Another Revolution in our Knowledge of Evolution
Until recently, evolutionary hypotheses envisioned their [feathers] origin through elongation of broad, flat scales driven by selection for aerial locomotion such as gliding or flapping flight. Over the course of the past two decades, fossil discoveries, especially from northeast China, have revealed that the early precursors of feathers were filament-like rather than expanded scales and that branched pinnate feathers of modern aspect predate the origin of active flight. The revolution in our understanding of feather evolution continues, driven by rapid fossil discoveries and by new information from the study of extant birds.
So in other words, feathers evolved, and as luck would have it they were a great solution for flight. So with feathers already available, flying later evolved. Evolution got lucky again. And here all along we thought feathers evolved so creatures could fly.
It’s another giant leap forward in our knowledge of how the world came to be. It is literally a revolution in our knowledge of evolution. But how, on the one hand, can our knowledge be so flawed while, on the other hand, we can know for certain that evolution is a fact?
Tsk. tsk. CH is still having trouble with the concepts of 'hypothesis', 'theory', and 'fact' I see.
ReplyDeleteProbably why he's so continually confused over the evolutionary sciences.
The most surprising thing about Darwinian evolution is the stupendous level of stupidity it requires from its believers. How do they get away with teaching this crap?
ReplyDeleteIn what way is this new?
ReplyDeleteFossil evidence suggesting that feathers may have evolved originally for some function other than flight has been around for some time. So has speculation about possibilities such as a genetic mutation that caused what would have been scales to develop as "bristles" or rudimentary feathers.
For anyone interested, this National Geographic article from 2011 has a useful summary. Perhaps BA77 would like to add it to his archive if he doesn't already have it.
But how, on the one hand, can our knowledge be so flawed while, on the other hand, we can know for certain that evolution is a fact?
ReplyDeleteHas anyone ever claimed that our knowledge is complete and perfect? Ask any scientist - certainly biologists (physicists are a different matter) - and they will be happy to affirm that our knowledge is incomplete.
The fact that our knowledge is incomplete is not the same as saying we have no knowledge at all, however. What we do have is sufficient to support the claim that the process of evolution is scientific fact by Gould's definition.
Flight: The Genius of Birds - Official Trailer
ReplyDeletehttp://www.youtube.com/watch?v=46rE4BfWN_M
Ian: What we do have is sufficient to support the claim that the process of evolution is scientific fact by Gould's definition.
ReplyDeleteJeff: People believed that much before we ever knew about DNA, etc. The idea that traits are inherited goes WAY back. Explaining it in terms of recombination, etc doesn't add an iota of support to the hypothesis of naturalistic UCA.
"And here all along we thought feathers evolved so creatures could fly."
ReplyDeleteIf by "we" you mean "people who don't understand evolutionary theory", then, yeah, sure. Or possibly "people who are still into Lamarckianism". Otherwise, no. But you know that already, don't you Cornelius?
If your "evolution instructor informed you that feathers evolved so creatures could fly" then perhaps it is not so surprising that you aren't terribly impressed with the theory of evolution, Cornelius.
ReplyDeleteIt doesn't even make any sense.
If your evolution instructor had said that flying creatures evolved feathers because flight feathers made flight more efficient, that would have made some sense.
However, as the very article you cite says, the last two decades of research into the evolution of feathers have revealed that feathers evolved before flight. Which makes much better sense, given that birds do not have wing membranes like bats or pterosaurs, and therefore are unlikely to have had flying featherless ancestors - much more likely to have had non-flying feathered ancestors.
Which is what we have known to be the case for a couple of decades!
Your "news" is "olds", Cornelius, not for the first time!
So once upon a time it happens that a scale started to change and became a protofeather in an animal that found it usefull for we do not know what. And it happened to be that this animal started to try to fly. And as this animal started to fly protofeathers started to change to feathers and then we got birds and we lived happilly ever after. Specially because it didn´t happened again never after. None of the animals that jump from tree to tree never had the lucky to develop a proto feather like organ, so birds are the unique that can fly.
