exaptations (Introduction)
by David Turell 
, Monday, July 15, 2013, 15:09 (4150 days ago)
More common than adaptation:-"If exaptations are pervasive, then natural selection—which few doubt is critical for the preservation and spreading of traits—may not be that important for the origin of innovations in life's history."-If exaptations are that common, it is another major blow to Darwinian theory.- http://www.the-scientist.com//?articles.view/articleNo/36508/title/Q---A--Evolution-Makes-Do/-Another example of pre-planning?
exaptations
DAVID: More common than adaptation:-http://www.the-scientist.com//?articles.view/articleNo/36508/title/Q---A--Evolution-Mak...-"If exaptations are pervasive, then natural selection—which few doubt is critical for the preservation and spreading of traits—may not be that important for the origin of innovations in life's history."-May I suggest that natural selection has no importance whatsoever for the origins of innovations in life's history. Darwin believed that innovations were caused by random mutations, whereas natural selection was the process which decided which innovations would survive and which would not. Not even Nature can select from organs that do not yet exist. DAVID: If exaptations are that common, it is another major blow to Darwinian theory.-Not according to the article you have quoted!-The Scientist: Where did the notion of exaptations come from? Andreas Wagner: Stephen Jay Gould first coined the term to describe traits that may be simple by-products of other traits. Also, Darwin said in his Origin of the Species back in 1859 that organs that serve a particular purpose may have originated for a completely different purpose. So even Darwin was aware that exaptations exist, although they didn't have that word at the time.-It's coming to something when Darwin's theory comes under fire because he didn't invent the word "exaptation" to cover a process he was aware of! According to AW "This opens a huge can of worms for evolutionary biologists because it becomes very hard to distinguish adaptation from exaptation." If it's so hard to distinguish, how can the researchers claim that exaptation is more common than adaptation? No doubt Darwin realized the same problem: you'd need a complete, consecutive fossil record of every organ to know what was adapted and what was new. And frankly, how much does it matter? The borderline between adaptation and innovation is bound to be blurred, and exaptation simply describes the grey area. -It stands to reason that if there is an intelligent mechanism at work within the genome (and there has to be, even though we can't account for it), and if an innovation survives because it is beneficial, its purpose could be changed if the environment demanded or allowed for change. The only other way the process could possibly work would be if you believed in a god who intervened in order to create every single innovation and adaptation! A totally unnecessary complication even for a theist. DAVID: Another example of pre-planning?-No, another example of the intelligent genome at work.
exaptations
by David Turell , Tuesday, July 16, 2013, 16:15 (4149 days ago) @ dhw
> DAVID: If exaptations are that common, it is another major blow to Darwinian theory. > > dhw: Not according to the article you have quoted! > "And frankly, how much does it matter? The borderline between adaptation and innovation is bound to be blurred, and exaptation simply describes the grey area." > > dhw: It stands to reason that if there is an intelligent mechanism at work within the genome (and there has to be, even though we can't account for it), and if an innovation survives because it is beneficial, its purpose could be changed if the environment demanded or allowed for change. The only other way the process could possibly work would be if you believed in a god who intervened in order to create every single innovation and adaptation! A totally unnecessary complication even for a theist.-Not an unnecessary complication. Lets use Tattersall's favorite exaptation, the adaptations for speech. The lowering of the larynx requiring the development of the epiglottis as a trap door to prevent choking, reshaping of the pharynx, and development of special tongue muscles and attachments all began 500,000 years BEFORE Homo erectus. H. Erectus probably had some rudimentary speech. Why did evolution create a disadventageous larynx, when no need existed at the time. An 'intelligent genome' with foresight? That would be a stretch even for you.
exaptations
by David Turell , Tuesday, July 16, 2013, 18:37 (4148 days ago) @ David Turell
Try this approach to exaptations. They really smell of teleology:--http://www.sciencedaily.com/releases/2013/07/130715134424.htm-"The findings underscore the idea that traits we see now -- even complex ones, like color vision -- may have had neutral origins that sat latent for generations before spreading through populations, Wagner says."-Why keep something that is useless and 'latent' for generations. Why doesn't it disappear? Does natural selection really have any true selective capacity for parts that are just sitting around?-"From a strictly scientific perspective, the exaptation explanation does not work. For it requires that evolution is constantly getting lucky as it constructs all kinds of biological subcomponents and machines which, as luck would have it, just happen to fit together to form completely new and different machines which work wonders."-http://darwins-god.blogspot.com/2013/07/this-new-paper-on-how-innovations.html
exaptations: thru biochemistry
by David Turell , Tuesday, July 16, 2013, 19:35 (4148 days ago) @ David Turell
Another approach to complexity without natural selection;-"Thornton and his colleagues have uncovered precisely the kind of evolutionary episode predicted by the zero-force evolutionary law. Over time, life produced more parts—that is, more ring proteins. And then those extra parts began to diverge from one another. The fungi ended up with a more complex structure than their ancestors had. But it did not happen the way Darwin had imagined, with natural selection favoring a series of intermediate forms. Instead the fungal ring degenerated its way into complexity."-http://www.scientificamerican.com/article.cfm?id=the-surprising-origins-of-evolutionary-complexity&page=5-A very thorough and complete disucussion of alternate pathways to complexity.-"Gray, McShea and Brandon acknowledge the important role of natural selection in the rise of the complexity that surrounds us, from the biochemistry that builds a feather to the photosynthetic factories inside the leaves of trees. Yet they hope their research will coax other biologists to think beyond natural selection and to see the possibility that random mutation can fuel the evolution of complexity on its own. "We don't dismiss adaptation at all as part of that," Gray says. "We just don't think it explains everything.'"
