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Old 2006-09-08, 21:42   #1
ewmayer
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Default Evolution: The Scientific Evidence

I'm starting this thread as a spinoff from the Does God Exist? discussion, because I think the scientific evidence for (and against, if someone can provide such) the Darwinian theory of evolution by way of natural selection and its later refinements (by such luminaries as the Huxleys, Mayr, Eldredge, Dawkins, Wilson, Gould and many, many others) deserves its own thread. If you think any posts in the progenitor thread also say enough about the scientific basis of evolutionary theory to warrant their being moved or copied here, please let me know.

First, a disclaimer: I am not by profession an evolutionary biologist. I do have a thorough training in the methods of science by way of education, inclination and vocation, and try to maintain a broad interest and level of informedness in general science by way of avocation. If any trained evolutionary biologists find any glaring errors of omission or commission in my comments, by all means, please do point them out.

Useful Links:

- Janet Browne's magisterial 2-volume biography of Darwin: Volume 1, "Voyaging"; Volume 2, "The Power of Place". Wonderful in its desciption of Darwin and the closely interlinked milieu of the Victorian scientific, technical and industrial explosion which made his researches possible.

- Classics of Evolutionary Science: Richard Dawkins, The Selfish Gene

- If you want some nice specific examples of evolution in action, check out this website.

- Popular long-running evolution-focused weblog in the New York Times, by evolutionary biologist and author Olivia Judson.

- (07 Mar 2007) Darwin's God: Interesting article on the emerging science of the evolutionary aspects of religious belief among humans in the latest issue of New York Times Magazine. (Permalink)

- (20 Mar 2007) Scientist Finds the Beginnings of Morality in Primate Behavior -- New York Times (Permalink)


Related Threads:

"Astonishing Parasite" -- on the interesting mechanism used by the Toxoplasma Gondii parasite to increase the chance that it gets back from its rodent host to its cat host in order to be able to replicate.

Darwin Rules, but Biologists Dream Paradigm Shift

From a Few Genes, Life’s Myriad Shapes

---------

I'll add more links to this post as I get time to collect them, and as they are recommended to me.

Last fiddled with by ewmayer on 2007-07-10 at 20:07 Reason: Added "Related Threads" header
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Old 2006-09-08, 21:51   #2
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Originally Posted by Uncwilly View Post
As best that I can tell, "evolution" as a theory, attempts to explain things post facto.
You've apparently been reading to many ID tracts. Allow me to ask: have you actually *read* Darwin's famous work? (Fear not - it won't bite.) Now of course Origin of Species is far from the last word on the subject (that's one of the key differences between science and religion - in the former "truth" is not established by fiat and then frozen forever), but most of the fundamental aspects are there.

In any event, you appear to be misapprehending the "observe the world around you, and based on your careful observations and study, make testable hypotheses as to fundamental mechanisms and processes" phase of science with an equally-important aspect, namely that any scientific theory must not only explain the known facts, but must also make nontrivial predictions that were not obvious from mere observations. For instance, general relativity not only explains precisely by how much the bending of starlight by the sun should differ from the Newtonian theory and the gradual "anomalous" precession in the perihelion of Mercury, it also predicts the changes with time in the orbits of close binary compact objects due to gravitational radiation, the formation of black holes, and gravitational waves - none of which had ever been observed or (in the first and third instance) even conceived of before.

The theory of evolution similarly explains most of the known facts (and in cases where there seem to be glaring problems, scientists go to work and if the theory is found wanting, it is suitably revised or extended - specific subtheses might even be falsified, but the theory as a whole and its most basic tenets have withstood the test of time extremely well.) You have to remember that "evolution" is not a monolithic dogma, it's a scientific theory - or better, body of theory, since biological systems are immensely varied, dynamic and complex. (Unlike relativity, it also cannot be precisely expressed by way of a handful of exact mathematical equations - that doesn't make it "arbitrary" or "unverifiable" by any means). There are many aspects to it, many areas of (often heated) debate and quite a few things Darwin didn't have an answer for (detailed mechanisms by which speciation occurs, or whether evolution tends to be gradual and continuous, or fast and episodic), or of course simply couldn't know about at the time (for instance the detailed mechanisms of heredity, the various of ways of encoding genetic information, DNA vs. RNA, the types of replication errors that can occur, the possibility of lateral gene transfer among e.g. bacteria, the fact that new species can arise in other ways, e.g. one cell swallows another and instead of digesting it, winds up harnessing it for its own use - that's where various of our cellular organelles like mitochondria appear to have come from). But that's the beauty of science - it's a truth-seeking process, not a rigid creed not open to question. and the general consensus among scientists who actually work in the field and scrutinize aspects of evolutionary theory for a living is that Darwin got the basic idea spot on: that, given enough time and a suitable biological substrate, by way of random mutation and recombination and continuous selection for fitness, species evolve or go extinct, and entirely new species may arise.

