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Author | Topic: Key points of Evolution | |||||||||||||||||||||||||||
Adminnemooseus Administrator Posts: 3976 Joined: |
Others are interfacing with you and contributing to the problem, but it seems to me that you are posting more than your fair share of off-topic blather messages at various topic. As in, I've seen at least 2 posted today. Stop it.
No replies to this message. Replies may result in a 24 hour suspension. Adminnemooseus
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Coragyps Member (Idle past 761 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
Biology: A Custom Edition for Anoka-Ramsey Community College - 2005 - (Campbell; Reece) Inquiry Into Life - 2003 - (Sylvia Madder) Campbell's other texts are fairly highly regarded, though I haven't read any of them. Mader's Biology is clearly written and, I thought, a pretty good text. And yes, newer is probably better: biology is moving awfully fast.
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RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
That was disingenuous. I'm perfectly serious. There are a number of chemical reactions that are dependent on environmental factors (heat, acidity, light, catalysts, etc etc etc) and thus are unpredictable no matter how predictable the electron behavior is (and I challenge that concept as well). Evolutionary events happen all the time -- a C replaces and A in a strand of DNA -- and they are just as repeatable as any electron behavior. Enjoy by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
If you test for the effect of an electron in an atom, you can reapeatedly test over and over again the same element and compare the results. Therefore, you can confirm your theory. Likewise you can look at changes in DNA and see if the same kinds of changes are repeated. It takes many such "events" to add up to some noticeable change.
Now let us say we are dealing with an evolutionary event that is supposed to have happened billions of years ago. The problem here is definition. What is MEANT BY an "evolutionary event" other than a mutation (repeatable changes in DNA)? Or are we talking about the accumulated effect of many many "events" rather than a single one?
Second, the environment that existed that long ago cannot be known so its effect ... We can actually know quite a bit about the environment.
Third, it seems the mechanisms for evolution would allow for evolution to occur in any direction. Of course. And even to go back and forth occasionally. There is no direction other than survival and breeding.
Life does not always evolve from a less complex form to a more complex form. Actually, I believe I have read somewhere that it would be more logical for life to evolve from the complex to the more simple. It can - and does - do both. Vestigial organs are an example of a trend to less complexity, as are blind cave fish.
If you were only dealing with natural selection then you may be able to theorize a particular path, but with the many different mechanisms which are now believed to be part of the evolutionary process this would not seem to be the case. Path to what? There is no purpose to natural selection - it is just different organisms with different ability to survive and breed.
How can we make a conclusion about an evolutionary event that occurred that long ago when the event cannot be repeated in the present. It would appear that whatever evidence appeared in nature, no matter what direction was taken, it would never disprove or falsify the present theory of evolution. Let's start with some definitions: Evolution is the change in hereditary traits in populations from generation to generation. A repeatable "event" is a change in hereditary traits from generation to generation -- you don't have to repeat the same changes, just change. Speciation is where a parent population divides into two or more daughter populations that no longer interbreed. A repeatable "event" is a speciation division of descendant populations from a common ancestor population. It doesn't have to be the same division, just division. The THEORY of Evolution is - simply speaking - the theory that these two basic mechanisms are all that are needed to explain the diversity of life as we know it, today, in history, in the fossil record, and in the genetic record. We test that theory against the evidence. We look at the "events" in the various records and see whether in fact they are due to the mechanisms of evolution. by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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lyx2no Member (Idle past 4743 days) Posts: 1277 From: A vast, undifferentiated plane. Joined: |
