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Author Topic:   Convergent Evolution - Reasonable conclusion? or convenient excuse?
Dr Jack
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Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
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Message 16 of 107 (564302)
06-09-2010 5:10 PM
Reply to: Message 15 by Taq
06-09-2010 4:47 PM


Re: A good case study
What you need in order to do the statistics is the population sizes, mutation rate, time period in which these mutations occurred, and the percent increase in fitness conferred by each mutation.
And consider that this example has been picked out precisely because of its remarkable feature.

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BobTHJ
Member (Idle past 4998 days)
Posts: 119
Joined: 06-02-2010


Message 17 of 107 (564305)
06-09-2010 6:12 PM
Reply to: Message 8 by Asking
06-07-2010 12:21 PM


quote:
With these points in mind its innevitable that we should find similar genes in bats and dolphins. Given the nature of this gene it would be suprising if we'd found that there was a significant different between them.
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:
Of course there is an important lesson to be learned from this research and that is that when determined how related various species are from their genes care should be taken in interpretation of results. Of course this is already addressed as they don't just rely on one gene to make these phylogenetic tree's.
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 4998 days)
Posts: 119
Joined: 06-02-2010


Message 18 of 107 (564306)
06-09-2010 6:31 PM
Reply to: Message 9 by Peepul
06-07-2010 12:52 PM


quote:
The nested hierarchy is deduced by looking at lots of traits - looking at one will give odd results.
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 strength of the argument for a nested hierarchy is very high - that's why scientists don't overturn it in the face of examples of convergence. It's supported by a large number of statistically significant studies of relationships based on morphology and / or genetics.
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:
Changes are happening now to our understanding of convergence, as genetic data overturns some previous thinking based on morphology. The genetics gives a better picture of what is truly convergent. Features that are based on different genetics but look similar are clearly convergent - and there are examples of this.
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:
This isn't always the case of course, but this kind of result does demonstrate that at least some convergence is only phenotypic.
I would not dispute this statement.

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Wounded King
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Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 19 of 107 (564309)
06-09-2010 6:38 PM
Reply to: Message 13 by BobTHJ
06-09-2010 3:57 PM


Re: A good case study
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
These sort of calculations are notoriously unreliable and massively sensitive to initial assumptions.
For a start, as I mentioned previously, it isn't the case that any one dolphin-bat pair actually shows all 14 convergent amino acid substitutions.
So, the base odds are 20^14, correct?
Almost certainly not. If we assume that there is an original ancestral Prestin sequence then we need to calculate the odds of the specific changes from that sequence, not the odds of a particular set from of a random assortment of 14 selections from a pool of 20 possible amino acids.
Some amino acid changes are simpler than others and because nucleotide substitutions are not completely random, in that certain changes are more frequent than others, certain amino acid substitutions will also be more frequent and therefore more likely to occur.
I recall reading recently that studies have shown approx. 70% of mutations to be deleterious.
I'm not really sure why you feel these figures are particularly relevant. For a start we don't even have a per site mutation rate for the Prestin gene, so the proportion that will be deleterious is somewhat irrelevant. I'm also a bit dubious of the 70% figure, the vast majority of mutations are neutral, in a coding gene this is different but I still find the 70% figure unlikely. The first thing I found sounding similar to this was the wikipedia article on mutation which gave 70% as the figure for deleterious mutations from mutations causing non-synonymous amino acid substitutions.
I'm also not sure why you want to treat deleterious mutations as distinct from null or disabling mutations.
As I said these sort of calculations are essentially pointless.
TTFN,
WK

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Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 20 of 107 (564312)
06-09-2010 7:11 PM
Reply to: Message 18 by BobTHJ
06-09-2010 6:31 PM


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.
You seem to have already forgotten the point we discussed earlier about the appropriate level for convergence that was relevant to casting doubt on modern evolutionary theory being the genetic level. Almost all of the examples in that list are of convergent morphology, which is by no means the same as convergent genetics. If you feel you can make a case that morphological convergence between mammals and marsupials, for example, is due to genetic convergence then feel free. Many of these cases directly contradict your assumption that convergent morphologies rely on convergent genes. Convergent morphologies or functions can arise from totally distinct genetic sequences or complements.
There are only 7 examples for enzymes or biosynthetic pathways and even in those cases there is no evidence of genetic convergence.
TTFN,
WK

