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Member (Idle past 1969 days) Posts: 6165 From: Co. Wicklow, Ireland. Joined: |
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Author | Topic: Where are all the missing links? | |||||||||||||||||||||||||||
iano Member (Idle past 1969 days) Posts: 6165 From: Co. Wicklow, Ireland. Joined: |
I wasn't looking to get into serious debate about this but had a question about Evolution. I hope the 'Coffee Shop' is the appropriate place to pose it.
A I understand it, ToE says we evolved from lesser animals. The basic mechanisms are 'genetic mutation' which provide diverse 'options' and 'survival of the fittest' which culls the less suitable options to leave one or a few successful options which survive to propagate the successful genes. Repeat for millions years to get the diversity we have today. From what I gather, folk who say evolution didn't happen point to the lack of definitive 'transistional' or 'link fossils' in amongst the millions of fossils already found. The argument seems to be that many fossils should display obvious signs of developing into something else whereas most seem to be perfectly formed for the task at hand.'Archeaopteryx' is posed as an example of the 'link' between reptile and bird, but it's very rarity as a 'find' and the fact it is much-debated seems to illustrate the apparent problem, ie: such 'demonstrable' links seem to be a relative rarity whereas we could expect there to be many of them. Flight of any description would have been a major boon and presumably such a creature would have done very well. Is there a flush of fossils indicating this boon and if not, why not. Generally speaking, has there been a rarity of obvious link-fossils with a tentitive but workable toe in it's history or future (it would seem 'sensible' to hang on to your former function until the new advantageous function was in some way operational ). If so, why is that? This message has been edited by iano, 09-Aug-2005 12:22 PM
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CK Member (Idle past 4156 days) Posts: 3221 Joined: |
quote: I don't see the point of having this debate outside the science forums, it just gives people a licence not to back up their claims - in fact the whole thing looks like an endrun.
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AdminSylas Inactive Member |
Good catch, Charles. I'll move it into Proposed New Topics. That's the right place to propose a discussion like this.
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AdminSylas Inactive Member |
Thread moved here from the Coffee House forum.
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AdminSylas Inactive Member |
Thread moved here from the Proposed New Topics forum.
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Nuggin Member (Idle past 2521 days) Posts: 2965 From: Los Angeles, CA USA Joined: |
Quote:
Flight of any description would have been a major boon and presumably such a creature would have done very well. Is there a flush of fossils indicating this boon and if not, why not. There are in fact a lot of fossils coming out of China at the moment that show many different animals with various flight / feather characteristics. The reason so many are coming from one area is the extraordinary luck (good for us, bad for them) of a volcanic eruption spewing fine ash and preserving the animals with such detail that we can actually see the feathers. Feathers, by the way, serve as a great indicator for evolution. Only birds have feathers today, but the fossil record shows species with both feathers and "lizard-like" features. Teeth for example. As for your other question - "where are all the missing links?" They are there, but it all depends on who you are talking to. I'm going to use numbers to make myself clear. Say an early species is a 1 and a modern decendant is a 10. If we are lucky we might find 1, 2, 4, 5, 8 and 9 in the fossil record. Where is 3? Maybe we haven't found it yet. Maybe it didn't exist for a very long period of time, or there weren't many of them, or it just didn't die in the right place to get fossilized. But not having #3 does not detract from the fact that we have the others and that the pattern is clear. What anti-Evolution people like to say is this: "Yeah, you have all those, but where's the missing link between 1 and 2?" Then someone will discover 1.5 and they say, "Okay, but where's the one between 1 and 1.5?" "Where's the one between 1.25 and 1.5" etc It doesn't end. No matter how many examples you find, there is always one in between two that you have. It sounds like they literally want every single skeleton of every species over a 300 million year period before they'll agree there is proof.
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Glordag2 Inactive Member |
quote: I'd like to add to this by mentioning that it's not as much a "1-10" scale as a "1-1000+" scale. Basically, it's going to take more than 10 transitions to get a drastic change (reptile to bird, for instance). The problem is that fossils actually aren't as prevelant as you (the OP) made them sound. There certainly aren't millions of fossils for any particular chain you look at (a particular reptile to a bird, for instance). There are actually very few. This makes it incredibly hard to find fossils for every single step in an evolutionary process in which there could be thousands of these so-called "steps". The reason that we might have lots of fossils of one species of something as compared to others is mostly a result of location and natural occurances. If something is covered away and protected from weathering, it is going to have a greater chance of producing a fossil than something else (like the ashes Nuggin described). Some of these occurances can happen quite often in an area, preserving fossils for everything in that area but not in other areas around it.