That brings me back to my original question. How can we make a conclusion about an evolutionary event that occurred that long ago when the event cannot be repeated in the present. It would appear that whatever evidence appeared in nature, no matter what direction was taken, it would never disprove or falsify the present theory of evolution. My great grandfather dedicated the last 85 years of his life dealing poker hands to himself out of a 52 card deck and writing them all down. In total he recorded 45 million hands. If no one was there to see it how could we know if it were true or false? Patterns. We could try for a trillion years and never repeat his exact 45 million hand pattern. But there are other patterns we can investigate. How many pairs, three of a kinds, two pairs, etc. did he get. How many hearts, spades, clubs and diamonds? how many reds or blacks? Numbers and faces? Odds and evens? But do the patterns we find in Gampa’s record fit the patterns we would expect to find given the predictions forced upon us by the Theory of Probability? There are many sets to test for randomness and the more tests his record passes the more likely his story is to be true. Given enough tests, and there are more than enough tests, it would be easier to do it then to fake it. Likewise, evolution leaves predictable patterns. Never in a trillion years will our experiments repeat the exact pattern the rocks have recorded. But do the patterns we find in the rock fit the patterns we would expect to find given the predictions forced upon us by the Theory of Evolution? The ToE has passed millions of test . this year. Every time someone finds a fossil in a strata it would be predicted to be in is a test. And conversely, when I look in Pleistocene lake beds I never find trilobites. One trilobite and the ToE has some ”splainin’ to do. Or as the country song goes, “You only have to kill my daddy once to make me mad.” The evidence supporting the ToE produced tomorrow will exceed the creo evidence against developed in the last century. Why can I say that? Because they have produced no evidence against ToE at all in the last century. And in the future if any one does produce evidence against the ToE it is not likely to be a creo, but a scientist. And He’ll get a prize and a cake with his name on it. Kindly Ta-da ≠ QED
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RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hello Wumpini,
Let me take a different approach to the issue of repeatability. You have (as have many creationists) raised this issue several times now:
Any conclusions made on evidence that is that old would seem to be questionable to me. Since you cannot repeat the event, it does not appear that there is any method to test these conclusions.
Message 245 That brings me back to my original question. How can we make a conclusion about an evolutionary event that occurred that long ago when the event cannot be repeated in the present. It would appear that whatever evidence appeared in nature, no matter what direction was taken, it would never disprove or falsify the present theory of evolution. The real issue is {{{what}}} are we repeating. Let's use the "evolutionary event" of the domestication of wolf into dog. We know what is actually possible from dogs, but we don't know the actual pre-historic event or how it actually happened. Now we have repeated this "evolutionary event" with foxes: Domesticated silver fox - Wikipediahttp://reactor-core.org/taming-foxes.html quote: From this controlled experiment Belyaev repeated the evolutionary event of the dogs evolving from wolves. In addition we now see that the domesticated foxes overlap the traits of the domesticated wolf, and this shows that a common ancestor population linking wolf and fox is not only possible but highly probable - without even looking into the fossil record or genetics to ascertain how recent this division occurred. That the fossil and genetic information confirm and validate this just increases the degree of reliability for this having occurred (maintaining scientific tentativity). Does that help? Enjoy. by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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Wumpini Member (Idle past 5790 days) Posts: 229 From: Ghana West Africa Joined: |
Hello RAZD,
I am still trying to figure out this scientific language.
RAZD writes: The real issue is {{{what}}} are we repeating. Let's use the "evolutionary event" of the domestication of wolf into dog. We know what is actually possible from dogs, but we don't know the actual pre-historic event or how it actually happened. Now we have repeated this "evolutionary event" with foxes RAZD writes: From this controlled experiment Belyaev repeated the evolutionary event of the dogs evolving from wolves. What evolutionary event? Dogs are wolves, and wolves are dogs, are they not? We crossbreed them all of the time in Arkansas.
