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Dollo’s Evolution Law gets hit again: Stripes come and go

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cichlids illustrate repeating (convergent) evolution/© Claudius Kratochwil

From ScienceDaily:

More than 1200 types of colourful cichlid can be found in the large African lakes Malawi, Victoria and Tanganjika. Not only are they very diverse in colours, they also have numerous colour patterns such as horizontal or vertical stripes. “But that’s not all” explains Axel Meyer, “cichlids are prime examples of evolution. They are extremely diverse in terms of social behaviour, body shape, colour pattern and many other biological aspects, but at the same time certain features repeatedly evolved independently in the different lakes.” This principle of repeated evolution — biologists term it convergent evolution — makes cichlids the perfect target to study the genetic basis of this phenomenon. If similar colours and body shapes have emerged in several evolutionary lines independently from each other this means that evolution reacted to similar environmental conditions in the same way. The question now is: When evolution repeats itself, how does this work genetically?

Convergent evolution implies underlying patterns rather than randomness. The researchers found a “stripe gene,” agrp2.

From an evolutionary point of view, the cichlids’ stripes are rather unstable. Over the course of a few million years, they have been lost and re-emerged in the African lakes many times over. As these species (with and without stripes) are so young, they can be interbred in aquaria. Breeding and examining the cichlids with and without stripes in the laboratory shows that all cichlids carry the “stripes gene,” but the switches (regulatory elements) of this gene differ. “This genetic switch causes the gene in species without stripes to be more activated. As a result, a lot of protein is produced. The “stripes gene” agrp2 works as a “stripes inhibitor”: if gene production is high, stripes will be suppressed, if production is low, they will remain. The researchers were able to demonstrate this by using modern genetic methods. “If we use CRISPR-Cas to remove the gene from the genome of a species without stripes,” Kratochwil explains, “then even a “stripeless” fish will suddenly develop stripes, as we showed with a CRISPR-Cas mutant fish. This proves that the stripes gene is the decisive genetic factor.”

The latest findings on this genetic mechanism, the activation or deactivation of stripes by the “stripes gene,” were published in the current issue of Science magazine. Interestingly, the cichlid’s agrp2 gene is a copy of the agouti gene in mammals, which is responsible for the different coat colours of cats, dogs, horses and striped baby birds. “The world of animals might be much less colourful without the agouti gene family,” reflects Claudius Kratochwil. The mechanism of the “stripes gene” in cichlids clearly makes repeated evolution possible within the briefest of times, relatively speaking. If characteristics are lost during evolution, usually this loss is forever, as the Belgian palaeontologist Louis Dollo already realized exactly 125 years ago, and wrote up his conclusions in “Dolls Law” in 1893. The special aspect of the stripes gene agrp2 is that it makes repeated evolution of a characteristic possible in a simple way. If a cichlid loses its stripes that does not mean they will never return or vice versa. These molecular-biological studies also show that palaeontological rules and evolutionary rules have to be questioned once again. Paper. (paywall) – Claudius F. Kratochwil, Yipeng Liang, Jan Gerwin, Joost M. Woltering, Sabine Urban, Frederico Henning, Gonzalo Machado-Schiaffino, C. Darrin Hulsey, Axel Meyer. Agouti-related peptide 2 facilitates convergent evolution of stripe patterns across cichlid fish radiations. Science, 2018 DOI: 10.1126/science.aao6809 More.

Notice the curious way the finding is described. Belgian palaeontologist Louis Dollo “realized” that if “ characteristics are lost during evolution, usually this loss is forever.” Yet the precise nature of this discovery is that Dollo is likely wrong. Kratochwil closes with “These molecular-biological studies also show that palaeontological rules and evolutionary rules have to be questioned once again.” Yes indeed, and we had best begin by identifying whether we are supporting or not supporting a given dogma.

What conceptual myths like Dollo’s Law mainly explain is this type of thing: “Museum director: Darwin’s theory of evolution not only underpins all biological science, it has an immense predictive power.” That is, increasingly, the only feature of the evolutionary landscape that Darwinian concepts shed light on is the behavior of the believers and enablers, the doubters and dissidents, and people who just can’t afford to lose their job.

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See also: Remember Dollo’s Law?: Once a trait was lost through evolution, it could not be regained.


Evolution appears to converge on goals—but in Darwinian terms, is that possible?

3 Replies to “Dollo’s Evolution Law gets hit again: Stripes come and go

  1. 1
    vmahuna says:

    “… the cichlids’ stripes are rather unstable. Over the course of a few million years, they have been lost and re-emerged in the African lakes many times over.”

