Can Vestigial Organs Constitute Evidence For Evolution?
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It's difficult to use vestigial organs as proof for evolution for two reasons.  1) You have to prove that a vestigial organ is, in fact, the remnant of some ancient organ, particularly an organ for which organisms would no longer have a need.  This is virtually impossible to do, as we have little information regarding the anatomy and physiology of prehistoric organisms. 2) You also have to prove that the vestigial organ is, in fact, a vestigial organ.  There are other examples of organs or appendages that were originally considered to be 'vestigial' and were then later found to have useful functions.  For example, the Vermiform appendix was originally considered to be a vestigial organ in mammals, but many scientists have shown that it may actually have a physiological role.  It's quite possible that all vestigial organs may have a role that we simply haven't discovered yet.  Many biologists have suggested that a vestigial organ be redefined as an organ that we simply don't understand.
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Many organisms possess vestigial structures that have no apparent function, but that resemble structures their presumed ancestors had. Humans, for example, possess a complete set of muscles for wiggling their ears, just as a coyote does (table 22.1). \n\nBoa constrictors have hip bones and rudimentary hind legs. Manatees (a type of aquatic mammal often referred to as "sea cows") have fingernails on their fins (which evolved from legs). Figure 22.17 illustrates the skeleton of a baleen whale, which contains pelvic bones, as other mammal skeletons do, even though such bones serve no known function in the whale. The human vermiform appendix is apparently vestigial; it represents the degenerate terminal part of the cecum, the blind pouch or sac in which the large intestine begins. In other mammals such as mice, the cecum is the largest part of the large intestine and functions in storageusually of bulk cellulose in herbivores. Although some suggestions have been made, it is difficult to assign any current function to the vermiform appendix. In many respects, it is a dangerous organ: quite often it becomes infected, leading to an inflammation called appendicitis; without surgical removal, the appendix may burst, allowing the contents of the gut to come in contact with the lining of the body cavity, a potentially fatal event.\n    \nThe skeleton of a baleen whale, a representative of the group of mammals that contains the largest living species, contains pelvic bones. These bones resemble those of other mammals, but are only weakly developed in the whale and have no apparent function.\n    \nIt is difficult to understand vestigial structures such as these as anything other than evolutionary relicts, holdovers from the evolutionary past. They argue strongly for the common ancestry of the members of the groups that share them, regardless of how different they have subsequently become. \nComparisons of the anatomy of different living animals often reveal evidence of shared ancestry. In some instances, the same organ has evolved to carry out different functions, in others, an organ loses its function altogether. Sometimes, different organs evolve in similar ways when exposed to the same selective pressures.
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Evolutionary arguments have been offered for male homosexuality. For example, Symons (1979) argues that homosexuality results from a meme that takes advantage of the inborn male propensity to find sexual variety interesting. Normally this propensity would be adaptive because it would encourage males to attempt sexual relations with many women, which would result in more offspring. But a meme could parasitize this propensity, redirecting sexual interest to non-adaptive objects, as in fetishism or homosexuality. \n\nEpigenetic arguments have been inspired by work on pre-natal hormones. Dîrner and his colleagues (cited in LeVay 1994) link stress during pregnancy to hormonal effects on the fetus that would lead to homosexuality. This could be part of a mother's adaptive reproductive strategy. That is, in times of stress, when it is difficult to raise children, it may be adaptive to have some homosexual children who could help their siblings raise offspring instead of having offspring of their own.\n\nMemic and epigenetic arguments may explain some aspects of homosexuality, such as the cultural variations in practices or identities, or specific behaviors of homosexuals (femininity for example). However, the biological studies of homosexuality, together with the extraordinary cross-cultural similarities of exclusive homosexuals (Whitam 1983) suggest that some aspects of homosexuality (e.g. orientation) are at least partly determined by genes.