exaptations
Dhw: It stands to reason that if there is an intelligent mechanism at work within the genome (and there has to be, even though we can't account for it), and if an innovation survives because it is beneficial, its purpose could be changed if the environment demanded or allowed for change. The only other way the process could possibly work would be if you believed in a god who intervened in order to create every single innovation and adaptation! A totally unnecessary complication even for a theist. -DAVID: Not an unnecessary complication.-So are you saying that God "intervened in order to create every single innovation and adaptation"? How do you think he did it? Did he grab hold of each individual creature and psychokinetically adjust the genome every time he wanted to make a change? I know you can't answer. It's a mystery you're happy to live with. But see the next problem. Your various posts ask the question: "Why keep something that is useless and 'latent' for generations. Why doesn't it disappear?" And "Why did evolution create a disadvantageous larynx, when no need existed at the time?" Until very recently everyone thought "junk DNA" was just that, but now scientists are not so sure. Do you honestly think we KNOW how things worked hundreds of thousands of years ago? Every new find produces new theories. Perhaps you're thinking this will sound like pre-planning. But if, as you have repeatedly told us, God intervenes, why bother with a disadvantageous larynx 500,000 years before he needs it? He could just step in again and dabble. The mixture of laissez-faire and direct intervention constantly leads you to more and more "unnecessary complications". Gray & Co "hope their research will coax other biologists to think beyond natural selection and to see the possibility that random mutations can fuel the evolution of complexity on its own. "We don't dismiss adaptation at all as part of that," Gray says. "We just don't think it explains everything."-I don't think natural selection and adaptation explain everything either. And I doubt whether random mutations explain anything at all. David, you have provided us with masses of examples that describe the intelligent processes underlying all the organs we know today. Science has shown that cells, microorganisms, plants, our fellow animals communicate, take decisions, cooperate, form communities. There is nothing random in this. No-one has the slightest difficulty understanding that humans adapt and innovate by using their intelligence. So why is it so difficult to imagine that other forms of life have done the same, going right back to the earliest of those forms?
exaptations
by David Turell , Friday, September 06, 2013, 18:46 (4096 days ago) @ dhw
A new study using metabolic networks to sort out adaptation from exaptation. The article is somewhat confusing because whole organ exaptations are not mentioned. Main example, our larynx dropped in postion 500,000 years before speech started, and created all sorts of choking problems in the process, counter to the idea that natural selection allows only the fittest stuff.-http://www.scientificamerican.com/article.cfm?id=evolution-as-opportunist&page=2
exaptations; dinosaur to bird?
by David Turell , Wednesday, April 29, 2015, 18:57 (3496 days ago) @ David Turell
Could the new tiny dinosaur with an extra bone be an exaptation on the way to birds?-http://www.nature.com/news/more-on-unicorns-1.17419?WT.ec_id=NATURE-20150430-"Except that Yi qi is different. Attached to each wrist is a strut, made of bone or calcified cartilage, which cannot simply be homologized with regular wrist or hand bones. The strut seems to be a new structure made from an accessory wrist bone, possibly a sesamoid — the kind of bone usually embedded in a tendon or muscle. The ‘thumb' of the giant panda is made of just such a bone. The sesamoid of Yi qi (if that's what it is) is much larger, however, in relation to the animal as a whole — equal in length to the bones of the forearm. It had to be there for a reason, but what was it?-"It is here that we enter unicorn territory — for no dinosaur, however unusual, has been found with anything like this feature. The authors are appropriately cautious, therefore, in their interpretation. They point to the hint of a suggestion that some soft tissue, preserved alongside these curious elements, represents what might have been a membrane that the sesamoid bone supported. From that, they suggest that Yi qi had membranous wings and might have glided from branch to branch, in much the same way as various tree-living mammals and reptiles do today. But it was probably not capable of powered flight as birds and bats are — and as were, presumably, the extinct pterosaurs, which were (one must stress) only distant relatives of dinosaurs and birds."