DeleteBlas
DeleteNone of the animals that jump from tree to tree never had the lucky to develop a proto feather like organ, so birds are the unique that can fly.
So we don't have any flying bats, flying insects, or sugar gliders. We never had any flying pterosaurs. Only birds can fly.
This public service announcement brought to you by the Creationist Coalition for Ignorance in Science.
Cornelius Hunter: As a new paper explains:
ReplyDeleteHeh. A new paper filed under "PERSPECTIVE".
OK, this post got me reading about birds, feathers, flight...I usually don't care about evolution per se but something shocked me when I read on evolution of bird flight.
ReplyDeleteBird flight ,(source Wikipedia) evolved because birds were jumping of trees or running uphill or something like that. :O
I don't know how seriously these people view themselves. They remind me of commander Hadfield's singing on ISS, is this serious or a joke?
Eugen
DeleteBird flight ,(source Wikipedia) evolved because birds were jumping of trees or running uphill or something like that. :O
Those are indeed two main competing hypotheses of the origin of bird flight, tree-down and ground-up. "Ambush" jumping / gliding from branches to catch prey, and wing-assisted running where the forelimbs evolved to allow long gliding jumps when sprinting across ground. Each method has some supporting evidence, and each behavior can be seen in extant animals today. Of course it's possible that both are correct and that different avian lineages followed different pathways to the air.
Right now the ground-up hypothesis seems to have more support
Assessing Arboreal Adaptations of Bird Antecedents: Testing the Ecological Setting of the Origin of the Avian Flight Stroke
"Abstract: The origin of avian flight is a classic macroevolutionary transition with research spanning over a century. Two competing models explaining this locomotory transition have been discussed for decades: ground up versus trees down. Although it is impossible to directly test either of these theories, it is possible to test one of the requirements for the trees-down model, that of an arboreal paravian. We test for arboreality in non-avian theropods and early birds with comparisons to extant avian, mammalian, and reptilian scansors and climbers using a comprehensive set of morphological characters. Non-avian theropods, including the small, feathered deinonychosaurs, and Archaeopteryx, consistently and significantly cluster with fully terrestrial extant mammals and ground-based birds, such as ratites. Basal birds, more advanced than Archaeopteryx, cluster with extant perching ground-foraging birds. Evolutionary trends immediately prior to the origin of birds indicate skeletal adaptations opposite that expected for arboreal climbers. Results reject an arboreal capacity for the avian stem lineage, thus lending no support for the trees-down model. Support for a fully terrestrial ecology and origin of the avian flight stroke has broad implications for the origin of powered flight for this clade. A terrestrial origin for the avian flight stroke challenges the need for an intermediate gliding phase, presents the best resolved series of the evolution of vertebrate powered flight, and may differ fundamentally from the origin of bat and pterosaur flight, whose antecedents have been postulated to have been arboreal and gliding."
Why do you think either hypothesis is not serious?
Thorton, I honestly expected something more - I don't know - complicated. I don't usually read about animal evolution topic but I'll read article you linked, thanks. I have a policy: if you link it - we'll read it.
ReplyDeleteThing that doesn't help at all: my daughter has a lot of plush animals, some are birds with short fuzzy wings. After reading Wikipedia I imagined a bird with short, fat feathery wings running and jumping, trying to take off. Ain't gonna happen Pingu!
(not very deep but I can't help it)
Eugen
DeleteThorton, I honestly expected something more - I don't know - complicated. I don't usually read about animal evolution topic but I'll read article you linked, thanks. I have a policy: if you link it - we'll read it.
There is a fair amount of research on WAIR - wing assisted incline running - in birds. Do a Google Scholar search to see the latest published results. Mechanical analysis shows having even small flightless wings move in a flapping motion while running reduces the energy expenditure and therefore would be a trait likely for selection.