\n\nThe basic problem for genetic explanations of homosexuality is to account for how a gene that does not lead to offspring could survive the pressures of natural selection. One possibility is that a maladaptive gene for homosexuality might re-occur repeatedly in a population if it results from the frequent mutation of a gene that is normally adaptive. However, people with maladaptive genes rarely exceed 1% of the population, while male homosexuality apparently occurs much more frequently (Whitam and Mathy 1986; Gadpaille 1980; Diamond 1993). Another possibility is that a recessive gene for homosexuality might have advantages that allow it to pass on to future generations. For example, homosexuals could directly help their relatives (who share the recessive gene) raise more children. This "kin selection" hypothesis predicts more homosexuality in those societies where homosexuals could most help their relatives (for example, in endogamous societies where homosexuals would live nearby). Nevertheless, cross-cultural research shows that this is not the case (Werner 1979). Another possibility is that a homosexual gene itself, when combined with non-homosexual genes, may provide reproductive advantages. This latter scenario is sometimes known as the "heterozygous" hypothesis, although it is really about any type of gene combination (LeVay 1994; Sommer 1990). \n\nThe heterozygous argument suggests that homosexuality results from genes for submissive behavior. An animal possessing only submissive genes would fail to reproduce for lack of trying. But an animal possessing only genes for dominance would also fail to reproduce because it would get killed for taking too many risks. It is the "heterozygous" males, who would most likely pass on their genes. By the genetic laws of probability, this would leave every generation with a certain percentage of individuals at the extremes. For example, if each of a pair of chromosomes had only one "homosexual" locus with only two possible alleles (one for dominance and one for submissiveness) this would leave a heterozygous couple with 25% of their offspring homozygous for submissiveness, 50% heterozygous, and 25% homozygous for dominance. If, however, homosexuality were the result of the interaction of five gene loci, possibly spread across different chromosomes, then only 3.125% (1/22222) of births would be homozygous for submissiveness. As Wilson (1994) points out, some genetic diversity is valuable to individuals in t
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we don't even need fossils to prove evolution, we already have proof that things evolve. like the flu.  if the flu wasn't evolving then there would be only one vaccine for the flu. because it is evolving every year there is a flu shot (for those at risk) to the new strain.  people only object to evolution for religous reasons.  \n\n//\nin response to mr. onyxfire:  the reasons nominated for dissproving evolution seems to say that evolution should eliminate diversity.  and that simply isn't true. when there are alot of the same species in an area they compete for the same resources.  if a mutation came along that was different from that species it would actually be at an advantage because it might not be competing for the same resources.  and that is at the heart of diversity.  having diversity means that some animals will develope certain attributes more keenly for example people hunting for fruit during the day value eyesight more for finding their quarry where as at night bats looking for fruit can't rely on eyesight and so they develope a different specialized set of organs.  i hope that helps you understand why i think your points are incorrect\n&#92;&#92;\nno scientific theory which attempts to understand our world has by necessity precluded the concept of god.  none the less religous theories feel compelled to preclude any acceptance of science so it's my belief that they are quite the dumbasses (not all religious but certainly alot of the policy makers). we all know how well that galileo thing panned out for them.
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Here's the thing: I'm not an expert on fetal anatomy, but human fetuses do not have gills.  They do have tails for a few weeks, appearing around the 4th week and dispearing around the 8th.  They also have regions that are homolgous to those that develop into gills in aquatic organisms, but will form the throat of the human fetus.\n\nThe gill and tail myth was created by a man named Haeckel.  Now, Haeckel actually (whatever creationists may say) did have some good ideas, but he was a very bad scientist and had an unfortunate tendancy, especially in the later part of his career, to exagerate and even completely fabricate morphological features of embryos.\n\nHOWEVER, there _is_ an association between fetal development and evolutionary lineage.  It's just a bit more subtle than Haeckel claimed.  While embryos don't go through stages that ressemble the adult forms of their ancestors, the is a distinct correlation between the age at which the morphology of embryos of different species diverges and the evolutionary relationship between those species.  For example, human embryos and chimp embryos look really similar for a lot longer than human embryos and snake embryos.  But human and snake embryos look similar to each other long after they have completely diverged from the development of, say, a sea urchin.