    OK, ya wanna tell me HOW we know that something as ephemeral as STRIPES can be documented over a period of millions of years? I guess this MIGHT be possible through lots of detailed studies of the DNA from 2 million year old cichlid fossils, but come on: the guys know (guess?) the cichlids have lived in lakes in Africa for “a long time”. And so they’re ASSUMING that the stripes and colors have ALWAYS changed the way we’ve observed in modern cichlid populations over the hundred years or so. Does that even COUNT as Science? If 2 guys without degrees sit around drinking beer, are their comments on fish and fishing “science”?

  2. 2
    bornagain77 says:

    as to this comment from the article:

    “cichlids are prime examples of evolution. They are extremely diverse in terms of social behaviour, body shape, colour pattern and many other biological aspects, but at the same time certain features repeatedly evolved independently in the different lakes.” This principle of repeated evolution — biologists term it convergent evolution,,,

    First, cichlids certainly are NOT prime examples of evolution but are prime examples of the tremendous variety that is inherent in a distinct species. Much like the tremendous variety that is inherent within wolves that is then subsequently expressed in dogs.

    These following studies and video, on Cichlid fishes, are evidence of the ‘limited and rapid variation from a parent kind’ predicted by the Genetic Entropy model (John Sanford):

    African cichlid fish: a model system in adaptive radiation research:
    “The African cichlid fish radiations are the most diverse extant animal radiations and provide a unique system to test predictions of speciation and adaptive radiation theory(of evolution).—-(surprising implication of the study?)—- the propensity to radiate was significantly higher in lineages whose precursors emerged from more ancient adaptive radiations than in other lineages”

    Cichlid speciation attributed to “plasticity” – December 7, 2016
    Excerpt: There is increasing evidence that phenotypic plasticity can promote population divergence by facilitating phenotypic diversification and, eventually, genetic divergence. When a ‘plastic’ population colonizes a new habitat, it has the possibility to occupy multiple niches by expressing several distinct phenotypes. These initially reflect the population’s plastic range but may later become genetically fixed by selection via the process of ‘genetic assimilation’ (GA). Through this process multiple specialized sister lineages can arise that share a common plastic ancestor – the ‘flexible stem’,,,

    Real Time Evolution “Happening Under Our Nose” – October 12, 2015
    Excerpt: Our research shows that these fish adapted to their new habitats in less than one year, or three to four generations, which is even faster than we previously thought.,,,
    Lee Spetner commenting on Reznick’s earlier work:
    Reznick and his team took 200 guppies from the Aripo [river in Trinidad] and put them in a tributary of the river that is home to the killfish but has no cichlids and had no guppies. Changes soon appeared in the newly introduced guppies. The fish population soon changed to what would normally be found in the presence of the killfish, and Reznick found the changes to be heritable.
    The full change in the guppy population was observed as soon as the first samples were drawn, which was after only two years. One trait studied, the age of males at maturity, achieved its terminal value in only four years. The evolutionary rate calculated from this observation is some ten million times the rate of evolution induced from observations of the fossil record [Reznick et al. 1997].
    Reznick interpreted these changes as the result of natural selection acting on variation already in the population. Could natural selection have acted so fast as to change the entire population in only two years?

    Dr. Arthur Jones, who did his Ph.D. thesis in biology on cichlids, (fish), comments

    “For all the diversity of species, I found the cichlids to be an unmistakably natural group, a created kind. The more I worked with these fish the clearer my recognition of “cichlidness” became and the more distinct they seemed from all the “similar” fishes I studied. Conversations at conferences and literature searches confirmed that this was the common experience of experts in every area of systematic biology. Distinct kinds really are there and the experts know it to be so. – On a wider canvas, fossils provided no comfort to evolutionists. All fish, living and fossil, belong to distinct kinds; “links” are decidedly missing.”
    Dr. Arthur Jones – did his Ph.D. thesis in biology on cichlids – Fish, Fossils and Evolution – Cichlids at 29:00 minute mark (many examples of repeated morphology in cichlids) – video

    Second, ‘convergent evolution’ may be what evolutionists have named the repeated appearance of certain features, for example eyes, in completely different species, but just because they tacked the name ‘convergent evolution’ onto the repeated appearance of a certain features in completely different species , it certainly does not mean that Darwinists have given any kind of coherent explanation for why this repeated appearance of a feature should happen.

    The fact of the matter is that ‘convergent evolution’ is actually evidence against Darwinian evolution, not evidence for it.