The phylogeny of wing assisted incline running
There have even been small robots wings built to test the hypothesis
Incline running by wing-assisted robot
Thing that doesn't help at all: my daughter has a lot of plush animals, some are birds with short fuzzy wings. After reading Wikipedia I imagined a bird with short, fat feathery wings running and jumping, trying to take off. Ain't gonna happen Pingu!
Maybe not in that specific animal, but if each generation can run / glide a bit better than the last, eventually...
Turns out the partial flapping helps in getting down from high places too
Controlled flapping descent and the evolution of flight
I don't favor either hypothesis (tree-down or ground-up) over the other but the research is interesting. Again, it may be that both ideas are correct.
Eugen
ReplyDelete"(not very deep but I can't help it)"
Just common sense.
Blas
DeleteJust common sense.
Like common sense tells us the sun and moon revolve around a stationary Earth.
Creationist "common sense" science - all you can do is laugh.
Great videos,it seems wing motion helps climbing a lot. Overall it's like a ratchet action, claws hold onto the bark and wings help jump forward, claws hold etc. I'll check article within couple of days.
ReplyDeleteThorton, I read the article but I must report it was too technical for me. Biology study of a whole organism is in a way very complicated. Animals eat, fight, act on instincts, run, fly etc..so studying them can get confusing (for me).
ReplyDeleteA bird needs to outrun its predator in order to survive and reproduce. It would be desirable for bird to have bigger and stronger wings so it can climb a tree for a longer time and faster, too. With stronger, bigger wings, she'll mange to escape and avoid becoming dinner. The mini wing doesn't know how to become stronger and bigger.
Let’s zoom in to the left winglet, from the winglet level to the muscle tissue level, to groups of cells forming muscle fibers to two cells: cell A and cell B.
What happens to the cells forming a muscle fiber?
We know each cell can randomly mutate so any cell has a 50% chance for beneficial mutation and a 50% chance for detrimental mutation.
Cells A and B are next to each other, incorporated into the layer containing huge number of cells forming a muscle fiber. Cell A has a random mutation, which will benefit the strength of the layer. Cell B has a random mutation, which will be detrimental to the strength of the layer. Net effect equals zero.
This scenario is happening at the same time in every one of the billions of cells forming a bird’s winglet. If we look at any group of cells, in that group half of the cells will be working in a beneficial direction and the other half in a detrimental direction.
Cells have to locally coordinate somehow via chemical signaling to form an extra layer of muscle fibers i.e. increase size of the wing. Cells forming different tissues in the winglet must coordinate; this would be at the single organ level.
Bigger wing will need a bigger heart so there has to be coordination between organs, which means there has to be global coordination. All this cannot continue in a random way because symmetry of an organism has to be preserved…this is mind-boggling.
Eugen: Cells A and B are next to each other, incorporated into the layer containing huge number of cells forming a muscle fiber. Cell A has a random mutation, which will benefit the strength of the layer. Cell B has a random mutation, which will be detrimental to the strength of the layer. Net effect equals zero.
ReplyDeleteWhile cells certainly mutate during the life cycle of an organism, they are all descended from a single cell; in multicellular organisms, a zygote formed from two gametes. Inheritance is channeled through that single cell. If a mutation occurs in the gametes or the zygote, then every cell of the organism will inherit that mutation—including the gametes of the organism that develops from the zygote.
The difference may only have to be slight to confer an advantage.
--
Niels Bohr and Albert Einsten were taking a walk in the woods, vigorously debating the philosophical underpinnings of quantum theory, when a gigantic bear suddenly burst out of the underbrush and raced toward them. Bohr immediately whipped out his fine running shoes and began lacing them up.
Einstein, furrowing his brow at Bohr, said: "Niels, there's no way you can outrun that bear."
"That's true, dear Albert," Bohr calmly replied, "but I don't need to outrun the bear. I only need to outrun you."
Eugen
ReplyDeleteWe know each cell can randomly mutate so any cell has a 50% chance for beneficial mutation and a 50% chance for detrimental mutation.