So let's get down to the nuts and bolts of something which Darwin couldn't have known about but which the theory he founded successfully predicts. Using the above example of cellular engulfment giving rise to cellular organelles such as mitochondria, ask yourself: when a formerly free-living organism (the thing that got engulfed by the hungry cell and whose descendants evolved into the mitochondrion) becomes symbiotic with another (in the sense that the other assumes the work of providing some if its basic biological needs), what happens to the portions of its genome which supported the functions it no longer needs to take of? Well, since certain formerly-key genes are suddenly no longer needed, whether they function properly or even exist at all is no longer crucial to the organism's survival. So we might expect formerly highly-conserved genetic sequences (e.g. ones related to respiration or propulsion) to possibly drift and mutate into disuse or eventually to disappear entirely, to "wither on the vine" as it were. Guess what? that's in fact precisely what is seen in nature - symbiotic or parasitic organisms that have a major portion of their life needs provided by another species tend to have greatly reduced genomes. This is one example where the direction of evolution is not toward greater complexity (as the ID folks seem to think evolution inevitably requires), but toward greater simplicity. What evolution *does* in fact require is change in the general direction of "greater fitness", and precisely what that entails depends entirely on what environmental changes a species (or evolutionary sequence thereof) is subjected to during its history.

Another example: the clearly identifiable hand, finger and wristbones of whales - why go to the trouble of "creating" complex structures like that for an aquatic creature, when a much simpler fish-like fin will do? Again, science has a satisfying answer (whales evolved from animals that used to live on land or on continental margins - once their evolutionary ancestors became fully aquatic, they no longer needed those limbs to support their body weight but rather for propulsion and steering, so at the same time their bodies could get much larger, their "hands" gradually evolved to become less hand-like and more fin-like) and lots of clearly intermediate species represented in the fossil record, whereas ID/creationism has what, exactly? Jonah? Fossils magically being made to appear much older than they really are? God playing pranks on the silly paleontologists?

Of course many of the details are still being worked out - for example with respect to new species arising, there's been a long-term debate about precisely what the mechanisms for that are. It's known that genetic mutations occur, i.e. that by way of mis-copying errors genomes change over time, and that once a pair of genomes that both evolved from a common ancestor differ enough, their owners may no longer be able to get together and produce viable offspring - a so-called speciation barrier arises. But especially among species that reproduce sexually, what allows genomes to diverge so far in the first place? One proposed mechanism is geographic isolation, which gives rise to so-called allopatric speciation - start with a single species (which has lots of variation in the individual's genomes, but none so great that the individuals can't mate and produce viable progeny), remove half the population to a remote island and allow the two separated populations to evolve independently.

(continued below)

Last fiddled with by ewmayer on 2006-09-08 at 22:35
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Old 2006-09-08, 21:52   #3
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Originally Posted by ewmayer View Post
I think the scientific evidence for (and against, if someone can provide such) the Darwinian theory of evolution by way of natural selection and its later refinements (by such luminaries as the Huxleys, Mayr, Eldredge, Dawkins, Wilson, Gould and many, many others) deserves its own thread.
Disclaimer: I'm not a trained evolutionary biologist, despite being employed by the Genetics Dept of Cambridge University.

I am, however, a sucker for playing Devil's advocate.


Although there is excellent evidence for most of Darwin's basic theory of evolution, there is also excellent evidence for a small part of Lamarck's alternative. This, as everyone knows, has that acquired characteristics can be passed on to offspring.

The phenomemon was first (as far as I am aware) convincingly demonstrated in Zea mays. A few months ago a paper was published in Nature reporting the same effect in Mus musculus.