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Chiroptera Inactive Member |
quote: Which is a bad argument. Of course all known species are "perfectly formed for the task at hand" -- if they weren't, they would not have survived. Evolution must proceed through species that are "perfectly formed for the task at hand". -
quote: The very first specimen of Archaeopteryx was originally classified as a new species of dinosaur and put into a drawer and forgotten for a over a hundred years. It was only when the second specimen was discovered with very clear feather impressions that its bird nature was realized. If that doesn't scream "transitional" then I don't know what does. -
quote: Well, the apparent problem is that some people are set in their beliefs are simply going to deny anything that contradicts them. -
quote: Why should we expect to see "many" of them? I would expect to see very, very few...and am pleasantly surprised that we have as many that we do. -
quote: Flight itself is not going to pop into existence all at once. There are going to be intermediates on the path to flight which will not be flying creatures. These intermediates will have to have some sort of feature that is "perfectly formed for the task at hand" and yet be the type of feature that will be able to evolved further into wings. It is possible that these in-between states survived in relatively small niches. And even then, it is not automatically guaranteed that the species will continue to evolve into flying creatures -- evolution does not proceed with a goal in mind. It is possible that the in-between "gliding" features (like the flying squirrel?) may be such that no further evolution into wings is possible. It may be that further generations will exhibit other characteristics that ensure survival that will take the species down another path, away from flying. But it does seem that flying is a boon once established. Insects, especially beetles, are the most ubiquitous group of animals known. Birds are also very successful. Among mammals, the most successful order is *ahem* Chiroptera, the bats.
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deerbreh Member (Idle past 2921 days) Posts: 882 Joined: |
How likely is that flying (gliding) squirrels could ever develop full fledged flight? Is it possible that many flying animals had transitional gliding forms? Also I would point out that even birds that are fully capable of flight are quite fast at running as well and will actually run rather than fly if the terrain and circumstances allow it. A ring-necked pheasant is one example. So flight developed even as other forms of locomotion remained quite functional.
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Chiroptera Inactive Member |
Bats, flying lemurs, and primates share a common ancestor that they do not share with any other group. So it is probably a safe bet that the non-flying ancestor of bats were arboreal, and so flying probably developed from a gliding transitional form. In fact, the flying lemur is a "flying squirrel" type of glider.
As far as birds, I don't know. I know I have seen pictures of the feathered ancestor of birds as arboreal, but I don't know whether there is direct evidence for this or whether it is a guess of the artist. At any rate, I assume that the non-flying ancestor of birds was arboreal and bird flight arose from gliding -- however, I admit this is just because I find it easier to imagine flight arising this way. But you are right -- unless some new finds have been discovered that have shed light on this, it is still a matter of conjecture why wings originally developed in birds. By the way, interesting fact -- molecular evidence suggests that two main groups of bats, the megachiroptera and the microchiroptera, are not monophyletic, and that these two lines may have developed flight independently.
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Rahvin Member Posts: 4046 Joined: Member Rating: 7.4 |
I was hoping this topic would get promoted.
The "missing link" idea is a flawed understanding of what the Theory of Evolution actually states. Technically speaking, every species is "transitional," being between its ancestors and descendants. Transitional species are literally all around us. Let's start with fossilization. Very few dead organisms become fossilized - it's an incredibly rare event, and we are truly lucky to find many of them at all. We can hardly expect to find a complete family tree leading directly from one organism through gradual changes over generations until a new species is formed - fossilization is just too rare to reasonably expect such a thing. With humans, Creationists tend to ask for a "missing link" between man and ape, assuming that we should be looking for some mix-and-match half-ape, half-man creature. This is a false assumption. We have already seen several species which appear to have evolved from our common ancestor. Creationists say that these species are simply "another species of ape," but that's the point. We have several examples of ape-like creatures gradually attaining more human-like features (standing upright, etc.). The fact that we don't have a fossilized example of every single generation in between does not invalidate the theory that humans evolved from an ape-like common ancestor. For other species, we can sho a gradual change over time. Archeopteryx, while a "rare find," still shows an obvious link between birds and disosaurs. Most dinosaurs wer practically birds anyway - many species had bone structure (specifically the shape of the hips) identical to that of birds, while others still resembled reptiles. The fossil record also shows an excellent evolutionary path for horses gradually evolving from rodent-like mammals. Now lets move on to modern species. Only bacteria and the like will actually give us true observational results (as in, directly watching the strain change over generations), because of their rapid reproduction, but we can also see the effects of evolution in the various species of animals on the planet