RAZD writes: In addition we now see that the domesticated foxes overlap the traits of the domesticated wolf, and this shows that a common ancestor population linking wolf and fox is not only possible but highly probable - without even looking into the fossil record or genetics to ascertain how recent this division occurred. That the fossil and genetic information confirm and validate this just increases the degree of reliability for this having occurred (maintaining scientific tentativity). Does that help? To be quite honest. No. It appears you have now thrown another term into this mix of scientific communication (miscommunication). What is “scientific tentativity?” I looked up the word tentative (because I could not find tentativity):
quote: If I understand you correctly then you are telling me that the theories that scientists have about these “evolutionary events” that have occurred in the past based upon observable scientific evidence (from the past) are tentative. In other words, they are uncertain, or not fully worked out or agreed upon. Therefore, they are not facts! They are only hypotheses (educated guesses) with some “degree of reliability (as you say).” I think we may be starting to see eye to eye after all. I was beginning to give up hope but I now see a glimmer in the distance. As I said a number of posts back, it could be that we are using different words to communicate similar ideas. Here are some thoughts that I had about your analysis of Belyaev’s experiment. As I said, I don’t know what you mean by dogs evolving from wolves. Folks in Arkansas crossbreed dogs with wolves all of the time therefore I would not think this would be an “evolutionary event.” Answers - The Most Trusted Place for Answering Life's Questions At least, that is not what I have in mind when I think of an “evolutionary event.” An “evolutionary event” could be the explanation of where these dogs (wolves) originated. Is that a repeatable event? How do scientists say this fossil is an ancestor of that fossil when the organisms are no longer around, and the type of environment can only be assumed. There is no way that the event can be repeated! For example with your dogs (wolves), it appears that scientists would theorize that they have evolved from an early carnivore known as the Miacidae which supposedly evolved about 50 million years ago from some insectivores which lived during the time of the dinosaurs. When scientists find fossils of these organisms and place them in some sort of order then it would not appear to me that they could test their conclusions. They can never repeat the event to confirm that the order is correct. To state that the theory that "dogs (wolves) evolved from a totally different animal (Miacidae)" is an “evolutionary fact” based upon scientific evidence would seem to be incorrect. I am not sure that the theory (that dogs evolved from Miacidae) is even scientific since it does not appear that it can be falsified. However, it may be that this is a “theory with scientific tentativity.” If that is the case then I need to come to a better understanding of what is meant by that term. There is a big difference between stating that Belyaev’s experimental results are a fact based upon repeatable scientific evidence, and stating that evolution between two totally different animals millions of years ago is a fact based upon repeatable scientific evidence. It appears that to use the Belyaev experiment to attempt to confirm or deny the evolution of dogs (wolves) is not valid. The only truth that Belyaev’s experiment seems to prove is that it is possible to change the temperament of dogs (wolves) through selective breeding. It does not appear to prove anything else. It does not prove how the temperament of dogs (wolves) changed in the past. It only gives us a possibility. Another possibility would be that domesticated dogs became wild wolves. If scientists tested the theory of whether domesticated dogs through selective breeding can be made wild, they may be surprised to find the experiment works either way. In either event, it is not what I would classify as an “evolutionary event.” Here is one quote (and link) that I found about the evolutionary history of the dog (wolf) family. Answers - The Most Trusted Place for Answering Life's Questions
quote: I believe that when they say the evolutionary history of Carnivora (dogs/wolves) is clouded in controversy, and patchy, and incomplete, it might be another way of sayinging they need to maintain “scientific tentativity.” I agree with the quote that the conclusions of scientists seem "remarkable" considering this limitation. "There is one thing even more vital to science than intelligent methods; and that is, the sincere desire to find out the truth, whatever it may be." - Charles Sanders Pierce
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Perdition Member (Idle past 3265 days) Posts: 1593 From: Wisconsin Joined: |
Scientists do no deal in absolute truth. They seek to get closer to the truth, but acknowledge that someone may find something to contradict their current conclusion. Even if something doesn't outright contradict their conclusion, something may be found that modifies it a bit. Scientists, when pushed or being completely honest, will always say that based on all known evidence and all currently understood natural laws, this is our best conclusion. The only way someone can claim to be one hundred percent certain is if there is no possible way they can be shown something that would make them change their minds. Scientists will never assert that...creationists generally have to, because they are starting with a premise that MUST be true for their interpretation of their religion, so no matter what else may be found, it CAN'T contradict their premise, and thus must be a lie, a test, or there must be some other convoluted way for them to justify it in their mind.
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Percy Member Posts: 22499 From: New Hampshire Joined: Member Rating: 4.9 |
Wumpini writes: If I understand you correctly then you are telling me that the theories that scientists have about these “evolutionary events” that have occurred in the past based upon observable scientific evidence (from the past) are tentative. All scientific theories are tentative, not just evolution.
In other words, they are uncertain, or not fully worked out or agreed upon. When applied to scientific theory, the word tentative doesn't mean "uncertain" or "not fully worked out", and it doesn't imply disagreement within the scientific community. Tentative only means a theory is open to change in light of new evidence or improved insight.