The word "paramutation" is a good starting point for your searches to find out more.


Neither of these cases deny that evolution takes place, quite the reverse since they both demonstrate inheritable changes in the structure of an organism. They illustrate that the standard theory is not the whole story.


Paul

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Old 2006-09-08, 21:57   #4
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(continued)

This illustrates one example of a prediction made by evolutionary theory, namely that over time, species will adapt to increase their fitness for the environment in which they live. In our example, perhaps the island has a limited food supply - say the species in question is some kind of seed-eating bird, and the kinds of seeds they find on the island are smaller and harder to find than they were in their former range. The theory predicts that over time the birds - assuming they don't go extinct as a result of their move - will evolve to be better suited for life in their new home: large individuals or ones who like to fly a lot might be at a disadvantage, because they can't find enough seeds to fuel their behavior. Not enough food means less energy to mate and raise and defend yourself and your offspring, and over time, those kinds of individuals become less and less in the population, as do any genetic particularities that may have been associated with their special physical and behavioral traits. Or perhaps the island has a new kind of predator the birds never saw in their former home - say a species of large brown tree snake, which likes to slither up the trunks of trees and devour clutches of eggs it finds in birds' nests there. If our bird species has enough variation so that some birds have a tendency to build their nests further out, among the thinner branches where the snake can't get at them, those eggs will be much more likely to hatch instead of to get eaten. Now those particular birds might do so as a result of some behavior-influencing genetic trait, or simply because they have the small-body-size gene, which allows them to build a smaller and lighter nest than their larger brethren, and thus to stay out of reach of the snake. None of those details really matter in the large view - all that matters is that individuals that are somehow more able to survive and thrive in a particular niche will be better able to reproduce and thus will pass along any genetic traits associated with their better fitness to their progeny. Reproduction and natural selection as a fitness amplifier - A wonderfully simple, yet profound idea, with immense explanatory power.

But geographic isolation is only one possible mechanism for speciation - there are many examples in nature (the birds have been especially studied in this regard, perhaps because they lend themselves to observation) in which there seems to be speciation occurring even though the 2 subspecies in question still share the same range, i.e. where geographic isolation is not a viable mechanism. (This is an example of something Darwin missed, BTW - but Einstein didn't know about gravitational radiation or black holes when he formulated general relativity, either: does that invalidate the entire theory?). What's going on there? Well, this is one of those examples where nature (which is always the ultimate arbiter in all matters scientific) throws you a curve, and as a result some part of the applicable theory needs to get modified - in some cases whole new scientific subfields arise as a result. Continuing with our example, by what mechanism might non-geographic or sympatric speciation arise? In many instances, it seems to come down to something completely arbitrary which nonetheless produces a clear result: female mate choice. Say you have a species in which all the males have the same bright blue tail feathers, which the females have long used to select mates. Now the tail feathers don't help their owners survive or obtain food, but healthier, more well-fed males tend to grow longer ones. Theory predicts that over the course of time the species will evolve so that females will tend to prefer males with longer tail feathers, not because the tail feathers are any good to the females, but because males who have plush ones *are* good as far as mates go. will this process go on indefinitely? No, because at some point ever-longer tail feathers may actually begin to impact their owners' survival odds in a negative way - they might make them easy to spot by predators, or slow them down and make them easier to catch. But in some cases such things can get pretty extreme - consider the male peacock, for instance. It all depends on the eternal tradeoff between the energetic and survival cost of showing off for the ladies, and the reproductive benefit obtained thereby. Note that at no point does the female's mate choice ever require conscious preference - evolution only cares that females tend to pick the fittest males as mates, not how they determine fitness. So far, so good. Now say at some point a mutant male is born, whose tail feathers are not larger than those of the normal blue-tailed males, but happen to be bright green instead. Now say for some reason the females of the species turn out to really go for a guy with green tail feathers, perhaps entirely by accident - perhaps they have some bright-green beetle as a major food source, meaning that over time their visual receptors evolved to be more sensitive to a certain subportion of the visual spectrum containing the greenish tints of the beetle, but also happening to overlap with the color of new male's tail plumage. In other words, the females have evolved to associate a certain range of metallic green colors with good things, so they really go for the new guy. If he's in fact less-fit than the blue-tailed males this may actually be counterproductive in terms of species survival, but as long as there's sufficient genetic diversity (some females will still be willing to mate with blue-tailed guys), the species will likely survive the temporary hiccup. On the other hand if Mr. greentail is similarly fit as his blue-tailed buddies, a strong female mate choice in his favor may cause the greentail mutant to quickly spread throughout the population.