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 21 of 107 (564317)
06-09-2010 7:55 PM
Reply to: Message 18 by BobTHJ
06-09-2010 6:31 PM


superficial similarity but differences in the details
Hi BobTHJ, and welcome to the fray.
Just a small point or two.
The overall evidence for a nested hierarchy is not high - the many cases of 'convergent evolution' demonstrate this.
Do you know how many different species are currently living? This list is less than 1% of the NEW species recently added to the catalog of life:
Number of Earth's species known to scientists rises to 1.9 million | Wildlife | The Guardian
quote:
The number of species on the planet that have been documented by scientists has risen to 1.9 million, according to the world's most comprehensive catalogue of plants and animals.
The new figure has been boosted by 114,000 new species discovered since the catalogue was last compiled by Australian researchers three years ago — a 6.3% increase.
And evidently we still don't know all of them.
While there are only 100 instances listed in the wiki article, and I don't call 100/1.9X10^6 = 0.005% a significant problem.
What does have a lot of evidence is the conclusion that creatures with similar morphological features will share similar genes.
Which is why, when you look at the details for animals that appear similar at the gross level, they show convergent evolution from different branches of life.
One from your - actual wiki's - list is the thylacine and wolf:
quote:
The skulls of the Thylacine (left) and the Grey Wolf, Canis lupus, are almost identical, although the species are only very distantly related (different infraclasses). The skull shape of the Red Fox, Vulpes vulpes, is even closer to that of the Thylacine.[1]
If you look closely you will see differences in each picture that are due to different hereditary ancestry. These differences are why biologists know that this is a case of convergent evolution.
We had a thread here a while ago that went into detail on the actual anatomical differences between these two organisms, and this showed that the basic detail level (number and type of teeth for instance) the characteristics of the thylacine were closer to the other marsupials than to the placental mammal wolf and that the grey wolf were closer to other placental mammals than to the marsupial thylacine.
Unfortunately the last time I checked for it, it appeared that the photos were no longer showing (the links were not working).
Curiously, the nested hierarchies of animals based on their morphological traits put these two animals in different clades, the grey wolf with the placental mammals and the thylacine with the marsupials, because of the morphological details.
We see similar detail differences in sugar-gliders and flying squirrels (also on the list):
When we look at the details once again, we see that the sugar-glider is clearly a marsupial and the flying squirrel is clearly a placental mammal, and these detailed differences are what the nested hierarchies are based on.
The same holds for the other organisms on this list.
However, as I mentioned in my previous post, where do you draw the line? Not all traits fit neatly into a nested hierarchy.
Where you draw the line is based on the preponderance of evidence at the detail level.
Interestingly, the same kind of nested hierarchy can be formed from genetic information, and if evolution is not the correct explanation, then there is no reason for a genetic hierarchy to match the one developed on the morphological details.
Fascinatingly, these two versions of nested hierarchies agree to phenomenal levels of comparison with very little error.
However, this conclusion does not support common ancestry and more than it supports baraminology.
Amusingly you don't show how "it supports baraminology" but just make an unfounded assertion.
Enjoy