today. Let's start with the Bombardier Beetle. For those who don't know, this beetle has the remarkable adaptation of being able to literally shoot a chemical spray at a predator. It has an internal combustion chamber with just the right combination of chemicals, enzymes, an inhibitor chemical, and a tough chamber wall to allow it to "fire" its biological cannon without exploding itself. Creationists point to this species often as "irreducibly complex" becuase, if the exact composition of the biological cannon are altered in any way, the insect would either blow up (not great for evolution, obviously), or simply not fire. Obviously this creature must have been created fully formed. What the Creationists fail to realize, however, is that there are other species of beetle closely related to the Bombardier who have the exact same chemicals present in their bodies. They are used for entirely different purposes, but the similarities show that they have a common ancestor, and that the Bombardier simply evolved in such a way that the species is able to use those same chemicals for a vastly different purpose. The similarities between multiple species is commonplace. There are similarities in bone structures (the spinal columns of man and ape, for instance), behavioral similarities (bee species on different continents who have the same behavioral patterns), biochemical similarities (human blood-precipitation agents are still 64% effective in gorillas), and even the embryos of vastly different species look nearly identical. Next we have various organs. Some organs are vestigial in some creatures and fully functional in others. For instance, the human appendix is basically a useless liability, and we remove it if issues arrise with no change to our body functions. It's an "evolutionary leftover" that our ancestors used but we no longer require. Other organs have different uses in related species. Most insects have two pairs of wings, but flies differ in that they only use one pair for flight - the other pair is still there, but is used for stability instead. Many fish have organs that produce a small electric charge that they use for navigation, while others have the exact same organ that can produce a much stronger charge and give predators a nasty shock. All of this is evidence of species transformation. All of these features likely had a common ancestor, and the descendants branched out using the organ for different purposes. The "missing links" to species are literally all around us. Related species can have identical features that have different uses. Organisms often have organs useful to more primitive relatives, but are no longer usefull or needed in the "more advanced" species. Structural similarities over a wide base of related species show common ancestry. We see the evidence for evolution every single day. If evolution did NOT happen, what accounts for these similarities? Why would one organism have an organ necessary for its survival, and another organsim that looks similar have a nearly identical organ that is not necessary and is in fact a health risk? The fossil record is only a small part of the evidence for evolution, yet it supports the theory in every way. Modern species show evidence all around us of features and organs gradually evolving across multiple related species, and finding different uses or no use at all while still remaining present. With all of this evidence, and more, Creationists still point to "transitional species," saying that these similarities are irrelevant - they are not a clear "in-between" form. This is based on a false understanding of evolution,. This isn't X-Men or Teenage Mutant Ninja Turtles, we aren't looking for Bigfoot, and other popularized examples of evolution (like a few episodes of Star Trek) have no basis in reality. We aren't going to find every single generation in between two species because fossilization is so rare, and we aren't looking for Chimaera-like half-breeds. When the evidence is actually examined in light of the actual predictions of Evolutionary Theory, the evidence clearly supports common ancestry, and gradual changes over time guided by natural selection. Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.
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Chiroptera Inactive Member |
quote: To be honest, though, this hip feature does not really count as a link between birds and dinosaurs since birds actually arose in the reptile-hip branch -- bird-like hips arose independently among the bird-hip dinosaurs and birds themselves. (Unless, of course, bird-hips are found among the saurischian theropods from which the birds arose.)
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Rahvin Member Posts: 4046 Joined: Member Rating: 7.4 |
To be honest, though, this hip feature does not really count as a link between birds and dinosaurs since birds actually arose in the reptile-hip branch -- bird-like hips arose independently among the bird-hip dinosaurs and birds themselves. (Unless, of course, bird-hips are found among the saurischian theropods from which the birds arose.) Either way, they have great similarity in their bone structures, and it seems readily apparent that one evolved from the other. Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.
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Chiroptera Inactive Member |
Oh yes indeed. I was just quibbling.
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arachnophilia Member (Idle past 1372 days) Posts: 9069 From: god's waiting room Joined: |
How likely is that flying (gliding) squirrels could ever develop full fledged flight? Is it possible that many flying animals had transitional gliding forms? there's some debate over the functionality and purpose of feathers originally. the "gliding" hypothesis is not generally accepted by everyone. for instance, feathers appeared to have developed first in small gournd-based theropods for warmth and/or display. flight seem to have developed from the ground up, so to speak.
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