\n\nYour point about gills and tails isn't very accurate, and the actual connection between evolution and development is not very accesable to the non-scientist, but there is plenty of evidence for evolution that doesn't take a PhD to understand.  Here are a few points that I hope will help you next time you want to defend the theory of evolution:\n\n\n1. Vestigial structures\n\nOne example of a vestigial structure in humans is the appendix. It has no function. Removing it is harmful only in so far as any surgery is associated with certain risks (so I wouldn't have it removed just for fun, but it's because of the surgery not the absence of the appendix). An appendix is found in several mammals. In humans it is small and has no known function. In rabbits and many other herbivores it is large and is used in the digestion of cellulose.\n\nAnother example of a vestigial structure is the hipbones of snakes. Snakes evolved from quadrupeds, and some species still retain not on pelvises, but tiny protrusions of bone in a location that corresponds to the location of the legs in other quadrupeds.\n\n2. Microevolution can be observed in both a controlled laboratory setting and in nature.\n\nCreationists will tell you that microevolution does not prove macroevolution.  This is true.  However, it does provide evidence that macroevolution may be possible. Taken in the context of the other evidence for evolution, microevolution provides a mechanism by which macroevolution could occur. On its own, it doesn't prove that macroevolution occurs, but it does suggest that it is possible.\n\n3. The fossil record.\n\nAlthough the fossil record does not provide a “complete” record as fossils form only under certain conditions, it does show a gradual change in the morphology of species as well as numerous extinct species.  There are a number of methods used to date fossils, and the time period from which a fossil comes can be determined with reasonable accuracy.\n\n4. Imperfect structures (the blind spot of the mammalian eye, for example).\n\nI want to mention the bind-spot of the mammalian eye specifically because creationists often hold up the human eye up as an example of something that is too perfect to occur by "chance" (i.e. as the result of the natural selection of beneficial changes among random mutations).\n\nThere are also numerous examples where the morphology of a species is constrained by similar patterns in its ancestors (quadrupeds, vertebrates, etc.).\n\n5. Developmental biology reflects evolutionary lineage.\n\nCreationists like to bring up a man named Haeckel in response to this argument.
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Every fossil, every observation in biology points to evolution. There is nothing that goes against it or points to a different way to scientifically explain modern diversity. There is not one fossil or one piece of DNA that does NOT point to evolution.\nCreation relies on a lot of belief and the ability to dismiss all the known evidence, since ancient Greece to the present time, in the case for evolution.\nEvolution, on the other hand, keeps presenting solid evidence, regardless of those who believe otherwise. \n\nHere is a theoretical example of natural selection and adaptation.\n\nSay you have an island, about twenty miles from any other island, where there is a species of bird, say finches. In any population of birds, there is going to be a variety of beak sizes and wing sizes, (like nose and ear size, and height variation in humans), suddenly there was a drought, lasting several years, and the main food source of the finches, say, sesame seed, was destroyed, and all they had to eat was wheat, which is harder to break and eat than sesame. \nWhat characteristics would give one bird an advantage over another? Those with smaller beaks would have more difficulty cracking the wheat and feeding it to any baby birds, therefore they would have less live young. Those with largeer, stronger beaks would crack and eat more wheat and have more live young. Chances are, that their offspring would have, on average, larger, stronger beaks than those of small beaked finches. The stronger your beak, the more you eat, the more children you have. \nSo what other characteristics? Those with stronger, larger wings could try to find other food, but if they can't make to the other island, they die, those that make it to the other island, and if it has food, will have, on average, larger wings than those that didn't make it. They wil have more children, who, on average, will have larger wings.\nThese are simplified examples, it is more complex than this, but the basics are there.\n\nAnother, real life example is the Peppered moth.\nHere is the Wikipedia link\nhttp://en.wikipedia.org/wiki/Peppered_moth_evolution\n\nThis is evolution at work.\nRead more about evolution, but do it with an open mind. It wiil be of no use looking at evidence if you have already decided to reject it. Remember, you are doing science, at that is what scientist do. The more you read, the more you will understand. Try "Origin of Species " by Charles Darwin as a start, or try Google for a summary.\n\nGood luck to you.