This is an example of natural selection by way of more-or-less arbitrary mate choice bias rather than actual fitness and was something Darwin didn't anticipate. But once it was clear that it did occur in nature, did it "overturn" evolutionary theory in some large-scale way? Of course not - it was an additional refinement, a twist in a long and fascinating tale (or "tail," in this particular instance). More importantly, once it was factored in, when combined with "classical" evolutionary theory it explained a lot of previously puzzling phenomena. That is the hallmark of a successful scientific theory. There are many such apparent paradoxes which evolution has successfully explained (often after much study, debate and refinement - science can be a messy process, but don't confuse the quality of the process with that of the results), for instance the evolution of both aggression and cooperation (often side-by-side within the same species), of both greed and apparent altruism, love and murder, child-rearing and infanticide.
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Old 2006-09-08, 22:04   #5
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(continued)

Another key prediction of evolution is that large-scale changes in species (e.g. the body plan of a whale as evolved from an earlier land mammal, as it is generally believed to have occurred) should occur not in a biological instant, but via a succession of identifiably intermediate forms. These need not be continuous, since in any population a spontaneous mutation may arise in one gene which has large-scale effects on some part of the body plan or organismal function (e.g. some gene influencing brain size or neuronal wiring density, or limb length, or hairiness), but in general evolution is conservative: you may have 100 point mutations in the genome, of which 99 are neutral and one affects the individual's function in a discernible way (which if it improves reproductive fitness is more likely to make it into the next generation), but if you had massive, multiple changes from one generation to the next, that genome is less likely to survive, because if you have 20 fitness-affecting mutations, 19 of which are beneficial but only one of which makes you easy prey, all the good mutations will get eaten along with the bad one. (I'm deliberately glossing over lots of details about why genomes evolve in certain ways and why it tends to bad for them to evolve too quickly, but you get the general idea).

Of course the fossil record has gaps (often quite large ones) in places - you think it's easy for a set of bones to not get gnawed by hungry predators, get buried in a way which preserves them for untold millions of years, and then get washed to the surface by spring rains in some spot where they are easily accessible, or just as some paleontologist happens to be around? You have to remember that natural processes have destroyed the vast majority of the fossil record - and in many cases (especially those of geographically localized or physically fragile species) not just of the individuals, but of the entire species - how can you find something that's literally no longer there? Luckily in many such cases just enough evidence survives in fragmentary form to give a clue as to the whole, but in some instance we have no choice but to infer the existence of an intermediate form based on the forms bracketing it in time. The earth isn't run like some giant museum, you know. But that points up another typical strategy of the IDers, namely that of replacing "absence of evidence" with "evidence of absence". Just because we haven't found full skeletal remains of all intermediate species from apelike ancestor to modern human, does that mean we should assume such species never existed? Of course not. What we have is enough partial and fragmentary evidence to help us to make plausible inferences as to the whole.

Finally, one more comment about the pace of evolution. What a lot of the anti-evolutionists use as an "argument" against the theory is something along the lines of "I want you to show me some monkey evolving into a man, right here, right now." Especially for complex species, that's just not the way it works - evolution can occur quite quickly on geologic time scales (note that gradual-versus-rapid was a huge debate within the field until not all that long ago), but on human time scales, you're not likely to see much going on in species like that. But if you want to see something evolutionary happening on a human timescale, you need go no further than your local hospital. Every time a new strain of drug-resistant microbe is found, that's evolution by natural (or perhaps man-made in this case) selection occurring. Of course it's quite a leap from multidrug-resistant TB germs to large land mammals arising from unicellular organisms - but the time scales involved in the latter are so immensely vast that none of us can really conceive of them - we can write the numbers down on the page, but when speaking of billions of years, untold trillions of creatures sharing the planet, eating each other, mating, dividing and multiplying, hundreds of millions of organismal generations, continual planetary change, both gradual and catastrophic - our intuition simply fails us. There is no such thing as "common sense" when it comes to me and you contemplating a billion years of planetary history. Ancient peoples wrote fanciful creation myths in an effort to try and understand it all - today we have better ways of understanding the grandest story of all. In that sense, I find science and religion (i.e. dogma) to be wholly incompatible. I don't care how many silly meet-and-greets between scientists and theologians the Vatican organizes (now that they've decided that provides for better PR than burning the former at the stake) - in my opinion (and Darwin and I perhaps disagree on this point) science and dogma are simply irreconcilable. I've got not problem with treating the Judeochristian bible (mainly Genesis) as another colorful creation myth, one of many, and Moses, Abraham, Jesus, Mohammed etc. as interesting people who had some very profound and useful ideas, but as someone once said put it so well: if Jesus' teachings are worthwhile, what does it matter if he was the son of god or not?