    Problem 7: Convergent Evolution Challenges Darwinism and Destroys the Logic Behind Common Ancestry – Casey Luskin February 9, 2015
    Excerpt: 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,,,,
    Biochemist and Darwin-skeptic Fazale Rana reviewed the technical literature and documented over 100 reported cases of convergent genetic evolution.126 Each 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.,,,

    Darwinism Versus the Octopus: An Evolutionary Dilemma – Eric Metaxas – September 08, 2015
    Excerpt: What’s the difference between evolutionary theory and an octopus? Well, one is a slippery, color-changing escape artist that can get out of any tough situation and the other is an aquatic invertebrate.,,,
    The key to this uncanny intelligence is the octopus’ so-called “alien” nervous system, brain, and eyes. But these features are not alien to the animal kingdom at all. In fact, they’re quite common in higher vertebrates. The octopus genome shares key similarities with ours, including the development of high-powered brains and “camera eyes” with a cornea, lens, and retina.
    Now here’s the problem for evolution: according to Neo-Darwinists, we’re not related to octopi—at least not within the last several hundred million years. That means all of these genes, complex structures, and incredible capabilities came about twice.
    The researchers who sequenced the octopus genome call this “a striking example of convergent evolution,” or the supposed tendency of unrelated creatures to develop the same traits in response to environmental pressures. Isn’t that just a fancy way of saying a miracle happened twice?
    But the octopus isn’t the only such miracle. “Convergent evolution” is all over nature, from powered flight evolving three times to each continent having its own version of the anteater. Think about that. As one delightfully un-self-conscious “Science Today” cover put it, convergent evolution is “nature discover[ing] the same design over and over.” Well, good for nature!
    But as Luskin argues, there’s a better explanation for a tentacled mollusk having a mammal’s brain and human eyes. And that explanation is common design by an intelligent Engineer. And like all good engineers, this this one reused some of His best designs.
    Now that explanation isn’t going to satisfy Darwinian naturalists. And they’ll probably keep on invoking “convergent evolution” when faced with impossible coincidences in nature.
    But hopefully knowing a more straightforward explanation leaves you forearmed—or should I said “eight-armed”?

    The Real Problem With Convergence – Cornelius Hunter – May 25, 2017
    Excerpt: 21st century evolutionists are still befuddled by convergence, which is rampant in biology, and how it could occur. This certainly is a problem for the theory.,,,
    a fundamental evidence and prediction of evolution is falsified.
    The species do not fall into the expected evolutionary pattern.
    The failure of fundamental predictions — and this is a hard failure — is fatal for scientific theories. It leaves evolution not as a scientific theory but as an ad hoc exercise in storytelling.

    “The reason evolutionary biologists believe in “40 known independent eye evolutions” isn’t because they’ve reconstructed those evolutionary pathways, but because eyes don’t assume a treelike pattern on the famous Darwinian “tree of life.” Darwinists are accordingly forced, again and again, to invoke convergent “independent” evolution of eyes to explain why eyes are distributed in such a non-tree-like fashion.
    This is hardly evidence against ID. In fact the appearance of eyes within widely disparate groups speaks eloquently of common design. Eyes are a problem, all right — for Darwinism.”

    Simon Conway Morris has a website documenting hundreds, if not thousands, of examples of unexpected and unexplained ‘convergent evolution’:

    Map Of Life – Simon Conway Morris

    Of related note:

    “Whatever we may try to do within a given species, we soon reach limits which we cannot break through. A wall exists on every side of each species. That wall is the DNA coding, which permits wide variety within it (within the gene pool, or the genotype of a species)-but no exit through that wall. Darwin’s gradualism is bounded by internal constraints, beyond which selection is useless.”
    R. Milner, Encyclopedia of Evolution (1990)

    Excerpt: There are limitations to variability. “The real number of variations is lesser than expected one. There are no blue-eyed Drosophila, no viviparous birds or turtles, no hexapod mammals, etc. Such observations provoke non-Darwinian evolutionary concepts. Darwin tried rather unsuccessfully to solve the problem of the contradictions between his model of random variability and the existence of constraints. He tried to hide this complication citing abundant facts on other phenomena. The authors of the modern versions of Darwinism followed this strategy, allowing the question to persist. …However, he was forced to admit some cases where creating anything humans may wish for was impossible. For example, when the English farmers decided to get cows with thick hams, they soon abandoned this attempt since they perished too frequently during delivery. Evidently such cases provoked an idea on the limitations to variability… The problem of the constraints on variation was not solved neither within the framework of the proper Darwin’s theory, nor within the framework of modern Darwinism.”
    – per pdf document

  3. 3
    aarceng says:

    Are the cichlids different species or just different varieties within one species? Since they can interbreed in aquariums I would favour the latter.

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