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Convergence, another problem for evolution

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1 Convergence, another problem for evolution on Tue May 12, 2015 2:47 pm


Convergence, another problem for evolution

Evolutionists assert that convergence results when unrelated organisms encounter nearly identical selection forces (environmental, competitive, and predatory pressures). Natural selection then channels the random variations believed to be responsible for evolutionary change along similar pathways to produce similar features in unrelated organisms.

One of the challenges that convergence creates for the evolutionary paradigm is the frequency with which it occurs throughout life’s history. Convergence is a common characteristic of life. This commonness makes little sense in light of evolutionary theory. If evolution is indeed responsible for the diversity of life, one would expect convergence to be extremely rare.  The mechanism that drives the evolutionary process consists of a large number of unpredictable, chance events that occur one after another. Given this mechanism and the complexity and fine-tuning of biological systems, it seems improbable that disparate evolutionary pathways would ever lead to the same biological feature.4

Two remarkable examples of complex biological features recently recognized as being convergent are bat echolocation (the ability of an organism to orient itself based on perceiving reflections of sound it emits) and parrot, songbird, and hummingbird forebrain structure. A recent DNA sequence analysis has just confirmed two earlier studies that, from an evolutionary perspective, requires echolocation in bats to have evolved independently in two separate groups (microchiroptera and megachiroptera).5-7  This study, along with previous analyses also indicate that the strikingly similar limb structures of bats and flying lemurs used for flying, likewise, must have evolved independently, when the data is interpreted from an evolutionary perspective.

Even more challenging for the evolutionist are the cases in which convergence occurs in organisms from radically different environments. Under these circumstances, the forces that comprise natural selection must be different by definition. The classic example of this type of convergence is found in the eye structure of the cephalopods (nautili, cuttlefish, squids, and octopods).10 Their similarity to vertebrate eyes is remarkable from an evolutionary perspective, given that 1) mollusks, which include cephalopods, are classified as a member of a fundamentally different group (lophotrochozoan) than vertebrates (deuterostomes)11; and 2) the selective forces that would have shaped the formation of both the cephalopod eye and vertebrate eye must have been quite different. Evolution would have required an aquatic environment for the cephalopods and a primarily terrestrial environment for the vertebrates.

An even more remarkable example of convergence occurring in aquatic and terrestrial environments can be seen in the sandlance (fish) and chameleon (reptile), respectively. Recent experiments have uncovered an extraordinary similarity in the visual systems and behavior for these two creatures.12-15 Both the chameleon and the sandlance move their eyes independent of one another in a jerky manner, rather than in concert. While one eye is in motion the other eye is motionless. Moreover, both animals use the cornea of the eye to focus on objects. All other reptiles and fish use the lens of the eye to focus images on the retina. The chameleon and sandlance both rely on a specialized muscle (the cornealis muscle) to adjust the focusing of the cornea. The chameleon determines depth perception using a single eye. Scientists believe the sandlance also determines depth perception in this manner. Both the sandlance and the chameleon have skin coverings over their eyes to prevent them from being conspicuous to both predators and prey. The feeding behavior of both animals is also the same. The trajectory that the chameleon tongue takes when attacking its prey is the same as that taken by the sandlance when it lunges for its prey. (The sandlance buries itself in sand beds with its eyes above the surface of the sand and waits for tiny crustaceans to pass by.)

Convergence, another problem for evolution

Biologists are uncovering numerous examples of organisms that cluster together morphologically (structurally), and yet are genetically distinct. Frogs, lizards, or herbs that appear to be identical are actually different at the genetic level. An evolutionary interpretation of this data, then, demands that the morphologically identical organisms must have evolved independently of one another in a “repeatable” fashion.

“…No finale can be specified at the start, none would ever occur a second time in the same way, because any pathway proceeds through thousands of improbable stages. Alter any early event, ever so slightly, and without apparent importance at the time, and evolution cascades into a radically different channel.1

Stephen J. Gould, Wonderful Life: The Burgess Shale and the Nature of History (New York, NY: W.W. Norton & Company, 1989), 51.

Gould’s metaphor of “replaying life’s tape” asserts that if one were to push the rewind button, erase life’s history, and let the tape run again, the results would be completely different.2 The very essence of the evolutionary process renders evolutionary outcomes as nonreproducible (or nonrepeatable). Therefore, “repeatable” evolution is inconsistent with the mechanism available to bring about biological change.