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I'd like to think that you're asking this question with an earnest wish to get good informative answers. If that is the case, I invite you to see the link that Kurdiatcha left, or to do a web search for the term, or else, to read some good Evolution textbooks such as Ridley's "Evolution" or Freeman & Herron's "Evolutionary analysis", or Futuyma, or Stephen Jay Gould if you want something more entertaining.\nIf that is not the case, I'm not bothering anymore *sigh*
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"Evolution operates on several assumptions, the first being that there is no other way to explain how life got here without a god, so it must be true by default. "\n\nAbsolutely wrong.\n\n"Many people just say that the fossil record proves evolution, but they don't realize that it doesn't actually represent intermediates between two species but dead branches that became extinct."\n\nThe fossil record shows transitional forms, the kind that the theory of evoltuion predicts should have existed.\n\n"Modern humans did not evolve from neanderthals since they sometimes lived at the same time and place as other early humans, like you might see depicted in some drawings."\n\nTrue, but modern humans did evolve from a earlier primate ancestor that wasn't human.  Neanderthals are more like our cousins.\n\n"If changes can happen within species by chance, like different strains of bacteria, it also does not logically follow with absolute certainty that a single-celled organism can over millions of years evolve into more complex organisms and later evolve into a bird or a human. "\n\nBut the metabolic similarities, the universality of the genetic code, the fact that mitochrondria are in fact desceneded from bacteria, these are all best expained by common descent.\n\n"Not to say that it's wrong, but you can't prove something by inductive reasoning alone."\n\nEvolution is proved by the evidence.\n\nThe below links contain more than enough evidence to convince a reasonable person.
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Hundreds of thousands of fossil organisms, found in well-dated rock sequences, represent successions of forms through time and manifest many evolutionary transitions.\n\nBiogeography also has contributed evidence for descent from common ancestors.\n\nLots more info/evidence:\nhttp://newton.nap.edu/html/creationism/evidence.html
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We evolved from primates, but not monkeys specifically.  We did not evolve from birds although we do share a common ancestor with them a long ways back.  Although evolution has not been conclusively "proven" it is supported by a preponderance of evidence and accepted by the vast majority of the scientific community.  And hutsong's "evidence" against evolution is primarily fictitious.  Don't be fooled by his authoritative manner - he's still full of crap.\n\nFor a defense of evolution see my answer to this question:\nhttp://answers.yahoo.com/question/index;_ylt=AiUBrphbhCO3D7mQOX5JXrrsy6IX?qid=1006032117223\n\nAnd these links:\nhttp://www.txtwriter.com/backgrounders/Evolution/EVpage16.html\nhttp://evolution.berkeley.edu/evosite/lines/index.shtml\nhttp://fermat.nap.edu/html/creationism/evidence.html\n\nOr go to your local library and find an introductory biology book.
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An Evolutionary History based on Comparative Anatomy and fossil Sequences
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Homologous parts is about comparing *two* species (or male and female from the same species).\n\nTherefore only #2 is an example of homologous parts (as it is a comparison between dogs and humans).\n#1, 3, and 4 are examples of vestigial organs (or more correctly, 'vestigial structures' ... as sometimes the thing is so useless that it can't be called an 'organ' ... like the python leg bones).\n\nBy the way, some people might question whether human ear muscles are truly vestigial, because they are operational in some people (I can wiggle my ears).  However even if they work, it's hard to find a *purpose* for them, as is needed in other species to move ears for better hearing.  Similarly, some people claim that the human appendix sometimes serves some function for fighting infection.  However, the tailbone has no apparent function ... it's just a throwback to our embryology and ancestry.
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The male and female reproductive "tracts" are homologous.  This means that they're similar in structure and evolutionary origin, but are different in function.