Uncwilly, I hope that provided some examples of testable, disprovable hypothesis for you to think about.

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Maybe, some with a hard science bent can help me understand why they believe in evolution as a theory. Maybe you can do the math for this: the DNA sequence of the self replicating organism (not a virus, which needs outside help) with the simplest DNA. Given a single permutation per second, how long would it take to get the right sequence?
That's the wrong kind of question. To evolution it's not about getting "the right" sequence, it's only about whether one sequence is better than another as far as increasing the survival and reproductive success of its owner is concerned. Also, there are many ways by which genomes change - you talk only of point mutations, but there are also whole-gene duplications, large sections of genes getting swapped, flipped around, even wholesale acquired from another organism. I see many useful analogies between computer code and genomes: in a large complex piece of research code you typically will find active functions (coding elements), inactive ones and comments (silenced genes or so-called "junk" DNA), rapidly changing sections (evolutionary "hotspots"), errors that affect function in a greater way (critical bugs) or a lesser one, and so forth. Of course the analogy is far from perfect, but it gives rise to one useful way of thinking about evolution.

Now you or I individually might only be able to write a few thousand useful lines of code in a month or a year, but what if there are millions or billions of coders all working at the same time, freely exchanging sections of code, algorithmic ideas, and so forth? Compare what kinds of things you can do on a humble PC today with what was available just 20 years ago. Is that not a massive leap? Is it not possible to imagine that at some point in the not-too-distant future there might arise a computing technology which, by any reasonable standard, demonstrates self-awareness and self-guided adaptation? (Let's leave discussion of "souls" out of it - the soul is a religious concept, not a scientific one.) Now natural evolution is of course not as guided and cooperative as the human behavior that gave rise to (say) modern microprocessor technology and the software that runs on it, but on the other hand, evolution has had a considerably longer time frame to get from there to here, didn't it?
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Old 2006-09-09, 04:20   #6
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Quote:
Originally Posted by Uncwilly View Post
Maybe, some with a hard science bent can help me understand why they believe in evolution as a theory. Maybe you can do the math for this: the DNA sequence of the self replicating organism (not a virus, which needs outside help) with the simplest DNA. Given a single permutation per second, how long would it take to get the right sequence?
I've quoted this on the other thread but it fits better here:

Lies, Damned Lies, Statistics, and Probability of Abiogenesis Calculations

I think Uncwilly would perhaps be going to present an argument which is also presented (and thoroughly refuted) in that page.

Bruno
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Old 2006-09-09, 05:22   #7
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Ewmayer,

I appreciate your attempt at showing how evolution could work, but I have to point out that you have a LOT of ifs, maybe's, and possibles in the description. It comes down to speculation, not provable fact.

Using your example of the whale, the fossil record shows that whales were land dwelling mammals 50 to 60 million years ago. If it took that long for the whale to turn its arms into pseudo-fins, then how did humans "evolve" from an apelike ancestor in a mere 1 to 2 million years. The whale required 2 million generations to make its fins, move its air hole, learn to eat plankton, and streamline its body. How is it possible for a human to make a much more drastic change in a mere 50,000 generations? Would you claim that human "evolution" moves at a rate 40 times faster than whales? At that rate, we will reach the pinnacle of God-like power in a few more hundred years.

Please consider this an effort to encourage debate.