Paleontologist J. William Schopf, one of the world’s leading authorities on early life on Earth, has made this very point in the book Life’s Origin.

Because biochemical systems comprise many intricately interlinked pieces, any particular full-blown system can only arise once…Since any complete biochemical system is far too elaborate to have evolved more than once in the history of life, it is safe to assume that microbes of the primal LCA cell line had the same traits that characterize all its present-day descendents.

Gould’s famous tape of life would be very different if replayed, even more different than Gould might have imagined.”

Evolutionary theorist Stephen Jay Gould is famous for describing the evolution of humans and other conscious beings as a chance accident of history. If we could go back millions of years and “run the tape of life again,” he mused, evolution would follow a different path.

Further readings :

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Converging on an Explanation

Using echolocation, bottlenose dolphins and some (though not all) bats scout their dark or murky surroundings with high-pitched “shouts” that bounce back full of information. That information tells these animals how to avoid obstacles and home in on their dinner. Bats and dolphins are assigned to vastly divergent branches of the evolutionary tree. Therefore, evolutionary scientists believe they independently—convergently—evolved the ability to produce, detect, and interpret ultrasonic waves.

Convergence is the evolutionary explanation invoked to explain obvious phenotypic similarities in animals of different lineages. Convergent evolution is the notion that when organisms whose ancestral paths have not recently crossed possess a similar feature (phenotype), they evolved that feature independently to cope with similar challenges.

Presumably, the random road of genetic evolution would not tend to travel the same way twice, particularly to produce complex traits in animals of different lineages.

Humans share vocalization structures 80% the same as song birds, apes have zero.

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Evolutionists Hear Whopping Case of Convergent Evolution

You won’t believe your ears when you hear what a team of evolutionists claims evolved by “convergent evolution.”
The sense of hearing would easily qualify as one of the most complex of senses, not that the others aren’t too. But to imagine the eardrum, the finely-tuned ossicles of the mammalian middle ear, and the cochlea with its “piano keyboard” of frequency sensors, evolving by chance would surely represent a major challenge to evolution. Now, however, a team of evolutionists just claimed in Science Magazine a case of “Convergent Evolution Between Insect and Mammalian Audition.” A katydid in a rainforest has an analogous 3-part mechanism for hearing, despite diverging from the common ancestor back in the Cambrian period, according to the evolutionary timeline. The abstract states confidently,
In mammals, hearing is dependent on three canonical processing stages: (i) an eardrum collecting sound, (ii) a middle ear impedance converter, and (iii) a cochlear frequency analyzer. Here, we show that some insects, such as rainforest katydids, possess equivalent biophysical mechanisms for auditory processing. Although katydid ears are among the smallest in all organisms, these ears perform the crucial stage of air-to-liquid impedance conversion and signal amplification, with the use of a distinct tympanal lever system. Further along the chain of hearing, spectral sound analysis is achieved through dispersive wave propagation across a fluid substrate, as in the mammalian cochlea. Thus, two phylogenetically remote organisms, katydids and mammals, have evolved a series of convergent solutions to common biophysical problems, despite their reliance on very different morphological substrates.
Detecting the mechanism of katydid hearing was never possible in such detail before. The cochlear analogue in the katydid, which they named the “acoustic vesicle,” is so small (600 millionths of a meter), it required x-ray microtomography and other state-of-the-art techniques to elucidate its structure. Yet in a remarkable diagram, the authors compared the three parts of a human ear and katydid ear side by side, showing how analogous the structures are.
Physiologists know that “Cochlear hair cells receive mechanical inputs at specific frequencies, depending on their position along the stiffness gradient of the basilar membrane. This ‘piano keyboard’ mapping, or tonotopic organization, is the canonical mechanism for frequency selectivity in mammals.” What would they think of a comparable piano keyboard mechanism in the ear of an insect?
The authors preached the convergence theme with repetition, stating it six times, including the headline. For example, they said, “Our results reveal a notable case of convergence, whereby organisms with the most remote phylogenetic histories (such as mammals and katydids), have evolved to hear in a markedly analogous way.” Ronald R. Hoy chimed right in with the convergence chorus in his Perspectives piece, “Convergent Evolution of Hearing,” in the same issue of Science. He said that the researchers “show that although the hearing organ of a rainforest insect looks very different from a human ear, it can be divided into the same three functional entities, providing evidence for convergent evolution.”
Later, New Scientist jumped on the “convergent evolution” bandwagon without missing a beat. The article quoted a Cambridge biologist not involved in the study saying, “This is an amazing example of convergent evolution in hearing structures between very distantly related animals.”
None of the authors thought to consider this new evidence as a challenge to evolution. Instead, they treated the convergence concoction as demonstrable fact. “The parallelism in anatomy and function is the result of convergent evolution between the ears of humans and katydids. It is as surprising as it is remarkable,” Hoy said.
One can imagine fairy tales, too, that are surprising and remarkable. Did evolutionary theory predict this? No. This was a surprise. It was a remarkable surprise. If you had trouble imagining a blind, aimless process producing a super-sensitive vibrating drum attached to a series of intricate levers that connect to a piano keyboard frequency analysis system, transducing acoustic energy into mechanical energy and then into fluid energy, increasing sensitivity at each step – if you can imagine evolution producing all that once, now imagine it happening twice.
This goes to show that evolutionists believe in miracles. Natural selection is their “Abracadabra” to generate sophisticated systems in living things. No demonstration is required; no one gets to look behind the curtain and follow the train of random mutations from deaf cell to hearing animal. If Abracadabra doesn’t work the first time, say it with emphasis, adding Mishikabula, Bippity Boppity

