Convergent evolution? Crown of Thorns starfish shows “surprising” chordate-like gene organization

_{Denyse O'Leary

December 17, 2014

Convergent evolution, Genomics, Intelligent Design}

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An intact Hox cluster. From ScienceDaily:

New research published in the journal genesis, by Kenneth Baughman, Dr. Eiichi Shoguchi, Professor Noriyuki Satoh of the Marine Genomics Unit at the Okinawa Institute of Science and Technology Graduate University, and collaborators from Australia, reports an intact Hox cluster in the Crown of Thorns starfish, Acanthaster planci. This surprising result contrasts with the relatively disorganized Hox cluster found in sea urchins, which are also echinoderms, classification of animals including starfish, sea lilies, and sea cucumbers. Stanford University Professor Christopher Lowe, who studies developmental biology in echinoderms, summarizes the paper: “The translocation of the Hox cluster in echinoderms has been a major red herring for understanding their evolution. It’s really good to have some hard data showing that some echinoderms exhibit some oddities that are not representative of all echinoderms.”

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Generally, the Hox cluster shows “colinearity,” in which gene order correlates with the location of expression, or the developmental stage of expression. “For example, anterior Hox genes are expressed in regions that are closer to the head of an embryo, and are expressed sooner during development, versus the posterior Hox genes,” explained Baughman. “Thus, we were surprised to see chordate-like Hox cluster organization in starfish, which have a radial body plan.” Echinoderms are classical model organisms for embryology, and more recently evo-devo. Baughman added, “Interacting with the speakers and students of theOIST Winter Course ‘Evolution of Complex Systems’ (OWECS) allowed me to appreciate the importance of finding an intact Hox cluster in starfish.”

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By the way, it is a pretty remarkable life form anyway.