Therefore, they are not facts! They are only hypotheses (educated guesses) with some “degree of reliability (as you say).” You are correct to say that theories are not facts, and hopefully no one has said otherwise. But theories are not hypotheses, either. Science begins with a hypothesis, and then proposes tests of that hypothesis. Scientists become persuaded of the accuracy of a hypothesis as a representation of the real world when it passes the tests and the inevitable challenges. A scientific consensus forms when a preponderance of scientists in the relevant field become persuaded by the evidence and the successful tests, and the hypothesis then becomes an accepted theory. The most common example of tentativity is Newton's laws of motion. A scientific law is the same thing as a scientific theory. There used to be a tendency within science to call well established principles laws. While this is not a common practice today, theories that were originally called laws are still called laws. Anyway, Newton's laws of motion are tentative, just like all scientific theories are tentative, and a good thing, too, because Einstein came along and showed that Newton's laws, while an excellent approximation for slow moving objects and not very massive objects, are inaccurate at speeds that are an appreciable proportion of the speed of light or at masses greater than the mass of Jupiter. So theories cannot be immutable facts, because that would mean they couldn't change when we discovered something new. Scientific theories have to be considered tentative so they can be updated to reflect new knowledge and understanding. The status of theory is the highest honor that science can confer upon a hypothesis, because it means that hypothesis has been rigorously tested and has passed those tests with sufficiently flying colors as to persuade most scientists. While that doesn't mean that an accepted scientific theory is the last and final word, it does mean that it would take very, very strong and persuasive evidence, at least as strong and persuasive as the original evidence, to call it into question. --Percy
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RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hey Wumpini,
I am still trying to figure out this scientific language. There are several good websites that might help, they are run by universities as part of their information for teaching evolution: Several from Berkeley:An introduction to evolution - Understanding Evolution Understanding Evolution - Your one-stop source for information on evolution Page not found Homology or convergent trait? - Understanding Evolution Some from U of Michigan:Evolution and Natural Selection The Process of Speciation http://www.globalchange.umich.edu/.../complex_life.html You could spend a fair bit of time studying those sites, so you may want to take it a bit at a time.
What evolutionary event? Dogs are wolves, and wolves are dogs, are they not? We crossbreed them all of the time in Arkansas. Well that's the issue isn't it? What do you think an "event" involves? For an evolutionary biologist it is any change in hereditary traits in a population from generation to generation -- you are an "evolutionary event" in this understanding of such terminology (although scientists probably would not use this term, because it is really many "events" at once}. The problem seems to be that he common layperson thinks there are remarkable stages in evolution that occur in a single event -- and this is a false perception.
At least, that is not what I have in mind when I think of an “evolutionary event.” An “evolutionary event” could be the explanation of where these dogs (wolves) originated. Is that a repeatable event? Yet there would be no point at which you suddenly had wolves. What you think of a single "event" is a cumulation of many events such as the wolf to dog event, which themselves are composed of many intermediate events, down to the level of generation to generation reproduction and survival events.
To be quite honest. No. Yet you asked for an example of a repeatable "evolutionary event" -- and the experiment on the foxes duplicated the types of changes found in dogs. In this way the "domestication of the wolf" event was repeated with the fox.
It appears you have now thrown another term into this mix of scientific communication (miscommunication). What is “scientific tentativity?”
... anything are regarded as tentative conclusions. This is the essential difference between scientific knowledge and knowledge based on belief - that it is tentative and subject to change when more complete understandings come along. I looked up the word tentative (because I could not find tentativity):
quote:If I understand you correctly then you are telling me that the theories that scientists have about... This is the essence of scientific theory: given these {set} of facts, plus our current understanding of "life, the universe, and everything" (Douglas Adam, "Hitchhiker" series), we can make these {tentative} conclusions ... they may or may not be true. The next thing science does is ask the question "how can we test this?" ... in other words what can be predicted by the concept and what would happen if it was NOT true. By testing we can eliminate false concepts and mistaken understandings, and thus advance knowledge by the process of elimination, but we can never prove these concept to be 100% absolutely true ... and thus (all) scientific theory is always tentative.