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4 Re: Convergence, another problem for evolution on Wed Jun 17, 2015 11:20 am



Homology, convergence and parallelism

Similarities in the structure, physiology or development of different species are said to be homologous if they are attributable to descent from a common ancestor. For instance, the forelimbs of humans, whales, dogs and bats are regarded as homologous, i.e. derived from an ancestor with similarly arranged forelimbs. Corresponding features with similar functions that are not thought to have originated by common descent are said to be analogous (or homoplasious). Examples are the wings of birds and flies, which are believed to have developed independently.
‘Homologous’ structures are supposed to have initially originated by the random accumulation of tiny advantageous mutations, and then to have been inherited by descendant species and further adapted, thanks to natural selection of further random mutations. ‘Analogous’ structures, on the other hand, are supposed to have arisen by random mutations several times and entirely independently – this is called convergent or parallel evolution. Parallel evolution refers to the appearance of similar patterns in more or less closely related plant and animal species, while convergent evolution refers to the appearance of striking similarities among organisms only very distantly related, but the boundary between the two terms is blurred.
Convergent evolution demonstrates that similarity does not always imply homology, i.e. inheritance from a common ancestor. There are many cases where similar features once classed as homologous have later been reclassified as analogous. Moreover, traits controlled by identical genes are not necessarily homologous and homologous structures need not be controlled by identical genes. Regulatory genes that are considered homologous may be dedicated to non-homologous morphology. There are many examples where homologous structures develop via completely different embryological routes. For instance, the alimentary canal is formed from the roof of the embryonic gut cavity in sharks, from the floor in the lamprey, from the roof and floor in frogs, and from the lower layer of the blastoderm in birds and reptiles.1
There are hosts of convergences in the plant world. Very similar leaf patterns, for example, have appeared again and again in separate genera and families. Green plants depend for their survival on photosynthesis, whereby sunlight is used to convert water and carbon dioxide into energy-rich carbohydrates. 3% of plants use C4 photosynthesis, in which CO2 is first fixed into a four-carbon acid with the aid of an enzyme called PEPC. These acids then diffuse to the cells in an airtight structure known as the bundle sheath, where they are broken down into CO2 molecules, after which photosynthesis proceeds as normal. This highly complex and efficient process allows plants to grow faster and use less water. According to Williams et al., ‘C4 photosynthesis has independently evolved from the ancestral C3 pathway in at least 60 plant lineages, but, as with other complex traits, how it evolved is unclear.’2

Fig. 5.3. Three species of South American butterflies which closely mimic each other, even though they belong to distinct families: Melinaea lilis imitataHelinconius ismenius telchiniaDismorphia amphione praxinoe.3 Many close similarities are found in the wing colouration patterns of butterflies, both within and between families.

Fig. 5.4. Convergent evolution of the raptorial foreleg of the praying mantis and an insect known as Mantispa. It is derived from a generalized insect leg, modified for catching and grasping prey. It also evolved independently in a third group of insects, the rhachiberothidids.4

A striking example of convergent evolution is provided by the two main branches of the mammals, the placentals and marsupials, which have supposedly followed independent evolutionary pathways, after splitting off from some primitive mammalian common ancestor in the late Cretaceous. (Placentals bear their young fully developed, while marsupials give birth prematurely and nurture their young in a pouch.) The marsupials of Australia have evolved in isolation from placental mammals elsewhere yet have given rise to a whole range of similar forms: pouched versions of anteaters, moles, flying squirrels, cats, wolves, etc. Much the same phenomenon occurred in South America, where marsupials independently gave rise to a range of parallel forms.