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Old 2006-09-09, 05:56   #8
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Originally Posted by ewmayer View Post
I'm starting this thread as a spinoff from the Does God Exist? discussion, because I think the scientific evidence for (and against, if someone can provide such) the Darwinian theory of evolution by way of natural selection and its later refinements (by such luminaries as the Huxleys, Mayr, Eldredge, Dawkins, Wilson, Gould and many, many others) deserves its own thread.
Thank you! Thank you! Thank you!

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First, a disclaimer: I am not by profession an evolutionary biologist. I do have a thorough training in the methods of science by way of education, inclination and vocation, and try to maintain a broad interest and level of informedness in general science by way of avocation. If any trained evolutionary biologists find any glaring errors of omission or commission in my comments, by all means, please do point them out.
Ditto, ditto, ditto.
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Old 2006-09-09, 06:48   #9
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Originally Posted by ewmayer View Post
any scientific theory must not only explain the known facts, but must also make nontrivial predictions that were not obvious from mere observations.
Right. All too often, in our responses to creationists' claims, we forget to challenge them to present testable nontrivial predictions that differ from evolution's predictions. If we all remembered to do that, the subsequent sputtering and hemming-hawing would put the lie to some of their pretenses.

We usually let the creationists/IDers off way too easy by allowing them to pretend that simply pointing out gaps in evolutionary data constitutes an alternative scientific theory of its own.

I'll note here that one beneficial effect of the ID challenge has been to point out various sloppinesses in our science education and evolution presentations. They're helping evolution improve its fitness for survival! Now let's help point out creationism/ID's unfitnesses! An environment of proper science education and healthy skepticism will not be kind to creationism/ID.

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quite a few things Darwin didn't have an answer for (detailed mechanisms by which speciation occurs, or whether evolution tends to be gradual and continuous, or fast and episodic), or of course simply couldn't know about at the time (for instance the detailed mechanisms of heredity, the various of ways of encoding genetic information, DNA vs. RNA, the types of replication errors that can occur, the possibility of lateral gene transfer among e.g. bacteria, the fact that new species can arise in other ways, e.g. one cell swallows another and instead of digesting it, winds up harnessing it for its own use - that's where various of our cellular organelles like mitochondria appear to have come from).
That's why I think it's a mistake to recommend that folks like Uncwilly read Darwin's "Origin of Species" first. There are so many gaps in what Darwin knew that this is liable to just assist the central creationist/ID strategy of pointing out gaps in evolution rather than presenting a real alternative. Instead, direct such folks to a more modern explanation. (I regret that I'm not so familiar with the literature as to be able to recommend any specific books, but perhaps one of Gould's or Dawkins's works would fit the bill?) Then, after they've seen an exposition with recent gap-fillings, direct them to Darwin so as to appreciate his achievement.

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when a formerly free-living organism (the thing that got engulfed by the hungry cell and whose descendants evolved into the mitochondrion) becomes symbiotic with another (in the sense that the other assumes the work of providing some if its basic biological needs), what happens to the portions of its genome which supported the functions it no longer needs to take of?
To which creationists/IDers may simply reply that that never happened: the Intelligent Designer simply created symbiotes as we see them, and thus there is no such process to explain.

I think one basic step is that we have to try to convince them (at least the young-Earthers among them) that there really were all those billions of years, not just 6,000 or 10,000 or even a million, of time in which the evolutionary processes could proceed (e.g., that radiometric dating is sound). Otherwise, they can always dismiss anything that would have required substantial time.

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Well, since certain formerly-key genes are suddenly no longer needed, whether they function properly or even exist at all is no longer crucial to the organism's survival. So we might expect formerly highly-conserved genetic sequences (e.g. ones related to respiration or propulsion) to possibly drift and mutate into disuse or eventually to disappear entirely, to "wither on the vine" as it were. Guess what? that's in fact precisely what is seen in nature - symbiotic or parasitic organisms that have a major portion of their life needs provided by another species tend to have greatly reduced genomes.
I'd recommend particular emphasis on pointing out correlations of the relative incompleteness of examples of this process with relative time intervals since onset of it in the respective species' histories. But, see -- that requires introducing the validity of dating methods first.