I counted the list by changing the bullet to numbers by global substitution. The thylacine is #3 and the sugar-glider is #9.
Many items on this list are only specific traits (see opposum opposable thumb) rather than whole organisms.
List of examples of convergent evolution - Wikipedia
  1. The pronghorn antelope of North America, while not a true antelope and only distantly related to them, closely resembles the true antelopes of the Old World, both behaviorally and morphologically. It also fills a similar ecological niche and is found in the same biomes.
  2. Members of the two clades Australosphenida and theria evolved tribosphenic molars independently.
  3. The marsupial thylacine (Tasmanian Tiger) had many resemblances to the placental canids.
  4. Several mammal groups have independently evolved prickly protrusions of the skin — echidnas (monotremes), the insectivorous hedgehogs, some tenrecs (a diverse group of shrew-like Madagascan mammals), Old World porcupines (rodents) and New World porcupines (another biological family of rodents). In this case, because the two groups of porcupines are closely related, they would be considered to be examples of parallel evolution; however, neither echidnas, nor hedgehogs, nor tenrecs are close relatives of the Rodentia. In fact, the last common ancestor of all of these groups was a contemporary of the dinosaurs.
  5. Cat-like sabre-toothed predators evolved in three distinct lineages of mammals — sabre-toothed cats, Nimravids ("false" sabre-tooths), and the marsupial "lion" thylacosmilus. Gorgonopsids and creodonts also developed long canine teeth, but with no other particular physical similarities.
  6. A number of mammals have developed powerful fore claws and long, sticky tongues that allow them to open the homes of social insects (e.g., ants and termites) and consume them (myrmecophagy). These include the four species of anteater, more than a dozen armadillos, eight species of pangolin (plus fossil species), the African aardvark, one echidna (an egg-laying monotreme), the enigmatic Fruitafossor, the singular Australian marsupial known as the numbat, the aberrant aardwolf, and possibly also the sloth bear of South Asia, all not related.
  7. Koalas of Australasia have evolved fingerprints, indistinguishable from those of humans. Apes' fingerprints are very similar to those too.
  8. The Australian honey possums acquired a long tongue for taking nectar from flowers, a structure similar to that of butterflies, some moths, and hummingbirds, and used to accomplish the very same task.
  9. Marsupial sugar glider and squirrel glider of Australia are like the placental flying squirrel.
  10. The North American kangaroo rat, Australian hopping mouse, and North African and Asian jerboa have developed convergent adaptations for hot desert environments; these include a small rounded body shape with very large hind legs and long thin tails, a characteristic bipedal hop, and nocturnal, burrowing and seed-eating behaviours. These rodent groups fill similar niches in their respective ecosystems.
  11. Opossums have evolved an opposable thumb, a feature which is also commonly found in the non-related primates.
  12. Marsupial mole has many resemblances to the placental mole.
  13. Marsupial mulgara has many resemblances to the placental mouse.
  14. Planigale has many resemblances to the deer mouse.
  15. Marsupial Tasmanian devil has many resemblances to the placental wolverine.
  16. Kangaroo has many resemblances to the Patagonian cavy.
  17. The Marsupial lion had retractable claws, the same way the placental felines (cats) do today.
  18. Microbats, toothed whales and shrews developed sonar-like echolocation systems used for navigation and for locating prey. DNA study has shown that echolocation in two types of bats, megachiroptera and microchiroptera, came about independently.
  19. Both the aye-aye lemur and the striped possum have an elongated finger used to get invertebrates from trees. There are no woodpeckers in Madagascar or Australia where the species evolved, so the supply of invertebrates in trees was large.
  20. Castorocauda and beaver both have webbed feet and a flattened tail, but are not related.
  21. Prehensile tails came in to a number of unrelated species New World monkeys, kinkajous, porcupines, tree-anteaters, marsupial opossums, and the salamander Bolitoglossa pangolins, treerats, skinks and chameleons.
  22. Pig form, large-headed, pig-snouted and hoofs are independent in true pigs in Eurasia and Peccary and Entelodonts.
  23. Plankton feeding filters, baleen: Whale sharks and baleen whales, like the humpback and blue whale independent have very sophisticated ways of sifting plankton from marine waters.
  24. There are five species of river/freshwater dolphins, which are not closely related.
  25. Platypus have what looks like a bird's Beak (hence its scientific name Ornithorhynchus), but is a mammal.
    [edit] Dinosaurs
  26. Ornithischian (bird-hipped) dinosaurs had a pelvis shape similar to that of birds, or avian dinosaurs, which evolved from saurischian (lizard-hipped) dinosaurs.
  27. The Heterodontosauridae evolved a tibiotarsus which is also found in modern birds. These groups aren't closely related.
  28. Ankylosaurs and glyptodont mammals both had spiked tails.
  29. Horned snouts independently is on non-related dinosaurs like ceratopsians and Triceratops, also rhinos and the brontotheres of the Cenozoic.
  30. Billed snouts on the duck-billed dinosaurs hadrosaurs strikingly convergent with ducks and duck-billed platypus.
  31. Ichthyosaurs a marine reptile of the Mesozoic era looked strikingly like dolphins.
  32. Beaks are independent in ceratopsian dinosaurs like Triceratops, birds and marine mollusks like squid and octopus.
  33. The Pelycosauria and the Ctenosauriscidae beared striking resemblance to each other because they both had a sail-like fin on their back. The Pelycosaurs are more closely related to mammals while the Ctenosauriscids are closely related to pterosaurs and dinosaurs.