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Yes it's a theory. Science itself refutes Darwinism. Science is disproving evolution more every day. There is less evidence for evolution today than there was when Charles Darwin first came up with the theory. There are a lot of scientists that don't believe in evolution, and more are changing their beliefs all the time. Here is a partial list of creation scientists (past and present).\nhttp://www.christiananswers.net/q-eden/edn-scientists.html\nWith all the evidence against it I really don't see how any open minded intelligent human being could believe in evolution. With the lack of proof for evolution it takes more faith to believe in evolution than it does to believe in creation and intelligent design. There is a lot more evidence for intelligent design than there is for evolution.\n\n* The Cambrian Explosion\nNearly all animal phyla made their first appearance in the fossil record at essentially the same time, an interval of some 5 million years (about 525 to 530 million years ago) called the "Cambrian Explosion.\n\nScientists have found that these early fossils exhibit more anatomical body designs than exist today, and that early animals, the trilobites, had eyes as fully developed as their counterparts today.\n\nMany of the Cambrian fauna, still survive today, all looking much like they did over 500 million years ago. The prominent British evolutionist, Richard Dawkins, comments, "... We find many of them already in an advanced state of evolution, the very first time they appear. It is as though they were just planted there, without any evolutionary history.\n\nTwo places in the world that have an abundance of early (Cambrian) fossils; the Burgess Shale in the Canadian Rockies and the Chengjiang site in China.\n\nIn Stephen J. Gould's popular book, Wonderful Life, he points out that the Burgess Shale Cambrian fossils include "a range of disparity in anatomical design never again equaled, and not matched today by all the creatures in the world's oceans.\n\nFurther, these fossils contain some twenty to thirty kinds of arthropods*** that cannot be placed in any modern group. The modern arthropods, consisting of almost a million species, can all fit into four major groups. But "one quarry in British Columbia, representing the first explosion of multicellular life, reveals more than twenty additional arthropod designs." Today there are about 38 phyla in existence, but the Canadian, Chinese and other Cambrian sites reveal over fifty phyla.\n\nThere has been a decrease in diversity (probably due to global catastrophes). This is the reverse of what evolutionary theory predicts.\n\nBesides diversity, the Burgess Shale shows exquisite detail, right down to "the last filament of a trilobite's gill," or the last meal in a worm's gut.\n\nThe Chengjiang site has even greater detail, and is earlier. According to Paul Chien, the chairman of the biology department at the University of San Francisco, said the preservation is such that internal organs, nerves, and even the water ducts of jellyfish are observable.\n\nResearchers found striking similarities between the compound eyes of the Cambrian trilobites and those of modern insects. According to Riccardo Levi-Setti, "Trilobites could see in their immediate environment with amazingly sophisticated optical devices in the form of large composite eyes. ... The number of individual optical elements in the compound eye could vary from approximately one hundred to more than fifteen thousand in a single eye, a range not very different from that found in modern insects.\n\nThe conclusion is that the eye, a complex visual system, was fully formed and functional extremely early in the fossil record. Obviously, this is not predicted by evolutionary theory.\n\nUntil recently, the phylum of vertebrates had been considered a later arrival in evolutionary history. But not now! Even the vertebrate phylum now extends into the Cambrian pe
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As a scientist, I try not to "believe" in something because it is appealing, but rather to consider the available evidence and use that information to reach a flexable conclusion that will change as additional information becomes available. Based on the available scientific evidence, I think it extremely likely that the principles underlying the theory of evolution are accurate. I therefore "believe" the theory of evolution, but not in the sense that one believes in God, but rather in the sense that I can assume it's true as necessary but I'm prepared to accept an alternate version of the theory or even to reject it if there is scientific evidence that is sufficient to warrent this change. \n\nHere's some of the evidence that supports the theory of evolution:\n\n\n1. Vestigial structures\n\nOne example of a vestigial structure in humans is the appendix. It has no function. Removing it is harmful only in so far as any surgery is associated with certain risks (so I wouldn't have it removed just for fun, but it's because of the surgery not the absence of the appendix). An appendix is found in several mammals. In humans it is small and has no known function. In rabbits and many other herbivores it is large and is used in the digestion of cellulose.\n\nAnother example of a vestigial structure is the hipbones of snakes. Snakes evolved from quadrupeds, and some species still retain not on pelvises, but tiny protrusions of bone in a location that corresponds to the location of the legs in other quadrupeds.\n\n2. Microevolution can be observed in both a controlled laboratory setting and in nature.\n\nCreationists will tell you that microevolution does not prove macroevolution.  This is true.  