Fig. 5.5. Examples of convergence: placental and marsupial mouse, placental wolf and marsupial Tasmanian wolf, marsupial flying phalanger and placental flying squirrel.

Fig. 5.6. Convergence in the sabre-tooth: drawing by Carl Buell of the placental Smilodon (top) and the marsupial Thylacosmilus.5

The eye has appeared many times in unrelated groups of animals. There are two main types of eye: the compound eye found in arthropods, and the camera eye. The camera eye has evolved independently at least seven times – in mammals (e.g. humans), cephalopods (e.g. squid and octopus), certain annelid worms, cubozoans (a form of jellyfish), and three separate forms of snail. Wings allegedly evolved independently no less than four times: in insects, flying reptiles, birds and bats. Electrogeneration in fish has appeared independently at least six times and in each case involved the modification of muscle cells. Bioluminescence – the ability of creatures to produce their own light with chemicals – is said to have evolved independently 40 to 50 times. The whale, dolphin, extinct ichthyosaurus of the Mesozoic, and shark all look similar, yet the shark is a fish, the ichthyosaurus was an aquatic reptile, and the whale and dolphin are mammals. Other convergences include the production of silk threads by spiders, silk moths, larval caddis flies and weaver ants, sonar-like echolocation systems in microbats, toothed whales and shrews, and warm-bloodedness in birds, mammals and certain fish.

Fig. 5.7. Convergence of the camera eye in humans (vertebrate) and the octopus (cephalopod). The eyes are ‘wired’ differently: in humans light passes through the nerves on the way to the photoreceptors (retina), whereas in the octopus it does not. 1 = retina; 2 = nerve fibres; 3 = optic nerve; 4 = blind spot in humans, caused by nerve fibres passing through the retina.

Palaeobiologist Simon Conway Morris has catalogued the extraordinary variety of convergences in animals and plants. He says that the extent and importance of convergence have been consistently underestimated, and that most examples are known only to specialists. Descriptions of convergences are full of adjectives like ‘remarkable’, ‘striking’, ‘extraordinary’, ‘astonishing’ and ‘uncanny’. Morris says that ‘there is almost a feeling of unease in the similarities’, and that some biologists ‘sense the ghost of teleology looking over their shoulders’. Life, he says, ‘shows a kind of homing instinct’;6 the ubiquity of convergence ‘means that life is not only predictable at a basic level, it also has direction’.7 But he has no explanation other than the standard neo-Darwinian tale that similar forms and structures evolve because random mutations are sifted by similar selection pressures, and because there may be only a very limited number of ways of solving particular challenges (e.g. designing an eye). However, it is difficult enough to imagine how a complex organ or organism could have evolved even once by a combination of thousands of randomly generated ‘beneficial’ mutations; the idea that it could have happened more than once beggars belief. Moreover, when related species independently evolve similar physical traits they sometimes use the same genes to do so – which deals a further blow to the idea that evolution is essentially a random process.8
Numerous examples from the fossil record therefore suggest that particular evolutionary pathways are repeated: organisms with features almost identical to previous species appear again and again. Instead of thinking in terms of random mutations, it seems more reasonable to suppose that records of past features and structures are stored in some way, and that these records can be tapped into and modified during the design of later creatures.

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Theory of Convergent Evolution Analyzed 1

The knifefish, rather than having several fins like a trout, has one long "ribbon fin" that undulates along the length of its body. Studies of its motion reveal that it uses the optimal wavelength to get the most forward thrust, stability, and maneuverability out of its investment of energy. But the knifefish is not alone: the same optimal design can be found in cuttlefish (cephalopods), rays (cartilaginous fish), certain flatworms, and other bony fish that are evolutionarily unrelated. In fact -- if evolution by natural selection is assumed to be the cause -- this design emerged independently at least eight times. To the Darwinian, it's another remarkable case of "convergent evolution."
A paper in PLOS Biology investigates this phenomenon and tries to explain it. The five authors, primarily from Northwestern University, used a robotic knifefish to nail down the physical factors related to optimal swimming design: the length of the fin's undulation and the mean amplitude. Dividing the one by the other yields what they call the Optimal Specific Wavelength (OSW). Then they measured the OSW on 22 live swimmers, such as cuttlefish and rays, to see how they rated. They found that the values "converge to a narrow range" around 20, even though the animals belong to eight separate groups whose presumed ancestors did not possess this kind of propulsion. Robin Meadows says in a companion piece likewise in PLOS Biology:

Many OSW swimmers have no known ancestor that swam with median/paired fins, and the 22 species in this analysis belong toeight clades (groups of organisms stemming from a common ancestor). This suggests that the OSW evolved independently at least eight times. [Emphasis added.]

Casey Luskin has argued that Darwinians appeal to convergence in order to have it both ways: basically, "biological similarity implies common ancestry, except when it doesn't." The authors of this new paper do not respond to that charge specifically, but they go further than most Darwinians by not just asserting convergence occurred, but by offering evolutionary mechanisms that might produce it. They begin with broad philosophical questions:

How would life look if it evolved again on Earth, or for that matter, on any other habitable planet? The question of the role of chance versus necessity in evolution is a foundational issue in biology.Gould gave us the metaphor of the "tape of life" for the evolution of life and argued that if it were somehow rewound and started again, life would have taken a very different course. Conway Morris has argued that, on the contrary, the laws of physics limit the number of good solutions that are within reach of evolution, and that therefore we should expect life to take a similar course upon rewinding. Examples of convergent evolution, such as wings on insects, birds, and mammals, are considered supporting evidence for this hypothesis. But our understanding of convergent evolution, as reflecting the dominance of natural selection plus variation over factors such as developmental constraints, pleiotropy, phylogenetic inertia, genetic drift, and other stochastic processes, is held back by a lack of quantitative arguments. Such arguments would exposethe links from physical principles to the biological phenomena and help us understand where evolution is likely to converge to the same result or diverge to a wide variety of solutions.
Here, we present just such arguments for a phenomenon thatunifies a vast diversity of swimming organisms, from invertebrates, like cuttlefish, to vertebrates, like cartilaginous and bony fish. Unlike the case of the convergently evolved wing, a morphological feature, here the evolved feature is a pattern of movement that occurs across a morphologically diverse set of moving appendages on aquatic animals.

We see at once that the implications go far beyond the knifefish's OSW. Evolutionary theory itself is at stake: Is it truly contingent, or somehow directed? Their argument hinges on the ability of the environment (e.g., the properties of water) to direct natural selection so that it rewards, with higher fitness, the animals that hit the optimum. If the OSW is on a peak of the fitness landscape, natural selection will drive an animal up the peak, no matter its ancestry, because it will outcompete the others. That's how separately evolving animals will end up (converge) on the same fitness peak.

What is the mechanism for macroevolutionary repeatability? In the language of the calculus of variations, these examples of convergent evolution -- if correctly identified as such -- imply that there is agradient in the fitness landscape toward some optimum with respect to trait in question, and this gradient is large enough to overcome competing factors such as developmental constraints, pleiotropy, phylogenetic inertia, genetic drift, cases where optimality in one trait results in suboptimality in another trait ... and approximations of the trait which provide local but not global optimality. With asufficiently steep gradient in fitness in place and evolutionary dynamics capable of achieving near-optimal solutions, it is only a matter of time before the mechanism of selection with variation can arrive at the optimum. As the derivative of the trait with respect to fitness is stabilizingdepartures from the optimum would be self-correcting over evolutionary time.

In fulfillment of the promise of quantifying their argument, they measure the loss in force for wavelengths that deviate significantly from the OSW. "The effect of any decline in propulsive force -- even less than one percent -- from what it is at the OSW is amplified over the vast number of undulations an animal may make in its life," they argue. What animal would want to compete with less than the best?
Unfortunately, undulating fins are not the best. Tuna are the fastest swimmers in the ocean, but they rely on their caudal fins to thrust their bodies forward. So we have a conundrum; "The question is therefore why the slower forms of swimming exhibited by median/paired fin animals would emerge and thrivedespite the prevalence of body/caudal fin swimming in ancestral species." Why would evolution switch from the Ferrari to the Volkswagen?
The authors are ready with auxiliary hypotheses:

A similar question has arisen in simulation studies that show that alight-sensitive patch of skin can evolve through several intermediate forms into an advanced camera-type lens eye in only a few hundred thousand years -- why, then, are there so many existing animals with intermediate forms of eyes? Nilsson and Pelger's answer is that camera-type lens eyes are only the best solution for certain animal -- ecosystem combinations. Our answer is similar: body/caudal fin swimming makes little sense in isolation. It is only within particular ecological contexts that some types of animals are able to survive better with this type of swimming than with alternative approaches.
In particular, median/paired fin swimming appears to be a low speed, low cost of transport specialization. The lower amplitudes of fin movement that are possible in median/paired fin swimmers, compared to the very high amplitudes possible when the high power axial musculature is used in body/caudal fin swimmers, is thereforean advantage instead of a liability due to the lower energetic costof transport of median/paired fin swimming. The fact that median/paired fin swimming is used at lower speeds should not be confused, however, with the concept of maximizing speed by swimming at the OSW. Even when swimming at lower speeds (or whatever speed for that matter, which is determined by frequency and amplitude), for a given set of parameters (amplitude of undulations, frequency, fin height, and fin shape), if an animal swims with elongated median/paired fins, then its speed can be maximized for that set of parameters by swimming at the OSW.

Our regular readers will jump at that lateral pass to Nilsson and Pelger. Their claim about the evolution of camera eyes was thoroughly trounced by David Berlinski almost a decade ago in these pages. It's an example of how scientists can continue to trust flawed arguments for years -- decades, sometimes -- without considering (or even knowing about) the counter-arguments.
Aside from that, the authors make a point: You can't just look at a fin in isolation. You need to consider the ecological niche of the animal. They point to members of the group Gymnotiformes, electric fish who use their ribbon fins in low-oxygen murky waters, that swim mostly at night where high speed is not advantageous.

Given these constraints, the elongated fins that are universally present within the more than 150 species comprising Gymnotiformesmay be favored, but clearly a tremendous amount of work would need to be done to assess the relative importance of all of these factors in giving rise to this one group of median/paired fin swimmers.
While the existence of body/caudal fin swimmers and the existence of median/paired fin swimmers may or may not be subject to robust repeatability, what is clear is that if median/paired fin swimming with elongated fins and semirigid trunks emerges -- as ithas independently on multiple occasions according to Fig 1 -- it is very probable that the specific trait of swimming at the OSW will also emerge.

This is a very different claim, much reduced from the original one. No longer are they asserting that the environment will force different swimmers up the same fitness peak, because clearly it didn't for the tuna. Now we have the more modest claim that "if" a ribbon fin "emerges," then natural selection will push it toward the OSW. But where is their scientific law of emergence? What about the ocean environment can cause that? And we see they just admitted that their hypothesis "may or may not be subject to robust repeatability."
Another complication is that some of the undulating-fin fish can switch to high-speed caudal-fin swimming when needed, as when under attack from predators or when zooming in on prey. Why would natural selection provide both methods of propulsion? The fitness landscape just got more complicated; the animal has to climb multiple fitness peaks to survive. (We might point out, in passing, that according to evolutionists, electric organs are examples of convergence, too, having evolved six times independently according to a report last year from the University of Wisconsin posted at NewsWise.)
Notice, also, that while the ecological hypothesis seems to work for the Gymnotiformes, it doesn't for the others. Rays and cuttlefish, for instance, use their undulating fins in the open sea or coastal shallows during the daytime. The authors have not shown that their auxiliary hypotheses rescue convergent evolution, nor have they identified any evolutionary mechanism to account for fast swimmers with caudal fins swimming right alongside slow swimmers with undulating fins in the exact same watery environment. Every proposal has exceptions; where is that quantitative argument, exactly?

Thus, we can only speculate that the 7.5% decline in force occurring over the observed variation in SW is not large enough to overcome the many causes of suboptimality listed above, whereas the 25% decline we find beyond this range is large enough to cause selection pressure toward the OSW. Additional research is needed to establish whether this hypothesis is true.

We thus circle back to Casey Luskin's challenge: Common ancestry explains traits, except when it doesn't.
For these reasons, we cannot take Robin Meadows's praise of this paper seriously:

This elegant work reveals that a physical problem -- how to get from here to there -- can be optimized by a wondrous diversity of biological solutions. Moreover, these findings strengthen the case that mechanical optimization can drive evolution, contributing to the longstanding debate over the evolutionary roles of randomness versus physical constraints that limit the solutions that are feasible in living creatures. As the researchers point out, quantifyingphysical properties that underlie biological phenomena could helpus recognize when an optimal mechanical solution is likely to drive convergent evolution.