    [edit] Other reptiles
  34. The thorny devil (Moloch horridus) is similar in diet and activity patterns to the Texas horned lizard (Phrynosoma cornutum), although the two are not particularly closely related.
  35. Modern Crocodilians resemble prehistoric phytosaurs, champsosaurs, certain labyrinthodont amphibians, and perhaps even the early whale Ambulocetus. The resemblance between the crocodilians and phytosaurs in particular is quite striking; even to the point of having evolved the graduation between narrow- and broad-snouted forms, due to differences in diet between particular species in both groups.
  36. The body shape of the prehistoric fish-like reptile Ophthalmosaurus is similar to those of other ichthyosaurians, dolphins (aquatic mammals), and tuna (scombrid fish).
  37. Death Adders strongly resemble true vipers, but are elapids.
  38. The Glass Snake is actually a lizard but is mistaken as a snake .
  39. Large Tegu lizards of South America have converged in form and ecology with monitor lizards, which are not present in the Americas.
  40. legless lizard-Pygopodidae are snake like lizard are much like true snakes.
  41. Mosasaurs of the Mesozoic era are like whales but are closely related to living monitor lizards and the Komodo Dragon.
  42. Anolis lizards are one of the best examples of both adaptive radiation and convergent evolution.
  43. Tuataras resemble lizards but in fact are in an order of their own, the Rhynchocephalia. The Tuatara has the sockets behind the eyes and has jagged extensions of the jaws instead of teeth.
    [edit] Avian
  44. The Little Auk of the north Atlantic (Charadriiformes) and the diving-petrels of the southern oceans (Procellariiformes) are remarkably similar in appearance and habits.
  45. Penguins in the Southern Hemisphere evolved similarly to flightless wing-propelled diving auks in the Northern Hemisphere: the Atlantic Great Auk and the Pacific mancallines.
  46. Vultures are a result of convergent evolution: both Old World vultures and New World vultures eat carrion, but Old World vultures are in the eagle and hawk family (Accipitridae) and use mainly eyesight for discovering food; the New World vultures are of obscure ancestry, and some use the sense of smell as well as sight in hunting. Birds of both families are very big, search for food by soaring, circle over sighted carrion, flock in trees, and have unfeathered heads and necks.
    Nubian Vulture, an Old World vulture
    Turkey Vulture, a New World vulture
    Hummingbird, a New World bird, with a sunbird, an Old World bird
  47. Hummingbirds resemble sunbirds. The former live in the Americas and belong to an order or superorder including the swifts, while the latter live in Africa and Asia and are a family in the order Passeriformes.
  48. In an odd cross-species example, an insect, the Hummingbird Hawk-moth (Macroglossum stellatarum), also feeds by hovering in front of flowers and drinking their nectar in the same way as the above mentioned birds.
  49. Certain longclaws (Macronyx) and meadowlarks (Sturnella) have essentially the same striking plumage pattern. The former inhabit Africa and the latter the Americas, and they belong to different lineages of Passerida. While they are ecologically quite similar, no satisfying explanation exists for the convergent plumage; it is best explained by sheer chance.
  50. Resemblances between swifts and swallows is due to convergent evolution.
  51. Downy Woodpecker and Hairy Woodpecker look almost the same, as do some Chrysocolaptes and Dinopium flamebacks, the Smoky-brown Woodpecker and some Veniliornis species, and other Veniliornis species and certain "Picoides" and Piculus. In neither case are the similar species particularly close relatives.
  52. Many birds of Australia, like wrens and robins, look like northern hemisphere birds but are not related.
  53. Oilbird like microbats and toothed whales developed sonar-like echolocation systems used for locating prey.
  54. The brain structure, forebrain, of hummingbirds, songbirds, and parrots responsible for vocal learning (not by instinct) is very similar. These types of birds are not related.
    [edit] Fish
  55. Goby dorsal finned like the lumpsuckers, yet they are not related.
  56. Sandlance fish and chameleons have independent eye movements and focusing by use of the cornea.
  57. Cichlids of South America and the "sunfish" of North America are strikingly similar in morphology, ecology and behavior.
  58. The Peacock Bass and Largemouth Bass are excellent examples.
  59. The Antifreeze protein of fish in the arctic and Antarctic, came about independently.
  60. Eel form are independent in the North American brook lamprey, neotropical eels, and the African spiny eel.
  61. Stickleback fish, there is widespread convergent evolution in Sticklebacks.
    [edit] Amphibians
  62. Plethodontid salamanders and Chameleons have evolved a harpoon-like tongue to catch insects.
  63. Two lineages of frogs among the Neobatrachia are due for convergent evolution.
  64. The Neotropical poison dart frog and the Mantella of Madagascar have independently developed similar mechanisms for obtaining alkaloids from a diet of mites and storing the toxic chemicals in skin glands. They have also independently evolved similar bright skin colors that warn predators of their toxicity (by the opposite of crypsis, namely aposematism).
  65. Caecilian are Lissamphibians that secondarly lost their limbs, resembling snakes
    [edit] Arthropods
  66. Assassin spiders comprise two lineages that evolved independently. They have very long necks and fangs proportionately larger than those of any other spider, and they hunt other spiders by snagging them from a distance.
  67. The smelling organs of the terrestrial coconut crab are similar to those of insects.