However, it does provide evidence that macroevolution may be possible. Taken in the context of the other evidence for evolution, microevolution provides a mechanism by which macroevolution could occur. On its own, it doesn't prove that macroevolution occurs, but it does suggest that it is possible.\n\n3. The fossil record.\n\nAlthough the fossil record does not provide a “complete” record as fossils form only under certain conditions, it does show a gradual change in the morphology of species as well as numerous extinct species.  There are a number of methods used to date fossils, and the time period from which a fossil comes can be determined with reasonable accuracy.\n\n4. Imperfect structures (the blind spot of the mammalian eye, for example).\n\nI want to mention the bind-spot of the mammalian eye specifically because creationists often hold up the human eye up as an example of something that is too perfect to occur by "chance" (i.e. as the result of the natural selection of beneficial changes among random mutations).\n\nThere are also numerous examples where the morphology of a species is constrained by similar patterns in its ancestors (quadrupeds, vertebrates, etc.).\n\n5. Developmental biology reflects evolutionary lineage.\n\nCreationists like to bring up a man named Haeckel in response to this argument.  Haeckel suggested that development reflects evolutionary origin.  It was later discovered that several of the sketches he used as evidence over-exaggerated certain features, and some were of different embryos all together. However, many of his sketches do accurately reflect the morphology of the embryo. Haeckel's methods were sometimes wrong and his ethics were poor, but it just so happens that his theory turned out to be fairly accurate.\n\nAny developmental biologist can tell you that embryos of related species show similar morphology in the early stages of development. The point at which their development begins to diverge shows a strong correlation with the relative point at which the evolution of the two species diverged. Human embryos look similar to chimpanzee embryos for a lot longer than they look similar to cat embryos, but all three develop similar structures in the
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The unnececery killing of any animal is a "murder". Never the less please allow me to add some comments.\n Evolution is a proven fact! There are more scientific evidence about Evolution and NONE about the Hebrew myth of creation! \nBiological evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations).\nDocumentation of ancestor-descendant relationships among organisms also comes from the fields of biogeography, taxonomy, anatomy, embryology and, most recently, genetics — particularly DNA analysis.\nThe fossil record remains first and foremost among the databases that document changes in past life on Earth. Fossils provide the dimension of time to the study of life. Some of the most basic observations about fossils and the rock record were made long before Darwin formulated his theory of “descent with modification.” The fossil record clearly shows changes in life through almost any sequence of sedimentary rock layers. Successive rock layers contain different groups or assemblages of fossil species.\n{We have now more than enough fossils to determine for sure that humans didn’t appear on this planet in the genetic form they are today!\nWE HAVE MORE THAN ENOUGH EVIDENCE THAT THERE WAS AT LEAST ANOTHER SPECIES WHICH LIVED WITH US!! And I am talking about Neanderthal man who was not our ancestor but a different Human than us!!! (Did God experiment with human species?) We even have proof that at a certain point in time 3 human species shared the planet! (Homo sapiens, Homo Erectus, Homo Neanderthals)}\nOf course I want comment the stupid argument why all the apes didn’t evolve to humans. Ok I will comment!!\n(We share a recent common ancestor with chimpanzees and gorillas; we have many anatomical, genetic, biochemical, and even behavioral similarities with these African great apes. We are less similar to the Asian apes--orangutans and gibbons--and even less similar to monkeys, because we share common ancestors with these groups in the more distant past!\n By the way why God decided to create 5 different species of primates and 280 different species of monkeys?)\nAs a conclusion Evolution is not a theory but a proven fact (In scientific terms, "theory" does not mean "guess" or "hunch" as it does in everyday usage. Scientific theories are explanations of natural phenomena built up logically from testable observations and hypotheses. Biological evolution is the best scientific explanation we have for the enormous range of observations about the living world.) Creation is a Hebrew Myth and unfortunately is not a fact but a myth!!!!
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I think the fossil record is the most convincing evidence we have for evolution.  Granted, it does have a few holes, but the holes aren't nearly as large as the holes in the Bible.  \n\nAnd as far as the comment made by Stand goes - evolution is such a slow process.  Just because we don't see evolution occurring, doesn't mean it's not going on behind the scenes.  I have heard some arguments that evolution of humans has stopped because we don't have the environmental pressures we used to - we use technology to ensure that "everyone" survives.  This is somewhat ludicrous, however, because this theory comes from the point of view of a person living in a first world country.  What about the billions living in third world countries?  Do they have the advantages of technology?  Also, what about the other forms of selection, such as sexual selection?  Truth be told, there are approximately 4.2 "important" amino acid mutations per generation, and since the technical definition of evolution is 'the change in the gene pool of a population over time', we are definitely still evolving - just not in visible ways.  Yet.