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This is one example where the direction of evolution is not toward greater complexity (as the ID folks seem to think evolution inevitably requires), but toward greater simplicity.
Here's where some creationists may trot out the Second Law of Thermodynamics [like they did all the time in the early 1970's when I subscribed to an ICR (Institute for Creation Research) newsletter so I could see what they were claiming, without having to buy their books to do so]. I think IDers may be less likely to, but I could be wrong.

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Old 2006-09-09, 07:27   #10
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namely that of replacing
confusing or conflating, rather
Quote:
"absence of evidence" with "evidence of absence".
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if you want to see something evolutionary happening on a human timescale, you need go no further than your local hospital. Every time a new strain of drug-resistant microbe is found, that's evolution by natural (or perhaps man-made in this case) selection occurring.
IDers respond, "Hey, we've always granted that microevolution occurs."

Quote:
Of course it's quite a leap from multidrug-resistant TB germs to large land mammals arising from unicellular organisms
IDers: "Exactly. That would be macroevolution if it ever actually happened. And you can't demonstrate that, can you?"

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but the time scales involved in the latter are so immensely vast that none of us can really conceive of them
Evolutionists shout: "Hey! We can, too, conceive of them! That's why we so confidently present evolution as reality! If we actually couldn't conceive of them, we'd all be young-Earth creationists."

Quote:
but when speaking of billions of years, untold trillions of creatures sharing the planet, eating each other, mating, dividing and multiplying, hundreds of millions of organismal generations, continual planetary change, both gradual and catastrophic - our intuition simply fails us. There is no such thing as "common sense" when it comes to me and you contemplating a billion years of planetary history.
Astronomers: "Speak for yourself, buddy! We are quite accustomed to this stuff (maybe not the eating, mating, dividing, and multiplying parts unless we're exobiologists). That's why one colloquial meaning of astronomical is 'enormously or inconceivably large or great in extent or degree' [Webster's Third New International Dictionary] :-)"

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I don't care how many silly meet-and-greets between scientists and theologians the Vatican organizes (now that they've decided that provides for better PR than burning the former at the stake) - in my opinion (and Darwin and I perhaps disagree on this point) science and dogma are simply irreconcilable.
I disagree with you, too. (And I've stood next to Darwin's gravestone in Westminster Abbey!)

The science of psychology does provide adequate explanation for reconciliation of science and dogma. Not rapid or easy reconciliation, mind you ...

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if Jesus' teachings are worthwhile, what does it matter if he was the son of god or not?
Answer from psychology: Some people need that authority (son of God) in order to accept the worth of the teachings.

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That's the wrong kind of question. To evolution it's not about getting "the right" sequence, it's only about whether one sequence is better than another as far as increasing the survival and reproductive success of its owner is concerned.
See brunoparga's suggestion of "Lies, Damned Lies, Statistics, and Probability of Abiogenesis Calculations" at http://www.talkorigins.org/faqs/abio...rob.html#Intro

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Compare what kinds of things you can do on a humble PC today with what was available just 20 years ago. Is that not a massive leap?
Uh, isn't this making the ID argument for them here, Ernst?

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Is it not possible to imagine that at some point in the not-too-distant future there might arise a computing technology which, by any reasonable standard, demonstrates self-awareness and self-guided adaptation? (Let's leave discussion of "souls" out of it - the soul is a religious concept, not a scientific one.) Now natural evolution is of course not as guided and cooperative as the human behavior that gave rise to (say) modern microprocessor technology and the software that runs on it,
IDer: "Oh, yes, it is."

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but on the other hand, evolution has had a considerably longer time frame to get from there to here, didn't it?
Young-Earth IDer: "Oh, no, it didn't."

Last fiddled with by cheesehead on 2006-09-09 at 08:19
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Old 2006-09-09, 14:45   #11
jinydu
 
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There are several other lines of evidence, besides radioactive dating, that indicate that the Earth is well over 10,000 years old. Astronomy has already been mentioned. Another example is plate tectonics. If one accepts that the supercontinent Pangea existed at some time in the past (and this is supported both by the close fit of the coastline of South America with that of Africa, and by fossil evidence indicating that land animals were able to travel across continents) and one accepts the measured rates of continental drift (which have been measured directly using lasers in recent decades), one can easily calculate that Pangea must have existed many millions of years ago.
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