  68. Silk: Spiders, silk moths, larval caddis flies, and the weaver ant all produce silken threads.
  69. The praying mantis body type — raptorial forelimb, prehensile neck, and extraordinary snatching speed - has evolved not only in mantid insects but also independently in neuropteran insects Mantispidae.
  70. Agriculture some kinds of ants, termites, and ambrosia beetles have for a long time cultivated and tend fungi for food. These insects sow, fertilize, and weed their crops. A damselfish also takes care of red algae carpets on its piece of reef; the damselfish actively weeds out invading species of algae by nipping out the newcomer.
    [edit] Molluscs
  71. Bivalves and the gastropods in the family Juliidae have very similar shells.
  72. There are limpet-like forms in several lines of gastropods: "true" limpets, pulmonate siphonariid limpets and several lineages of pulmonate freshwater limpets.
  73. Cuttlefish show similarities between cephalopod (nautili, octopods and squid) and vertebrate (Mammalia...) eyes.
  74. Swim bladders — Buoyant bladders independently evolved in fishes, female octopus and siphonophores such as the Portuguese Man o' War.
  75. The phylum Mollusca members such as bivalves, and Phylum brachiopoda members, the brachiopods aka lampshells, independently evolved paired hinged shells for protection. The anatomy of their soft body parts is so dissimilar, however, that they are classified in separate, independent phyla. Biologists think that clams are more closely related to earthworms than they are to brachiopods.
  76. Jet propulsion in squids and in scallops: these two groups of mollusks have very different ways of squeezing water through their bodies in order to power rapid movement through a fluid. (Dragonfly larvae in the aquatic stage also use an anal jet to propel them, and Jellyfish have used jet propulsion for a very long time.)
    [edit] Other
  77. The notochords in chordates are like the stomochords in hemichordates.
  78. Elvis taxon in the fossil record developed a similar morphology through convergent evolution.
  79. Venomous sting: To inject poison with a hypodermic needle, a sharppointed tube, has shown up independently 10+ times: jellyfish, spiders, scorpions, centipedes, various insects, cone shell, snakes, stingrays, stonefish, the male duckbill platypus, and stinging nettles plant.
  80. Bioluminescence: A symbiotic partnerships with light-emitting bacteria developed many times independently in deep-sea fish, jellyfish, and in fireflies and glow worms.
  81. Parthenogenesis: Some lizards and insects have independent the capacity for females to produce live young from unfertilized eggs. Some species are entirely female.
    [edit] In plants
  82. Leaves have evolved multiple times - see Evolutionary history of plants.
  83. Prickles, thorns and spines are all modified plant tissues that have evolved to prevent or limit herbivory, these structures have evolved independently a number of times.
  84. Hallucinogenic toxins: Plants as diverse as the peyote cactus and the ayahuasca vine produce the same form of chemical toxin to deter predators.
  85. Stimulant toxins: Plants which are only distantly related to each other, such as coffee and tea, produce caffeine to deter predators.
  86. The aerial rootlets found in ivy (Hedera) are similar to those of the climbing hydrangea (Hydrangea petiolaris) and some other vines. These rootlets are not derived from a common ancestor but have the same function of clinging to whatever support is available.
  87. Flowering plants (Delphinium, Aerangis, Tropaeolum and others) from different regions form tube-like spur which contains nectar (that's why insect from one place sometimes can feed on plant from other which has such structure like the flower which is the traditional source of food for the animal).
  88. Both some dicots (Anemone) and monocots (Trillium) in inhospitable environments are able to form underground organs such as corms, bulbs and rhizomes for reserving of nutrition and water till the conditions become better.
  89. Insectivorous plants: Nitrogen-deficient plants have in at least 7 distinct times become insectivorous, like: flypaper traps\sundew, spring traps-Venus fly trap, and pitcher traps in order to capture and digest insects to obtain scarce nitrogen.
  90. Similar-looking rosette succulents have arisen separately among plants in the families Asphodelaceae (formerly Liliaceae) and Crassulaceae.
  91. The Orchids, the Birthwort family and Stylidiaceae have evolved independently the specific organ known as gynostemium, more popular as column.
  92. The Euphorbia of deserts in Africa and southern Asia, and the Cactaceae of the New World deserts have similar modifications (see picture below for one of many possible examples).
  93. Sunflower: some types of Sunflower and Pericallis are due to convergent evolution.
    Euphorbia obesa
    Astrophytum asterias
    [edit] Enzymes and biochemical pathways
  94. The existence of distinct families of carbonic anhydrase is believed to illustrate convergent evolution.
  95. The use of (Z)-7-dodecen-1-yl acetate as a sex pheromone by the Asian elephant (Elephas maximus) and by more than 100 species of Lepidoptera.
  96. The independent development of the catalytic triad in serine proteases independently with subtilisin in prokaryotes and the chymotrypsin clan in eukaryotes.
  97. The repeated independent evolution of nylonase in two different strains of Flavobacterium and one strain of Pseudomonas.
  98. The biosynthesis of plant hormones such as gibberellin and abscisic acid by different biochemical pathways in plants and fungi.[2][3]
  99. ABAC is a database of convergently evolved protein interaction interfaces. Examples comprise fibronectin/long chain cytokines, NEF/SH2, cyclophilin/capsid proteins. Details are described here.
  100. The independent development of three distinct hydrogenases exemplifies convergent evolution.