Comments

AVS:
Like I already said Mungy, we do know what makes an organism what it is: it’s genome and the differential gene expression of that genome.
Evidence please. The typical propaganda means nothing without evidence.
Yes, Joe, what are your thoughts on why dolphins and whales have such large brains in comparison to body size?
Intelligent design
Why not just increase gill size so as to have a larger surface area for gas exchange?
LoL! As if that will put O2 in the water. There are water-worlds which lack dissolved O2 and the fish are air-breathers- see the the Arapaima of the Amazon
The large brains of dolphins and whales can’t be due to the evolution of these species from ancestral mammals could it?
There isn't any evidence that such a transformation is possible. So that would be a problem.Joe_{December 26, 2014
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The theory of evolution doesn't exist so no, it does not provide a robust explanation. Zachriel is just another insipid troll.Joe_{December 26, 2014
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CharlieM: Can you tell us what that niche is? Intelligent, tool-using, social apes. CharlieM: Pick any species with an opposable thumb and tell me what they have achieved by using this feature and let us see how it compares with human achievement. Human achievement? Humans are the only organism with opposable thumbs to build skyscrapers, but not the only one to wage war. CharlieM: On its own the possession of an opposable thumb does not count for much. It was your example. CharlieM: Why has the pentadactyl limb persisted throughout the evolution of land vertebrates? Common descent. CharlieM: ... Individuals build nests in preparation for the coming of their offspring... Sure. Zachriel: Do you have scientific evidence of any sort to support your conjecture? CharlieM: you say that when looking at the larger scale of the history of life, everything changes and this does not apply. Notably, you didn't answer the question. CharlieM: What reasons do you have for thinking that it does not apply? Because the Theory of Evolution provides a robust explanation without having to make such extraneous suppositions. The primary mechanisms are common descent, natural selection, reproductive isolation, and extinction.Zachriel_{December 26, 2014
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Sorry my computer crashed and I seem to have lost the edit function on my last comment. Oh well! Seasons greetings to all.CharlieM_{December 26, 2014
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Hi Zachriel.
You wrote above: Of course there’s a niche.
Can you tell us what that niche is?
You wrote: Nor are humans the only organism with an opposable thumb.
Pick any species with an opposable thumb and tell me what they have achieved by using this feature and let us see how it compares with human achievement. On its own the possession of an opposable thumb does not count for much. But regarding the human organism as a whole it is ideally suited to creative work. A large brain, limbs freed from the task of support and/or locomotion, 'multiuse toosl' at the end of those limbs, the enhanced sense of touch at the ends of those 'tools'; all this and more taken together contribute to the creative capacity of humans. Why has the pentadactyl limb persisted throughout the evolution of land vertebrates? You might say that evolution must just use what it is given. Well I would say we are very fortunate that this limb was given in the first place. And all those specialists did not just use what they were given, but they changed the limb out of all proportion but it is still based on the original form.
I wrote: But this does not mean that it wasn’t prepared in advance for its use in present day humans.
You replied: You could conjecture so, but it seems contrary to what we have discovered about the history of life. Do you have scientific evidence of any sort to support your conjecture?
I would say that its only contrary to a biased, materialistic understanding of life. Preparing for the future is ubiquitous throughout all levels of life. To give some examples. Intra-cellular and intercellular transport moves pre-assembled molecules to places where they will be required in the future. The organism is pre-planned in the seed or the egg. Organisms ingest substances in advance of their need to build their structures and provide themselves with energy. Individuals build nests in preparation for the coming of their offspring. The tadpole is water dwelling, water breathing creature which is a preparation for an air breathing land dwelling amphibian. The, relatively unconscious, unaware baby is a preparation for the self conscious, aware adult. Species migrate, some of them over vast distances, in order to reach suitable breeding grounds. They do this in preparation for what will happen in the future. Everywhere we look life is in the process of preparing for what is to come. And you say that when looking at the larger scale of the history of life, everything changes and this does not apply. What reasons do you have for thinking that it does not apply?
CharlieM_{December 26, 2014
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lifepsy: Alleged convergence can’t even be identified until you demonstrate homology as a reference point. Homology is based on the assumption of the absence of convergence. That is incorrect. Homology is a determination based on evidence, not an assumption. Darwin: It is incredible that the descendants of two organisms, which had originally differed in a marked manner, should ever afterwards converge so closely as to lead to a near approach to identity throughout their whole organisation. lifepsy: Religious darwinian mysticism. Darwin's statement has been repeatedly supported by the evidence. Mung: Why would it “make more sense”? The nested hierarchy and fossil succession strongly support the evolution of the vertebrate limb. CharlieM: The human forelimb is the most general example of the pentadactyl limb found in vertebrates. It has no niche because it is capable of a multitude of functions. Of course there's a niche. Nor are humans the only organism with an opposable thumb. CharlieM: But this does not mean that it wasn’t prepared in advance for its use in present day humans. You could conjecture so, but it seems contrary to what we have discovered about the history of life. Do you have scientific evidence of any sort to support your conjecture?Zachriel_{December 24, 2014
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Hi AVS excuse me butting in, but: You wrote to Mung:
It makes much more sense that there was a common ancestor with a humerus, radius, ulna, etc. whose descendants kept this skeletal plan and went through small changes over the course of evolution to suit the varying selection pressures.
My comments: The human forelimb is the most general example of the pentadactyl limb found in vertebrates. It has no niche because it is capable of a multitude of functions. On the other hand we find versions of the pentadactyl limb which are specialised to varying degrees. And the more specialised it is the less likely it will allow its owner to progress beyond its observed niche. So, rather than the human forelimb being at the end of a blind process of change, the evidence points to it being the reverse. All other vertebrate limbs have taken the general human type plan and narrowed its function down to suit their specialised function. Getting back to my "parts are a reflection of the whole" from #49; as an embryo develops, structures and organs emerge in advance of the function/s that they have in the fully formed organism. Likewise the pentadactyl limb appeared in advance of the appearance of humans. But this does not mean that it wasn't prepared in advance for its use in present day humans. And also:
I’m simply asking why dolphins and whales have this huge brain that they must supply with oxygen despite living in an oxygen poor environment; meanwhile sharks are doing just fine in the same environment with a small brain and gills (the more suitable organ for gas exchange in an animal that spends its entire life in the water
Isn't that a question you should be asking a believer in the current paradigm? How have dolphins and whales managed to survive in an environment that their respiratory system makes them so poorly adapted to? Are you saying that they have thrived in their environment despite their respiratory systems? So we may look at an animal and say that it is successful in the survival race because of a certain feature but, on the other hand, it may be successful despite a certain feature. This tells us everything and nothing.CharlieM_{December 24, 2014
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CharlieM, I like to think so. Hopefully you will keep posting. It's not always easy for a holist to feel quite at home here at UD. However, one can reach the conclusion that arguing for information and organization (irreducible complexity) is in full accord with holism, since these concepts can be regarded as stemming from a holistic view. However, it is holism constrained by the empirical demands of science. The problem for our position is that the wholeness of things is not directly measurable.Box_{December 24, 2014
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Hi Box, I'm glad you enjoyed my post. From reading other threads I think we have a somewhat similar outlook.CharlieM_{December 24, 2014
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Like I already said Mungy, we do know what makes an organism what it is: it's genome and the differential gene expression of that genome. You're starting to not make sense though, try to stay here on Earth. As I said, you expect us to believe that the vertebrate limb skeleton evolved thousands of times with no change in the overall structure to suit very many different needs? No. It makes much more sense that there was a common ancestor with a humerus, radius, ulna, etc. whose descendants kept this skeletal plan and went through small changes over the course of evolution to suit the varying selection pressures. And don't put words in my mouth, I certainly did not say that they evolved from mammals with smaller brains, nor did I say that larger brains always evolved from smaller brains. Overall, mammals have a much larger cerebrum than other animals of comparable size, the dolphins and whales have retained this size increase. I'm simply asking why dolphins and whales have this huge brain that they must supply with oxygen despite living in an oxygen poor environment; meanwhile sharks are doing just fine in the same environment with a small brain and gills (the more suitable organ for gas exchange in an animal that spends its entire life in the water).AVS_{December 23, 2014
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AVS:
The large brains of dolphins and whales can’t be due to the evolution of these species from ancestral mammals could it?
You mean they evolved from mammals with smaller brains? So larger brains always evolve from smaller brains?Mung_{December 23, 2014
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AVS:
So lifepsy, you’d have us believe that the vertebrate limb evolved many different times, with virtually the same skeletal plan each time, in order to function in many very different ways? Wouldn’t it make more sense that vertebrates evolved from a common ancestor, retained the same skeletal limb plan, and these limbs adapted different functions?
Why would it "make more sense"?Mung_{December 23, 2014
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AVS:
We don’t know what makes an organism what it is? What does that even mean?
It means, my dear AVS, that to say that X is an instance of Y is to make a metaphysical claim.Mung_{December 23, 2014
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Yes, Joe, what are your thoughts on why dolphins and whales have such large brains in comparison to body size? Why not just increase gill size so as to have a larger surface area for gas exchange? Sharks seem to be doing just fine with their small brains and large gills. The large brains of dolphins and whales can't be due to the evolution of these species from ancestral mammals could it? Noooo, of course not. That would just make too much sense.AVS_{December 23, 2014
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CharlyM #49, Thank you for your thoughts. I especially enjoyed the part on the "rise of bipedalism".Box_{December 23, 2014
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So lifepsy, you'd have us believe that the vertebrate limb evolved many different times, with virtually the same skeletal plan each time, in order to function in many very different ways? Wouldn't it make more sense that vertebrates evolved from a common ancestor, retained the same skeletal limb plan, and these limbs adapted different functions? Many branches of the tree of life fit quite well together, showing gradual adaptations when you go with the second one. But if you'd like to continue ignoring the evidence then go right ahead.AVS_{December 23, 2014
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Zachriel, It’s not circular because the overall nested hierarchy remains with convergence being the exception. Alleged convergence can't even be identified until you demonstrate homology as a reference point. Homology is based on the assumption of the absence of convergence. “It is incredible that the descendants of two organisms, which had originally differed in a marked manner, should ever afterwards converge so closely as to lead to a near approach to identity throughout their whole organisation.” — Darwin Religious darwinian mysticism.lifepsy_{December 23, 2014
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AVS Similar structure/function relationships are used to infer relation, lifepsy? Yes... what do you think homology is? Homology is based on the fundamental assumption that a certain amount of complexity can not have multiple independent origins. This is the flimsy, undemonstrated basis supporting all of phylogenetics.lifepsy_{December 23, 2014
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I think that we need to get away from the gene centred, reductionist view of evolution before we can make any further progress in understanding life and evolution. The following are some observations that I believe fit the facts better than the current materialistic teaching on evolution. This is my personal opinion and just because I believe it to be close to the truth I don't expect every other person to do likewise. I have a holistic view in which I regard all of earthly life as a unity. The various forms are an individualised expression of that unity and individual, multicellular organisms are each a unified entity within the unified whole of life. When we regard the unity of an individual we must think of it as a unity in time as well as space. For example when we think of a rose we usually bring up a mental image of the flower, stem and a few leaves, perhaps even in a vase, but this is not the rose in its essence. That would be analogous to the 1812 Overture consisting only of a few canon shots. A rose, as a unified whole, is a dynamic entity which includes a progression from seed to mature plant. Earthly life is a unified whole from its origin to the appearance of self awareness in the human being. Everything is a building up towards the manifestation of self awareness in the form of the human. As physical life proceeds towards this end it is built from the base up on