There is a big difference between stating that Belyaev’s experimental results are a fact based upon repeatable scientific evidence, and stating that evolution between two totally different animals millions of years ago is a fact based upon repeatable scientific evidence. But you don't ever have "evolution between two totally different animals" ... you have evolution within species, you have speciation division of populations, and you have various degrees of deviation of daughter populations from parent or sibling populations through continued evolution within each species. The dogs and foxes show you how much deviation is possible in relatively short periods of time.
The only truth that Belyaev’s experiment seems to prove is that it is possible to change the temperament of dogs (wolves) through selective breeding. Yet much more than just the temperament changed. Selection for less aggressive foxes did not select for changes in coloration, build and other features that occurred, and those changes are due to different chemical (hormone) effects during growth of the individual. The experiment did not cause changes to appear, nor did it select for different appearances.
I believe that when they say the evolutionary history of Carnivora (dogs/wolves) is clouded in controversy, and patchy, and incomplete, it might be another way of sayinging they need to maintain “scientific tentativity.” The exact path of evolution is patchy and incomplete, no argument, however there is little doubt that dogs are mammals, that they are carnivores, or that they are Canidae. I also note that your first link says:
quote: So it looks like foxes and wolves diverged at about the same time that the ancestors were becoming recognizable as similar to wolves.
I believe that when they say the evolutionary history of Carnivora (dogs/wolves) is clouded in controversy, and patchy, and incomplete, it might be another way of sayinging they need to maintain “scientific tentativity.” I agree with the quote that the conclusions of scientists seem "remarkable" considering this limitation. Is the glass half full or half empty? Is a jigsaw puzzle that is partially complete "patchy and incomplete" until the last piece is in place? Enjoy. Edited by Admin, : Shorten long link. by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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Wumpini Member (Idle past 5790 days) Posts: 229 From: Ghana West Africa Joined: |
Thanks for your reply.
I am beginning to see why there is so much confusion in the world today about evolution (and possibly science in general). I am having a difficult time even coming to a simple understanding in simple English terms about how scientists view the process of evolution. I believe that I understand what you are saying about a theory. The theory of evolution would be that framework that explains all of the evidence (facts) that have been gathered in this field. This theory can never become final because there is always the possibility that new evidence will require an adjustment. Maybe you can help me to understand what is meant by "evolution is a fact." Here is a quote from the Talk Origins website by RC Lewontin:
quote: Can you see where I can become confused? Is it a fact or a theory that the earth is 3.6 billion years old? Is it a fact or a theory that cellular life has been around for half of that time? Is it a fact or a theory that multi-cellular life is at least 800 million years old? Is it a fact or a theory that major life forms now on earth were not at all represented in the past? Is it a fact or a theory that there were no birds or mammals 250 million years ago? Is it a fact or a theory that all living forms come from previous living forms? Is it a fact or a theory that birds arose from non-birds? Is it a fact or a theory that humans arose from non-humans? He ends the quote by stating that you can no more deny these facts then you can deny that the earth is round. I know that the earth is round. I have seen pictures of the earth. Am I missing something here? Can you understand why I am confused? Are these facts based upon evidence? How can you prove by evidence that something did not exist? I have been told that you cannot prove that God does not exist, how can you prove that birds did not exist 250 million years ago? Maybe you can give me a link where I can examine one evolutionary event to see how scientists go through this process. For example, Lewontin says it is a fact that birds came from non-birds. What is the evidence? Is it fossils or something else? How was the evidence evaluated? What conclusions were reached regarding the evidence? At what time did the evidence or theory become a fact? "There is one thing even more vital to science than intelligent methods; and that is, the sincere desire to find out the truth, whatever it may be." - Charles Sanders Pierce
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Wumpini Member (Idle past 5790 days) Posts: 229 From: Ghana West Africa Joined: |
Hey RAZD,
RAZD writes: There are several good websites that might help, they are run by universities as part of their information for teaching evolution: Thanks for the links. I have also been doing a lot of reading in some biology textbooks. Maybe eventually some of it will sink into my brain.