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This message is a reply to:
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Replies to this message:
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Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 22 of 107 (564327)
06-09-2010 9:30 PM
Reply to: Message 18 by BobTHJ
06-09-2010 6:31 PM


What is the ID Explanation?
BobTHJ writes:
Not all traits fit neatly into a nested hierarchy.
It isn't traits that one places into a nested hierarchy but organisms, and organisms have many traits that must be considered collectively. Pretty much everyone is aware that lone traits can not be used to classify organisms. What sense would it make to classify dolphins and bats together on the basis of one gene and ignore the other tens of thousands of genes that not don't match and the many genes that don't even exist in both species. Under no circumstances would anyone ever group dolphins and bats together, not based on phenotypic evidence, and not based on genetic evidence.
The specific collection of traits of many organisms are sufficiently distinct that they can be classified with a high degree of confidence, but for other organisms classification can often be difficult, and then we must fall back on genetic analysis which is much more clear and much less ambiguous. With an extremely high level of confidence genetic analysis tells us the degree of relatedness of organisms and where they belong within the nested hierarchy. There can be no doubt that organisms fit within a nested hierarchy.
It is only because it is unusual that the Prestin gene has come to the attention of creationists. It represents a case of convergent evolution that shaped not only a protein in two different organisms to become more similar, but also the common gene that produces it. But as I told you in the other thread, and as WK has told you in this one, when you look at the DNA you see that the mutations don't match.
The nested hierarchy is just a natural result of imperfect reproduction for generation after generation, and natural selection is what drives organisms toward similar solutions for better reproductive success given similar environments. It accounts for organisms converging on similar solutions, like arctic rabbits and polar bears converging on the solution of white fur and heavier coats.
How does ID account for what we see genetically in cases of convergent evolution, where the phenotypic similarity is belied by a completely different genetic underpinning?
--Percy

