas
|Apr3-10, 05:03 PM||#47|
I'm sorry if im unable to make myself clear. Once again, i can suggest you read the following text:
"Inside the Human Genome" by John C. Avise
..tho i feel that even after you've read his extremely clear, erudite discussion, you'll come back with the same questions.
tkjk, md <ret>
|Apr4-10, 03:47 AM||#48|
I cannot agree where you say "One can not have 'constrained randomness'. " I would go further and ask where we can have unconstrained randomness. I have never seen an example.
Just to forfend any misunderstandings, I think that Darwinism is a class of process, the course of which is affected by innumerable "random" effects and events, but which none the less is far from random in its nature and effects, so let us not get side tracked. What I am speaking about now is about randomness, not natural selection.
As I have said elsewhere, selection (not necessarily in the Darwinian sense!) from an unconstrained set is hard to imagine. In fact, equiprobable selection from an infinite set, constrained or not, is a very slippery concept, fraught with paradox. No one in human history has managed to make a random selection from even the numbers in the interval 0-1.
No one ever will.
How do I know? Because there is not enough matter in the observable universe to represent any number from any *subset* with a non-zero probability of fair selection.
Randomness from our point of view has to do with lack of information. The information might not be there at all, if various physical theories have any substance (personally I conditionally accept those theories, simply because I am not equipped to deny them and they seem to work in practice, so my inability to see how things can "just happen" is irrelevant. Mind you, it does seem to me to have a lot to do with the Aspect experiments and the Bell inequality.)
However, one need not appeal to quantum theory. We live in a chaotic universe. Consider a thought experiment : you have two (perfect) pool balls on a (perfect) pool table. One ball is at an arbitrary point on the surface, such that it is not perpendicular to any wall where there is a pocket. Put the cue ball on the surface perpendicularly between that ball and the table wall.
Got it so far?
Now Mr Super-player gives the cue ball a hefty whack so that it hits the first ball against the wall, and bounces against the cue ball. The two balls merrily go bouncing back and forth, and being perfect balls on a perfect table, they go on bouncing on the same line forever, right?
We had better assume that Mr Super-player is very symmetrical of course, because think what would happen if the balls were to strike each other off-centre by even the minimal Planck's distance, what... 10^-40 m? how many impacts would it take before we got a complete miss? If you bother to calculate it, you will be shocked at how quickly it would happen. In real life, you would be doing very well to get even *two* collisions (try it if you don't believe me!) Even the gravitational effect of Schroedinger's cat sneezing in its box 10000km away round the planet would disturb our ideal balls more than enough to prevent a long series of impacts.
Now, randomness in evolution has little to do with equiprobability, but it has much to do with unpredictability, and precise predictability is alien to our universe. To understand the role of randomness in evolution one has to understand those facts even more than one has to understand the nature(s) of randomness.
Just a few thoughts...
PS Oh, and btw, if anyone still thinks that evolution is random in any naive sense, let me refer him once more to the list of books I mentioned earlier in this thread. They are by far not the only ones, and any aficionado will have his own list, but they should suffice, no matter how one defines randomness in any defensible way.
PPS. Let's stop again for a think, thank, thunk. Let's reject all hidden variables in physics, sticking to the purest QM view of reality. OK? Now, that means that the basis of any event or effect in nature is fundamentally random, right? OK again?
That implies that all events in nature, whether the snozing of a sneeze, the falling of a stone, the running of a race, the raising of a skyscraper, the digestion of a steak, or the absorption of a microgram of Po, is random, right?
Rrrr... errr... well...
Maybe not quite so right. In another thread they are discussing the addition of random numbers and proof that the results must also be random. You might wish to check on that discussion. Here I merely remark that there is food for thought.
|Apr4-10, 04:02 AM||#49|
>It is just possible that we've online before. ... P*t*r Ny*k*s is a mutual, uh, acquaintance. <
Oh, right! I had almost forgotten that!
Such contacts, whether on USENET or any constructive forum are in my opinion enormously educational if one takes them in a suitable spirit. The gentleman in question seems to have taken our debate less affably, and did not respond to my greeting the next time we encountered each other.
Pity, still... plenty of other congenial spirits on line! For example, in a months correspondence I cannot remember his making a single substantial statement, whereas in this present forum I disagree with much that some people say, but at least they are saying things and mostly staying friendly!
My respects and thanks accordingly, to all of you!
All the best,
|Apr4-10, 08:17 AM||#50|
Jon and Sylas, can i have your thoughts on my posts? especially this post no.27
|Apr4-10, 10:19 AM||#51|
I had been thinking of doing this anyway, sganesh88, so here goes.
A more plausible example would be mutations which made the prey species a little bit closer in color to the sandy sea floor on which they live, or a little bit more different. When a predator moves in to grab a meal they are a bit more likely to end up eating a prey individual that is seen more easily. Over time, the mutations that become fixed in the population are more likely to be those that help make the prey closer in color to the sea floor.
Under these conditions, the tendency to the coloration might seem inevitable. That's not necessarily the case, however. There are other strategies that might have been hit upon; such as developing a propensity to feed amongst the darker seaweed, or burrow in the sand.
About the only certainty is that there will be evolution.
Ghandi had four children, and a fair number of grandchildren; but not exceptionally so. He was in many ways a lousy parent.
Einstein had three children, one of whom gave him grandchildren.
Lincoln has no surviving descendants at all; the last died in 1985.
It seems to me that you have mixed up a personal and humanist view of greatness with a biologial and evolutionary view of fitness.
There's another thing I have been meaning to add into this thread. It's a common presumption that evolution leads to "better" and "better" organisms, in some sense. This can be misleading.
Living creatures are already well suited to their normal environment. The major competition they have is with others in their own species.
Frequently, the changing characteristics within a population is a crucial part of the environment for determining fitness. An animal which lives quite nicely thank you at one time might not fare so well if suddenly transported to live with its own descendants a hundred thousand years hence, even if the environment is otherwise identical. It would likely be outcompeted. But, ironically, the individual a hundred thousand years hence suddenly restored to its ancestors might also fare less well, in that it has been moved out of the milieu for which it was adapted.
A very common feature of evolutionary change is related to sexual selection; natural selection in the way of winning a mate. To this end, many creature evolve bizarre structures and forms. Impossibly overweight antlers. Flashy plumage or enormous gaudy tails. A bright red rump. And so on. And perhaps also a large brain fits in here as well. The idea is seriously proposed and there's no reason to reject it on evolutionary grounds. It's a hypothesis to be tested, and it can be tested indirectly; correlating sperm competition with brain size in primates.
Precisely what features end up being selected in this way can depend on accidents of mating preference and this MIGHT actually be something "chosen" for a creature with the capacity to think and reflect on the matter, if we acknowledge such a thing as free will. That's partly why I think the free will thing is a distraction that misses the real points at issue here.
Cheers -- sylas
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