Well that's the issue isn't it? What do you think an "event" involves? If I had to answer this question right now, I guess I would say it would involve a significant genetic mutation that became a continuing part of the population. It appears that you keep saying that the changes are all gradual. What gives you that idea? Could the changes not have been abrupt? Could there not have been long periods of no change, and then a few significant mutations that brought about major changes? It seems that I have read about some different theories that support this idea (Punctuated equilibrium or hopeful monster). I am not sure that any experiments that are done today can give us anything more than supposition about what happened in the past. I have been many places in the world, and seen many different human beings. Some of these people live in places where they may have never seen a white man. They may have never left the area where they live. The people are different colors, they are different sizes, they have different characteristics, and they have different temperaments. However, they are all people. None of them are turning into anything else. I could move into one of these villages and begin reproducing, and in a few generations there would be different colored people, but they would still be people.
Yet you asked for an example of a repeatable "evolutionary event" -- and the experiment on the foxes duplicated the types of changes found in dogs. In this way the "domestication of the wolf" event was repeated with the fox. The wolves did not become dogs. Those wolves with a gentle temperament were selectively breeded to produce gentle wolves. However, they were still wolves weren't they? The same is true of the foxes. I am trying to get all the way from abiogenesis to diversified complex life. Wild wolves to gentle wolves seems a far cry from what I need to get there. Is the theory supposed to be that dogs evolved from wolves? Could the theory not just as easily be that wolves evolved from dogs? I am not trying to be contrary or difficult. I am really curious. Maybe as I study more about the subject, and learn more about how these changes take place, and what scientists believe happened in the past, then I can understand why you say these experiments are a repetition of some past evolutionary event.
... anything are regarded as tentative conclusions. I think Percy explained this very well. You may want to see my post about "Evolution is a fact." I think I understand what a theory is supposed to be. However, I do not understand why some are saying that many different things that could never be proven are "facts."
But you don't ever have "evolution between two totally different animals" ... you have evolution within species, you have speciation division of populations, and you have various degrees of deviation of daughter populations from parent or sibling populations through continued evolution within each species. The dogs and foxes show you how much deviation is possible in relatively short periods of time. Maybe when I spend some time with the links that you gave me it will become clearer. It seems if dogs mate with dogs they will always be dogs. If wolves mate with wolves then they will always be wolves. Maybe dogs and wolves and foxes are really like different races of people all over the world. Natural selection, sexual selection, or genetic drift will not change that fact. You would seem to need lasting mutations, and these mutations need to be positive. If you had significant positive mutations that became a part of the population, then I could see the potential for lasting change. The dog and wolf experiments do not seem to show that can take place. "There is one thing even more vital to science than intelligent methods; and that is, the sincere desire to find out the truth, whatever it may be." - Charles Sanders Pierce
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Dr Adequate Member (Idle past 311 days) Posts: 16113 Joined: |
Am I missing something here? Can you understand why I am confused? Are these facts based upon evidence? How can you prove by evidence that something did not exist? I have been told that you cannot prove that God does not exist, how can you prove that birds did not exist 250 million years ago? How can you prove that there are no winged pigs if you haven't looked everywhere? Nonetheless, if you were to say: "It's a fact that there are no winged pigs", then I wouldn't cavil.
Maybe you can give me a link where I can examine one evolutionary event to see how scientists go through this process. For example, Lewontin says it is a fact that birds came from non-birds. What is the evidence? Is it fossils or something else? How was the evidence evaluated? What conclusions were reached regarding the evidence? At what time did the evidence or theory become a fact? Well, let's have a look at that shall we? Hypothesis: modern birds are the product of evolution. Prediction #1: there should be something that, in morphological terms, they could have evolved from. Potential falsification: if there wasn't anything. Actual observation: the existence of small bipedal archosaurs. Prediction #2: Since these are the only candidates, we predict that there must have been bipedal archosaurs before birds. Potential falsification: fossil birds in Devonian rocks (for example). Actual observation: the fossil record is consistent with the hypothesis. Prediction #3: In the fosil record, therefore, we should find things which are morphologically intermediate between archosaurs and modern birds, and we should not find chimerical forms between a bird and anything else. Potential falsification: complete absence of sauch desired intermediate forms; the existence of chimerae (as, for example, if the platypus really was duck-billed). Actual observation: feathered, wingless theropods, feathered gliding theropods, dino-birds such as Archaeopteryx. Prediction #4: Birds should be genetically closer to the other surviving archosaurs (e.g. crocodiles) than to anything else, and vice versa. So a crocodile should be genetically closer to, for example, a hummingbird than it is to a Komodo dragon. Potential falsification: a contrary observation, obviously. Actual observation: bang in line with this remarkable prediction. In the light of such evidence, we can either regard the hypothesis as established, or we can suspect that God is messing us about. I'll go with the former option. Edited by Dr Adequate, : No reason given.