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 23 of 107 (564349)
06-10-2010 4:13 AM
Reply to: Message 18 by BobTHJ
06-09-2010 6:31 PM


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.
Why did Carl Linnaeus, who died 80 years before Darwin published the Origin of Species and believed that all life existed in immutable forms laid down by God, place all animal life into a nested hierarchy then? Why does that system, laid down 250 years ago, broadly persist to this day? Why haven't the tens of thousands of taxonomists working since that time noticed that this nested hierarchy doesn't match reality as you assert?
The answer, of course, is that as a matter of fact life does form nested hierarchies. And the hierarchies it forms look very similar whether you look at genetics, morphology or fossil data.

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Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 24 of 107 (564352)
06-10-2010 5:12 AM
Reply to: Message 18 by BobTHJ
06-09-2010 6:31 PM


Were I a darwinist attempting to assemble a phylogenetic tree then I agree with this assessment.
Taxonomic trees predate Darwin.
However, as I mentioned in my previous post, where do you draw the line? Not all traits fit neatly into a nested hierarchy.
True. For example, I have blue eyes and so does a Siamese cat. This suggests that I am a member of the "cat kind", and so falsifies baraminology ... oh, wait ... you didn't want that to be false, did you?
The overall evidence for a nested hierarchy is not high
Yes it is. That's kinda why biologists, who, unlike you, know about biology, are so certain of their conclusion. This is, as Mr Jack points out, the reason why biologists have classified organisms in a nested hierarchy since the eighteenth century, before evolution was even thought of.
- the many cases of 'convergent evolution' demonstrate this.
You know, repeating a failed argument doesn't make it more convincing.
What does have a lot of evidence is the conclusion that creatures with similar morphological features will share similar genes.
To be more precise, there is a lot of evidence that creatures with recent common ancestors will share similar genes whether they are morphologically similar or not, and that creatures with superficially similar morphology but more distant common ancestry (for example the wolf and the marsupial wolf) will be more genetically dissimilar.
This does nothing to prove or disprove common ancestry ...
Yes it does --- it is a prediction of the theory. And it's true. You know, like all the other predictions of the theory.
Edited by Dr Adequate, : No reason given.
Edited by Dr Adequate, : No reason given.

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Peepul
Member (Idle past 5018 days)
Posts: 206
Joined: 03-13-2009


Message 25 of 107 (564363)
06-10-2010 6:23 AM
Reply to: Message 18 by BobTHJ
06-09-2010 6:31 PM


quote:
The overall evidence for a nested hierarchy is not high - the many cases of 'convergent evolution' demonstrate this
Hi Bob,
The nested hierarchy is evidenced by many things - genetics, morphology, the fossil record. Taking organisms as a whole, rather than just focussing on convergent features, it emerges clearly from the data. Recent genetic evidence (ERVs, retrotransposons, pseudogenes) has only made the case stronger.
Convergent evolution is expected to occur. The question is - how much convergence would be a threat to the evolutionary view?
My view is in line with WK - only genetic convergence is a potential threat to this view. And it only becomes a threat if the probability of these genetic convergences, taken as a whole, is very low, with the additional proviso that there is no natural mechanism of horizontal gene transfer to account for these convergences.
So, how much convergence would be expected to occur under the evolutionary scenario? How much convergence is there? How unlikely is that to have occurred by chance? iIf there is an excess, what leads you to think there is no natural mechanism out there to account for it?
If you can answer these questions, you will be on your way to building a case.