Ockham is tapping his foot by the door.


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Convergent Evolution Challenges Darwinism and Destroys the Logic Behind Common Ancestry

The problem for evolutionary biologists faced with conflicting evolutionary trees is that biological similarity often appears in places not predicted by common descent. In other words, everyone recognizes that biological similarities often appear among species in cases where they cannot be explained as the result of inheritance from a common ancestor. This means the main assumption fails.
We also saw at the end of Problem 6 that when biologists are unable to construct phylogenetic trees, they often make ad hoc appeals to other processes to explain away data that won't fit a treelike pattern. One of these explanations is convergent evolution, where evolutionary biologists postulate that organisms acquire the same traits independently, in separate lineages, and not through inheritance from a common ancestor. Whenever evolutionary biologists are forced to appeal to convergent evolution, it reflects a breakdown in the main assumption, and an inability to fit the data to a treelike pattern. Examples of this abound in the literature, but a few will suffice.
Genetic Convergent Evolution
A paper in the Journal of Molecular Evolution found that molecule-based phylogenies conflicted sharply with previously established phylogenies of major mammal groups, concluding that this anomalous tree "is not due to a stochastic error, but is due to convergent or parallel evolution."119
A study in Proceedings of the U.S. National Academy of Sciences explains that when biologists tried to construct a phylogenetic tree for the major groups of birds using mitochondrial DNA (mtDNA), their results conflicted sharply with traditional notions of bird relationships. They even found "convergent" similarity between some bird mtDNA and the mtDNA of distant species such as snakes and lizards. The article suggests bird mtDNA underwent "multiple independent originations," with their study proposing "multiple independent origins for a particular mtDNA gene order among diverse birds."120
A 2005 paper in Nature Immunology observed that plants and animals have a highly similar biochemical organization of their respective innate immune systems, but their common ancestor didn't have such an immune system:
Although it seems to be generally accepted that the innate immune responses of plants and animals share at least some common evolutionary origins, examination of the available data fails to support that conclusion, despite similarities in the overall 'logic' of the innate immune response in diverse multicellular [organisms].121
According to the paper, common descent cannot explain these "unexpectedly similar" systems, "suggesting independent evolutionary origins in plants and animals." The paper is forced to conclude that such complex similarities make for a "compelling case for convergent evolution of innate immune pathways."122
Another famous example of convergent evolution is the ability of bats and whales to use echolocation, even though their distant common ancestor did not have this trait. Evolutionary biologists long-believed this was a case of morphological convergence, but an article in Current Biology explains the "surprising" finding that echolocation in bats and whales also involves geneticconvergence:
Only microbats and toothed whales have acquired sophisticated echolocation, indispensable for their orientation and foraging. Although the bat and whale biosonars originated independently and differ substantially in many aspects, we here report the surprising finding that the bottlenose dolphin, a toothed whale, is clustered with microbats in the gene tree constructed using protein sequences encoded by the hearing gene Prestin.123
One paper called this data, "one of the best examples of convergent molecular evolution discovered to date."124 But again, these are hardly isolated examples. In 2010, a paper in Trends in Genetics explained:
The recent wide use of genetic and/or phylogenetic approaches has uncovered diverse examples of repeated evolution of adaptive traits including the multiple appearances of eyes, echolocation in bats and dolphins, pigmentation modifications in vertebrates, mimicry in butterflies for mutualistic interactions, convergence of some flower traits in plants, and multiple independent evolution of particular protein properties.125
Biochemist and Darwin-skeptic Fazale Rana reviewed the technical literature and documented over 100 reported cases of convergent genetic evolution.126Each case shows an example where biological similarity -- even at the genetic level -- is not the result of inheritance from a common ancestor. So what does this do to the main assumption of tree-building that biological similarity implies inheritance from a common ancestor? With so many exceptions to the rule, one has to wonder if the rule itself holds merit.
The Earth is Round, But Is Common Ancestry True?
One evolutionary scientist tried to pressure his readers into accepting Darwinism by claiming "biologists today consider the common ancestry of all life a fact on par with the sphericity of the earth."127 But are such categorical statements even helpful, much less true?
Proponents of neo-Darwinian evolution are forced into reasoning that biological similarity implies common ancestry, except for when it doesn't. And in the many cases where it doesn't, they appeal to all sorts of ad hoc rationalizations to save common ancestry.
Tellingly, the one assumption rarely questioned is the overall assumption of common ancestry itself. But perhaps the reason why different genes are telling different evolutionary stories is because the genes have wholly different stories to tell, namely stories that indicate that all organisms are not genetically related. There is some hope for a different story more attuned to the data, as Michael Syvanen dared to suggest in Annual Review of Genetics in 2012, that "life might indeed have multiple origins."128 In other words, universal common ancestry may in fact, not be true.

