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Author | Topic: Convergent Evolution - Reasonable conclusion? or convenient excuse? | |||||||||||||||||||||||||||||||||||||||||||
BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
As requested by Taq in Message 147 of Biological classification vs 'Kind', this thread is for the examination of case studies in convergent evolution to demonstrate the validity (or lack thereof) of the independent evolution of similar structures.
My assertion: Convergent evolution is a convenient way for darwinists to explain exceptions to the supposed nested hierarchy that forms the phylogenetic tree. When similar structures are detected in different clades darwinists rationalize it away as convergent evolution - instead of making the more reasonable conclusion that not all life fits into a neatly nested hierarchy of traits. As an initial case study for discussion, consider echolocation in bats and dolphins. According to this January 2010 Science Daily article both bats and dolphins share almost identical genes for echolocation. The statistical odds of the exact same mutations being selected in both species to form a working echolocating sense is nearly impossible - yet according to this research this seems to be the case. Wouldn't a much more reasonable conclusion be a common Designer re-using a created feature? I don't see anyone claiming recent common ancestry between bats and dolphins - yet genetic similarities of the same sort are used to show common ancestry between humans and chimpanzees. Why draw a conclusion of common ancestry for one case but not the other? Or is the data simply inconvenient because it doesn't fit the darwinian model? Edited by BobTHJ, : fix tag error
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: You are correct. I needed to brush up on my genetics and misinterpreted this article initially. I agree that the selection of certain amino acids are far more likely than the selection of specific nucleotides.
quote: Statistics is not my strong point - and I shouldn't have made a sweeping general assertion as to the odds in question - but let's see if I can take a stab at it: 20 base amino acids14 convergent sites So, the base odds are 20^14, correct? Of course, selective pressure would reduce this by eliminating deleterious mutations over time. I recall reading recently that studies have shown approx. 70% of mutations to be deleterious. Selective pressure isn't fool-proof by any means, but for the sake of a conservative estimate let's assume that it eliminated all 70% of deleterious mutations - leaving only neutral or beneficial mutations remaining. That gives us final odds of 1 in 4.9152 10^17 which is still overwhelmingly improbable - or am I missing here? Edit: Oh, and this doesn't take into account mutations that would disable the gene - such as new stop codons. Edited by BobTHJ, : noting gene disabling mutations
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Agree with your second sentence. However, this doesn't explain how both bats and dolphins independently developed a protein sharing the specific formatting required to make it sensitive to high frequencies - and yet other mammals did not.
quote: Agree. The problem becomes: how do you make the determination? How do you decide between "This similarity is a result of common ancestry" and "This similarity is the result of convergent evolution"? I'm still convinced the answer is "Which better fits our neatly organized phylogenic tree?"
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Were I a darwinist attempting to assemble a phylogenetic tree then I agree with this assessment. However, as I mentioned in my previous post, where do you draw the line? Not all traits fit neatly into a nested hierarchy.
quote: The overall evidence for a nested hierarchy is not high - the many cases of 'convergent evolution' demonstrate this. What does have a lot of evidence is the conclusion that creatures with similar morphological features will share similar genes. However, this conclusion does not support common ancestry and more than it supports baraminology.
quote: This does nothing to prove or disprove common ancestry - all it demonstrates is that there are multiple methods of expression for any particular outcome - the genetic code has told us this for quite some time.
quote: I would not dispute this statement.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: I agree with the gist of this - and yes, were the prestin substitutions the only similarity then it might be feasible (though still improbable) that echolocation were to evolve convergently in separate species. But consider that both classifications would also need to separately evolve enhanced cochlea and a high-frequency sound emission system and we're suddenly increasing the complexity and subsequent odds substantially - even if the genetics may look different. Also, look at the inverse: if selective pressure for prestin is so high then why have not all mammals evolved the enhanced prestin of dolphins and bats? I have a hard time picturing a situation where hearing higher frequency sound wouldn't be an increase in fitness.
quote: Thanks for the NCBI link....I didn't realize that stuff was available online for free
quote: No....common ancestry would imply a close genetic makeup.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: So, is your viewpoint: we can't really figure out a good statistic, so we'll just assume it happened?
quote: Yes, I'm sorry. I meant to say non-synonymous mutations are 70% deleterious - which is what fits with my math.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Thank you, I appreciate the comprehensive reply!
quote: I haven't looked, but it is probably safe to assume that the vast majority of these species are the result of recent variation (we may define 'recent' differently, but suffice it to say that they have very close relatives) so it seems your figure should be substantially less. I also doubt that the wikipedia article is comprehensive in nature as I've seen mentions of several hundred or more cases of convergency. As a result it is likely the percentage is substantially higher than .005%. As I stated in another thread - I suspect the phylogenetic tree to be a 95%+ accurate categorization of living organisms (ontology only - no common descent implied) - with these non-conforming cases composing the other <5%. Just stating this for the record so everyone knows where I stand.
quote: Yes - and that seems to be what happens. Organisms are placed into the phylogenetic tree at the location where they show the most similarity to the surrounding organisms. This reflects a good ontology model - though it does lead to some inconsistency since some organisms classed in different clades still share similarities not shared by other closely classed organisms.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Does ID have something to account for or explain? Convergence is a (potential) problem for common-ancestry evolution, not ID. The common Designer readily explains any convergence under ID.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Let me clarify - as I really botched it earlier. 95%+ of organisms fit nicely into a nested hierarchy. However, the hierarchy can not fully model that last <5% because there will be shared features/genes with other not closely grouped organisms. And, though I've posted it elsewhere I'll restate it here for completeness: nested hierarchy does not imply common ancestry - only a semi-reasonable ontological model.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: And I can not. In hindsight I started this topic without first doing the appropriate research to educate myself. I apologize to everyone. I'll add this to my growing list of topics to research in-depth. In the end here though I am accomplishing my goals for joining the discussion at this site. I'm learning a lot about science - including how to coherently defend my conclusions. I'm also learning about some areas where those conclusions seem to fall flat - so I will dig deeper into learning about those topics to see if my conclusions are unfounded. Thanks to all of you for assisting me in this endeavor.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Common design is evident in all aspects of our universe - from the atomic to the astronomic. Grouping by similarity occurs at various levels in Biblical contexts as well. Cases of common morphology without common genetics does not make common design an unreasonable conclusion.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: If we failed to find significant similarity between life forms it would evidence against a common designer.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Of course - if organisms lacked significant similarity to each other then you would have evidence against common design. For example, if organisms didn't share a similar cell structure but instead most used a basic anatomical unit that was different from other organisms this would be evidence against common design. Or if organisms didn't all use DNA/RNA but instead each used its own method of storing data - that would be evidence against common design. Both are fairly reasonable conclusions - they both fit the data.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Of course. You disagree with my opinion that the phylogenetic tree correctly models similarity (both morphological and genetic) to a degree higher than 95%? I didn't think many people would fight me on that assumption.
quote: Sure, echolocating in bats and dolphins. They are not classed together in the phylogenetic tree (nor should they be if you want the most accurate ontological model possible) yet share a similarity not shared by other closely grouped organisms.
quote: A high degree of correlation between genomes and morpholocial features fits well with a design hypothesis. Just because darwinian evolution fails without that correlation doesn't mean it is the more reasonable conclusion.
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BobTHJ Member (Idle past 5028 days) Posts: 119 Joined: |
quote: Hmm...you see this as evidence for evolution. I see this as those who wish to deny the existence or involvement of God* devising the most reasonable naturalistic explanation to explain His creation. Not at all unlikely. *And because I know it's coming - no I'm not implying all evolutionists are atheists.
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