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Taq
Member
Posts: 9973
Joined: 03-06-2009
Member Rating: 5.7


(1)
Message 26 of 107 (564414)
06-10-2010 11:14 AM
Reply to: Message 18 by BobTHJ
06-09-2010 6:31 PM


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.
You look for the signal that sticks out above the noise. When you listen to the radio do you tap your foot to the beat of the music or the popping of the static?
Phylogenetic trees will always have noise. It is expected. However, if creationism is true then there is no reason that we should observe a phylogenetic signal at all, but we do. We observe a very strong one. As others have mentioned, it was creationists like Linnaeus who constructed the first phylogenies based on shared characteristics.
The overall evidence for a nested hierarchy is not high - the many cases of 'convergent evolution' demonstrate this.
And again, we are looking at superficial resemblance. One of the better examples is the duck and the platypus. From the outside their bills do resemble one another. However, when you examine the underlying skeletal structure they are not alike at all. The platypus has a mammalian jaw complete with a single lower dentary bone and even cusped cheek teeth. The duck has a very standard bird jaw with multiple lower jaw bones and no cusped teeth. If you want to argue that a designer is reusing designs then why do we see a similar structure derived from such different sources?

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Asking
Junior Member (Idle past 5038 days)
Posts: 19
Joined: 05-19-2010


Message 27 of 107 (564420)
06-10-2010 11:55 AM
Reply to: Message 26 by Taq
06-10-2010 11:14 AM


Incidently there are several good examples of convergent evolution between mammals and marsupials. This site gives examples of them (http://txtwriter.com/Backgrounders/Evolution/EVpage14.html). This is evidence for evolution, not evidence against it.

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BobTHJ
Member (Idle past 4998 days)
Posts: 119
Joined: 06-02-2010


Message 28 of 107 (564628)
06-11-2010 12:30 PM
Reply to: Message 10 by Taq
06-07-2010 2:00 PM


quote:
If separate creation were true then the exceptions should be the rule. They aren't. What we see with the prestin gene in bats and toothed cetaceans is 10-14 common derived amino acid substitutions out of hundreds. Given the importance of the prestin gene in audition (knock out mice have a >100-fold decrease in hearing, source), it is not too surprising that amino acid substitions are highly constrained and would be strongly selected for
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:
False. They share 10-14 of the same derived amino acid substitions. You can go to NCBI and search for the genes themselves. A search for "prestin bat" or "presting dolphin" will give you the results you need. You will find that the genes are not identical. In fact, there are fewer differences between dolphins than there are between dolphins and bats. They are far from identical. It's a bit tough to show these comparisons on internet forums, but if you want I can try to figure something out (or someone else with better http skills can give it a try).
Thanks for the NCBI link....I didn't realize that stuff was available online for free
quote:
Are you saying that if two species share a common ancestor that they would NOT share common genes?
No....common ancestry would imply a close genetic makeup.

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Taq
Member
Posts: 9973
Joined: 03-06-2009
Member Rating: 5.7


Message 29 of 107 (564631)
06-11-2010 12:48 PM
Reply to: Message 28 by BobTHJ
06-11-2010 12:30 PM


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.
Why is that a problem?
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?
Because their survival is not as dependent on their sense of hearing. Do you wonder why humans don't have a blowhole on top of their head since it is vital to dolphins?
I have a hard time picturing a situation where hearing higher frequency sound wouldn't be an increase in fitness.
Are wolves able to take down elk without echolocation?

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Huntard
Member (Idle past 2295 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 30 of 107 (564647)
06-11-2010 2:24 PM
Reply to: Message 27 by Asking
06-10-2010 11:55 AM


Asking writes:
Incidently there are several good examples of convergent evolution between mammals and marsupials.
Marsupials are mamals.

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