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if you would understand the argument, i am sure you would have searched another one easyer to attack. 

Convergent genetic evolution, basically asserts that the same gene sequence evolved several times in different linages. If the evolution of one functional gene in sequence space is rare , how much rarer, the same feat happening not only once, but several times ?

In a article in Nature, the author admitted:

Convergent evolution seen in hundreds of genes
Bats and dolphins may have developed echolocation via similar mutations

A new analysis suggests that many genes evolved in parallel in bats and dolphins as each developed the remarkable ability to echolocate. The team found a 'convergence signature' in nearly 200 regions of the genome. Genes involved in hearing were more likely to have evolved similarly across species than those involved in other biological traits. Some genes involved in vision were also among those bearing the strongest signal of convergence — a surprising result.

In sciencedaily they write:

We had expected to find identical changes in maybe a dozen or so genes but to see nearly 200 is incredible. We know natural selection is a potent driver of gene sequence evolution, but identifying so many examples where it produces nearly identical results in the genetic sequences of totally unrelated animals is astonishing.

The outcome of this is, you can bury the fairytale story you believe in, that is common descent, its not necessary anymore. You had to say that the similarities evolved independently rather than by common descent, via  convergent evolution.

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Examples of Convergence

Mole Cricket
Tasmanian wolf

Crocodile a-hemoglobin
Human lysozyme
Ladder web

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Convergence of the cuttlefish and chamaeleon is particulary interesting.  Both use

Last edited by Admin on Tue Aug 29, 2017 8:01 am; edited 1 time in total

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10 Re: Convergence, another problem for evolution on Tue Aug 08, 2017 5:44 pm


The evolutionary biology of the Bivalvia, at the level of both zoology and paleontology, provides multiple examples of convergence and parallel evolution, a fact that makes the interpretation of their evolutionary history difficult (Harper et al., 2000).

The northern sea cod (Boreogadus saida) is an economically important marine fish of the family Gadidae found on both sides of the North Atlantic. The distantly related order Perciformes with its suborder Percoidei contains the sea basses, sunfishes, perches, and, more relevant to our interest, the notothenioid fishes from the Antarctic (Dissotichus Mawson). In spite of their distant relationship with cods, they have evolved the same type of antifreeze proteins, in which the amino acids threonine, alanine, and proline repeat (Chen et al., 1997). These proteins are active in the fish’s blood and avoid freezing by preventing the ice crystals from growing.

The blind cavefish Astyanax fasciatus are sensitive in two long-wavelength visual pigments.  The mammalian lineages diverges, but fish multiple wavelength- sensitive green and red pigments exist. Genetic analysis demonstrates that the red pigment in humans and fish are independent of the green pigment by a few identical amino acid substitutions, a clear case of convergence at the molecular level.

Convergence may also occur when the sequence and structure of molecules are very different, but the mechanisms by which they act are similar. Serine proteases have emerged independently in bacteria (e.g. subtilisin) and vertebrates (e.g. trypsin). Despite their very different sequences and three-dimensional structures, in each the same set of three amino acids form the active site. The catalytic triads are His57, Asp102, and Ser195 (trypsin)
and Asp32, His64, and Ser221 (subtilisin) (Doolittle, 1994; A. Tramontano, personal communication).

Specific examples of convergence in mollusks have been pointed out in various families of the gastropods (camaenid, helminthoglyptid, and helcid snails). The shells of the camaenid snails from the Philippines and the helminthoglyptid snails from Central America resemble each other and also members of European helcid snails. These distant species, in spite of having quite different internal anatomies, have grown to resemble each other morphologically in response to their environment. In other words, in spite of considerable anatomical diversity, mollusks from these distant families have come to resemble one another in terms of their external calcareous shell (Tucker Abbott, 1989, pp. 7–Cool.

1. Barrow, FITNESS OF THE COSMOS FOR LIFE,  Biochemistry and Fine-Tuning, page 159

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