forms which remain at an earlier stage of development just as the individual human body must retain basal cells as its form develops. The bi-lateral form is on a direct line leading to self aware forms of life, the radial form is a side branch. The following transition can be used to describe the progression of life as a whole and also the progression of the human individual: From single cell, through water dwelling, tetrapod form, petadactyl limb, air breathing, from quadrupedalism to bipedalism, able to express its inward feelings by emitting sound, and finally producing the capability of rational thought and communicating these thoughts to others. The parts are a reflection of the whole. Now as our individual organs don't spring into existence by chance out of nothing, so the individual animal forms do not spring into existence by some random, undirected process. The animal forms are individualised expressions of the overarching type. The feline nature exists over and above the individual cat and it is this which determines the form of its body, how its limbs are shaped, how its teeth and claws take on the form that they do. The genes are not the cause of the form, they are only the means by which the physical form is able to be expressed. Many marsupials exhibit surprising similarity to their placental cousins. Due to their very similar natures they express the type in a similar way. The individual organism can be seen with the eye, the type cannot. But it can be seen. By using the mind as a sense organ the type can be observed. Invoking convergent evolution explains nothing. Take a look at the rise of bipedalism. We can say it is a demonstration of convergent evolution. What then? This explanation provokes no further though on the matter. But if we study the rise of bipedalism and think of it as a progression towards being able to use the limbs in a creative way, we can see a pattern. We humans have freed our forelimbs from the task of providing us with a means of locomotion and in so doing they become available for a much more creative use. Ever since land animals emerged from the water we see the striving for bipedalism in their forms. We see a hint of it by observing the difference between newts and frogs. Reptiles normally scuttle about on all four limbs or even none at all, but in some cases we see the beginning of bipedal motion. Look at dinosaurs, they attain bipedalism in creatures such as theropods, but in so doing their forelimbs become stunted. Each stage takes bipedalism to a new level and in birds we see the most advanced form of this arrangement. But birds have overshot the mark so to speak. They haven't actually freed their forelimbs for a higher purpose they still use them for locomotion; and in those that have lost the ability to fly, as in the ratites, their wings degenerate. Because we humans have freed our forelimbs from the task of support and locomotion we can use them to create the human made wonders we see all around us. Those are a few of my thoughts.CharlieM_{December 23, 2014
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Yes, AVS, design requirements. Obviously you have never studied design nor been part of a team who had to have different equipment play together without human interference.
You’d think the ability to take in oxygen while underwater would be a design requirement for an animal that lives its entire life in the water such as the dolphin, but we don’t see that do we?
Not enough O2 underwater to support their large brain. The design of the dolphin requires more O2 than is available underwater. Anything else I can help you with?Joe_{December 23, 2014
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Design requirements huh Joe? You'd think the ability to take in oxygen while underwater would be a design requirement for an animal that lives its entire life in the water such as the dolphin, but we don't see that do we? You're just making things up now Joe, talking out of a hole that isn't your mouth.AVS_{December 23, 2014
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AVS:
Then why are the dolphin, ichthyosaurus, blue marlin, and penguin scattered throughout the vertebrate tree?
Because those organisms, while similar due to a common design, are also different due to different design requirements.
What about birds and bats?
The differences outweigh the similarities.
The structural similarities in distantly related species are adaptations to similar selective forces and are defined as convergent evolution.
That's the propaganda anyway.Joe_{December 23, 2014
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Similar structure/function relationships are used to infer relation, lifepsy? Then why are the dolphin, ichthyosaurus, blue marlin, and penguin scattered throughout the vertebrate tree? What about birds and bats? If structure/function relationships were used to define lineages, wouldn't science say these species are closely related? But it doesn't . Why? Because relationships are not inferred by simply looking at overall body plan structure and functions like it seems you are saying. Instead, as I already said, evolutionary relationships are constructed based on fossil data, genome analysis, etc. The structural similarities in distantly related species are adaptations to similar selective forces and are defined as convergent evolution.AVS_{December 23, 2014
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Gradual evolution does NOT predict an objective nested hierarchy and there isn't one to be had wrt prokaryotes. Zachriel is obviously proud to lie for evolutionism.Joe_{December 23, 2014
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lifepsy: interesting circular reasoning It's not circular because the overall nested hierarchy remains with convergence being the exception. "It is incredible that the descendants of two organisms, which had originally differed in a marked manner, should ever afterwards converge so closely as to lead to a near approach to identity throughout their whole organisation." — DarwinZachriel_{December 23, 2014
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AVS, By combining evidence from fossils, genomic analysis, etc.... Actually that is a great way to objectively determine how distinct and separate different types of life really are. in order to put together estimates of lineages. "estimates of lineage" also known as darwinian imagineering.lifepsy_{December 23, 2014
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AVS, If two organisms demonstrate similar structure/function relationships and these organisms are not closely related, then it is an example of convergent evolution. What kind of objective check would you be looking for? interesting circular reasoning, AVS... similar structure/function relationships are the very criteria used to infer relation in the first place. the entire basis of homology is the assumption that the traits in question can not have an multiple independent origins. it is a weak inference based on the assumption that universal common descent must be true.lifepsy_{December 23, 2014
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We don't know what makes an organism what it is? What does that even mean? It's just another favorite nonsensical argument of creationists. If you want me to sum it up as simply as possible, we do know: different organisms have different genes and these genes undergo differential gene expression.AVS_{December 22, 2014
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Thank you Mung. I musta forgotten those rules.Joe_{December 22, 2014
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If we don't know what makes an organism what it is your evidence is subjective at best.Joe_{December 22, 2014
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