Er, no. As Zachriel already pointed out, a single mutation present in the DNA of a zygote will be passed to the DNA of all the cells. Each cell doesn't have to mutate individually.
Also, individual pieces of the winglet don't each need a separate mutation. It may be just a change to regulatory genes which affect the timing of development. Instead of an instruction "grow parts for a winglet for 20 hours" we get "grow parts for a winglet for 21 hours". That would result in slightly bigger, longer, stronger winglets. If those bigger winglets help the possessor survive they will be selected for and the "21 hour" variety passed to future generations.
A good example is the mutations to the Bmp2 gene which controls the digit length in bats. The mutation resulted in a greatly elongated fingers which effectively turned a mammal's paw into a wing.
Development of bat flight: Morphologic and molecular evolution of bat wing digits
Abstract: The earliest fossil bats resemble their modern counterparts in possessing greatly elongated digits to support the wing membrane, which is an anatomical hallmark of powered flight. To quantitatively confirm these similarities, we performed a morphometric analysis of wing bones from fossil and modern bats. We found that the lengths of the third, fourth, and fifth digits (the primary supportive elements of the wing) have remained constant relative to body size over the last 50 million years. This absence of transitional forms in the fossil record led us to look elsewhere to understand bat wing evolution. Investigating embryonic development, we found that the digits in bats (Carollia perspicillata) are initially similar in size to those of mice (Mus musculus) but that, subsequently, bat digits greatly lengthen. The developmental timing of the change in wing digit length points to a change in longitudinal cartilage growth, a process that depends on the relative proliferation and differentiation of chondrocytes. We found that bat forelimb digits exhibit relatively high rates of chondrocyte proliferation and differentiation. We show that bone morphogenetic protein 2 (Bmp2) can stimulate cartilage proliferation and differentiation and increase digit length in the bat embryonic forelimb. Also, we show that Bmp2 expression and Bmp signaling are increased in bat forelimb embryonic digits relative to mouse or bat hind limb digits. Together, our results suggest that an up-regulation of the Bmp pathway is one of the major factors in the developmental elongation of bat forelimb digits, and it is potentially a key mechanism in their evolutionary elongation as well.
Instead of thinking of DNA as a blueprint where every dimension must randomly change in unison, it may be be better to think of DNA as a recipe. The difference between "bake for 20 minutes" and "bake for 30 minutes" may be dramatic.
Just add Bmp2 and you make a flying bat from a mice! Is interesting that 50 millions years ago a mouse increased the exppresion of Bmp2 and became a bat suddenly, right the first time and never again. I wander why no mice increased his bmp2 expression the las 5 millions years.
DeleteBlas
DeleteJust add Bmp2 and you make a flying bat from a mice!
No, that's just one of many changes. But despite your Creationist ignorance you do seem to be learning. Last week you told us that birds were the only animals that ever developed flight.
Blas: Just add Bmp2 and you make a flying bat from a mice!
ReplyDeleteIt took other changes, of course.
Blas: Is interesting that 50 millions years ago a mouse increased the exppresion of Bmp2 and became a bat suddenly, right the first time and never again.
Not so suddenly. For instance, Onychonycteris finneyi lacked echolocation, and had shorter wings, longer legs and more claws, than modern bats.
Blas: I wander why no mice increased his bmp2 expression the las 5 millions years.
Because the niche is already filled by highly adapted modern bats.
Zachriel
Delete"It took other changes, of course."
And occurred simultaneously or sequentially?
"Not so suddenly. For instance, Onychonycteris finneyi lacked echolocation, and had shorter wings, longer legs and more claws, than modern bats."
The paper states:
" This absence of transitional forms in the fossil record led us to look elsewhere to understand bat wing evolution."
"Because the niche is already filled by highly adapted modern bats."
And actual mices knows that then do not even try.
Blas: And occurred simultaneously or sequentially?
ReplyDeleteThe fossil evidence indicates that flight came before echolocation.