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Percy Member Posts: 22499 From: New Hampshire Joined: Member Rating: 4.9 |
Wumpini writes: Maybe you can help me to understand what is meant by "evolution is a fact." This is a tough one. Most people would agree that a simple observation is a fact. You look at a car and observing its color say, "The car is red." Everyone would agree you've just stated a fact. Now you stick a thermometer in a glass of water and observing the thermometer reading say, "The temperature of the water is 72.4oF." Everyone would again agree that you've just stated a fact. But there's something very interesting about considering the measured temperature of the water to be a fact, and that's that though we take the measurement of temperature for granted, our ability to measure temperature actually depends upon a number of other facts. First there's the observation that most materials, including mercury, expand with increasing temperature. Second, there are the observations that water freezes and boils at certain fixed temperatures (32oF and 212oF respectively) that provided us the Fahrenheit temperature scale. And then there was the discovery that open thermometers were also sensitive to air pressure, so sealed thermometers were developed. So you can see that even your simple observation of temperature, this simple fact, is actually based upon a number of other facts. Evolution is similar in that the conclusion that evolution actually played the major role in the history of life on this planet depends upon a number of simpler facts, and literally millions of observations. The three most significant facts are:
From all these facts it is concluded as an inescapable fact that evolution happened on this planet. A lot! The theory of evolution attempts to explain the mechanisms behind the evolution that we observe in the fossil record, in the diversity and relatedness of life, and in the genetic record. So now that you understand that facts can depend upon other facts, I'll answer your fact/theory questions.
Is it a fact or a theory that the earth is 3.6 billion years old? The earth is thought to be 4.56 billion years old. That the earth is billions of years old is a fact. That it's precisely 4.56 billion years old is less certain, and I wouldn't call it a fact. It would be like saying about your car that it's a fact that the gasoline tank holds less than 20 gallons, but whether it's an actual fact that the tank holds precisely 16.3 gallons as the owner's manual states is less certain.
Is it a fact or a theory that cellular life has been around for half of that time? The evidence suggests that cellular life has been around for at least 3.5 billion years, and less convincing evidence exists for 3.8 billion years.
Is it a fact or a theory that multi-cellular life is at least 800 million years old? That multicellular life is at least 535 million years old is certain enough to be considered a fact, but the further back in time the claim, the less certain that claim can be. We do not know with any degree of precision whatsoever precisely when multicellular life began, and most likely there was an ambiguous period of time where arguments could be made either way for a collection of cells being simply a colony of single celled lifeforms versus an actual multicellular lifeform.
Is it a fact or a theory that major life forms now on earth were not at all represented in the past? This is one of the strongest facts of all within the field of evolution, and has also had a very strong influence on geology in the past by dating layers through indicator fossils (fossils unique to certain layers).
Is it a fact or a theory that there were no birds or mammals 250 million years ago? That would be considered a fact by most scientists.
Is it a fact or a theory that all living forms come from previous living forms? Excepting the origin of life, that's a fact.
Is it a fact or a theory that birds arose from non-birds? Of course. Just as you rose from non-you, species of one type arise from species of not that type.
Is it a fact or a theory that humans arose from non-humans? A fact. --Percy
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lyx2no Member (Idle past 4743 days) Posts: 1277 From: A vast, undifferentiated plane. Joined: |
Second, there are the observations that water freezes and boils at certain fixed temperatures (32F and 212F respectively) that provided us the Fahrenheit temperature scale.
? Kindly Ta-da ≠ QED
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