Blas: The paper states: "This absence of transitional forms in the fossil record led us to look elsewhere to understand bat wing evolution."
Yes, molecular evidence can complement the fossil evidence.
Blas: And actual mices knows that then do not even try.
"Do or Do not. There is no try."
Zachriel
Delete"The fossil evidence indicates that flight came before echolocation."
As always you aswer other questions I said:
" Just add Bmp2 and you make a flying bat from a mice! "
"Yes, molecular evidence can complement the fossil evidence."
Again. The molecular evidence do not shows there are more steps than what fossil record shows.
"Do or Do not. There is no try."
So I´m right, add Bmp2 and you have a bat or not. Suddenly, right the first time.
Blas: As always you aswer other questions
ReplyDeleteYou specifically asked whether the changes "occurred simultaneously or sequentially". The fossil evidence indicates that flight came before echolocation.
Blas: The molecular evidence do not shows there are more steps than what fossil record shows.
The molecular evidence shows how the process could have occurred incrementally. Studies of bat embryos supports this, as well.
Blas: So I´m right, add Bmp2 and you have a bat or not. Suddenly, right the first time.
Bmp2 is found in other vertebrates. As we pointed out, an early bat had shorter arms and longer legs, just the sort of intermediate expected by evolutionary theory.
It should be pointed out that not all bats echolocate, about 30% of bat species lack the capability. Also, the species that do use echolocation don't all do it the same way.
DeleteWhy did the magic Designer forget to put echolocation in some bats, and why did he come up with different ways for the bats that do have it?
Evolution explains those issues quite nicely. ID/Creationism, not so much so.
Zachriel said
Delete"You specifically asked whether the changes "occurred simultaneously or sequentially". The fossil evidence indicates that flight came before echolocation."
Again missing deliberatly the point. A flying bat is a bat that just occurred by adding more Bmp2. Then if you want an echolocation just mutate ten aminoacids in prestin.
"The molecular evidence shows how the process could have occurred incrementally. Studies of bat embryos supports this, as well."
So you are still a supporte of the "biogenetic law" (http://en.wikipedia.org/wiki/Recapitulation_theory) that never was teached as a true law by evolutionists.
"Bmp2 is found in other vertebrates. As we pointed out, an early bat had shorter arms and longer legs, just the sort of intermediate expected by evolutionary theory."
The paper says that we do not have fossils of that bat with shorter arms and longer legs. Do you immagine it? Could be evolution the result of the immagination of darwinists?
Zachriel
ReplyDeletethanks for explanation and an excellent joke, I 'll use it in the future. Let me modify it a little.
Velikovsky and Eugen are walking by the forest and yapping about astronomy. Suddenly big bear runs from the forest and starts chasing them. They both get eaten because they are too fat, old and slow to run. They wish they had wings.
Thorton
"Each cell doesn't have to mutate individually"
OK but it may mutate.
"It may be just a change to regulatory genes"
Do you mean while organism is growing but once it's fully grown regulatory genes are less involved?
" If those bigger winglets help the possessor survive they will be selected for and the "21 hour" variety passed to future generations."
I guess it would be gene regulation for both winglets to preserve symmetry, bones must strengthen as well and number of blood vessels, nerves should increase. I would guess heart too, because more blood has to be pumped into bigger muscles...all at the same time? If yes then changes could be coming in groups- functional blocks.
I won't go too far because it's not my field but I would appreciate yours and Zachriel's opinion.
eugen
ReplyDeleteOK but it may mutate.
Yes but the only mutations that affect evolution and may be carried forward are those that occur in germline cells - gametes (sperm or egg), and the cells that produce them, all the way back to the zygote. Mutations in other cells (somatic cells) that make up the rest of the body don't get passed on.
Do you mean while organism is growing but once it's fully grown regulatory genes are less involved?
Any time after the zygote is formed, although mostly in the early stages of development before birth.
I guess it would be gene regulation for both winglets to preserve symmetry, bones must strengthen as well and number of blood vessels, nerves should increase. I would guess heart too, because more blood has to be pumped into bigger muscles...all at the same time? If yes then changes could be coming in groups- functional blocks.
Animals with bilateral symmetry have one set of genes that control development of both sides.
You're still thinking in terms of individual building blocks being assembled but that's not how it happens. All the parts - bones, muscle, blood vessels - develop simultaneously, in parallel, based on the DNA in the original zygote. When you make a change to one part (say digit length) you automatically affect all the other related parts as they develop together.
Think for a moment of the case where a 6' man has a child with a 5' woman, and the offspring grows to 5'6". Do you think the kid had to have millions of individual mutations in millions of cells to get his bones/muscles/blood vessels, etc. to the the right size? Or was the new genetic combination formed from the parent's DNA (with some dominant genes, some recessive genes) enough to do it?
Blas: A flying bat is a bat that just occurred by adding more Bmp2.
ReplyDeleteNo. There are many changes involved. This was pointed out to you before.
Blas: So you are still a supporte of the "biogenetic law" (http://en.wikipedia.org/wiki/Recapitulation_theory) that never was teached as a true law by evolutionists.
It's not recapitulation, but descent with modification. A bat doesn't go through a 'fish-stage', but shares a common ancestry with fish so they share many of the same embryonic characteristics, especially during early development.
Blas: The paper says that we do not have fossils of that bat with shorter arms and longer legs.
The paper on Onychonycteris was published after the paper you cited.
Sears et al., Development of bat flight: Morphologic and molecular evolution of bat wing digits, PNAS 2006.
Simmons et al., Primitive early Eocene bat from Wyoming and the evolution of flight and echolocation, Nature 2008.
It's amazing how the molecular data complements the paleontological data, and how the molecular data predicts what you will find in rock formed millions of years ago!
Thorton
ReplyDelete“All the parts - bones, muscle, blood vessels - develop simultaneously, in parallel, based on the DNA in the original zygote.”
I think I understand now. For example wing size and everything else is set or decided at genetic level at the early stages of organism development. Once organism grows to its full size mutations only work to kill it in spite of all the DNA repair mechanisms. That’s called getting older.
Early stages of development seem critical and here we see the process of gene regulation is controlling the future physical structure. Animal’s (or organism’s) structure is stored (contained, represented) in the lengths of the DNA string - genes. I would say that process has full control in this development so I would consider it a higher “command” level, which in a control system is always abstracted because it deals with representations of a concrete, real setup.
Process can manipulate representations in a limited way, I wouldn’t think it has a full freedom. For example, it wouldn’t replace head with a leg. Rather, process (of gene regulation) is making small limited changes and combinations at the gene level ant that affects the future structure of an animal or organism.
I think this is a type of system where environment presents problem and gene regulation probes for solution. There is no direct feedback except what survives environmental challenge appears to be a good solution.
Eugen
DeleteI think this is a type of system where environment presents problem and gene regulation probes for solution. There is no direct feedback except what survives environmental challenge appears to be a good solution.
So we get random genetic variations that cause differences in morphology. Then those different morphologies are subjected to selection pressure by the environment. The more successful forms (on average) live to reproduce and pass on their successful genes better than the less successful ones. The process is iterative which causes the successful changes to spread through the population.
Now if only we could come up with a catchy name for such a process. :)
Have you read Weiner's "The Beak of the Finch"? Is that what happens on the Galapagos Islands?
DeleteEugen: For example wing size and everything else is set or decided at genetic level at the early stages of organism development. Once organism grows to its full size mutations only work to kill it in spite of all the DNA repair mechanisms. That’s called getting older.
ReplyDeleteHeritability is not 100%, but heritable variations are the stuff of evolution. Cellular mutations are usually deleterious, but not necessarily so. Aging is still not fully understood, but it is apparently a programmed process, at least to some extent.
Didn't you hear of BEZT process, Blas-Eugen-Zachriel-Thorton process
ReplyDelete:D