Friday, 10 January 2014

Elephant Sharks Living In The Past

The elephant or ghost shark, Callorhinchus milii
Elephant shark takes record for slowest evolution - life - 08 January 2014 - New Scientist.

Expecting a religious fundamentalist to do logic is like expecting a cow to do acrobatics. For example, I've been assured in all seriousness that the fact that coelacanths have 'not evolved' for 400 million years proves that evolution doesn't occur, so Earth is only 6000 years old just like the Bible says. Almost the same argument is made for the horseshoe crab.

The difference in this approach and that of science is due to the differences in motivation. The aim of science is to discover the ultimate truth, or at least to get as close to it as is possible. The aim of religious fundamentalists is to satisfy their yearning for a sense of self-importance which can only be satiated by believing that an assumed creator of the universe made it just for them and has a special relationship with them. Anything which can be used to support this is grasped eagerly like a drowning person clutches at straws. No logic will be allowed to spoil a good 'proof'.

So, orders like the coelacanths or or horseshoe crabs are 'proof' that evolution doesn't happen because they've remained unchanged for millions of years, whilst all the species which have not remained unchanged have no bearing on the matter, so a magic man must have made humans just the way they are.

Well, here's another species, the elephant shark, Callorhinchus milii, which hasn't changed very much since the order evolved some 400 million years ago. In fact, Byrappa Venkatesh of the Institute of Molecular and Cell Biology in Singapore, as reported in a paper published in Nature, has found that its genome has changed least over a similar time scale of any species to have its genome analysed so far. Despite its common name it is only distantly related to sharks in that it is a cartilaginous fish, like the sharks, skates and rays. In fact, it's a ratfish.

The emergence of jawed vertebrates (gnathostomes) from jawless vertebrates was accompanied by major morphological and physiological innovations, such as hinged jaws, paired fins and immunoglobulin-based adaptive immunity. Gnathostomes subsequently diverged into two groups, the cartilaginous fishes and the bony vertebrates. Here we report the whole-genome analysis of a cartilaginous fish, the elephant shark (Callorhinchus milii). We find that the C. milii genome is the slowest evolving of all known vertebrates, including the ‘living fossil’ coelacanth, and features extensive synteny conservation with tetrapod genomes, making it a good model for comparative analyses of gnathostome genomes. Our functional studies suggest that the lack of genes encoding secreted calcium-binding phosphoproteins in cartilaginous fishes explains the absence of bone in their endoskeleton. Furthermore, the adaptive immune system of cartilaginous fishes is unusual: it lacks the canonical CD4 co-receptor and most transcription factors, cytokines and cytokine receptors related to the CD4 lineage, despite the presence of polymorphic major histocompatibility complex class II molecules. It thus presents a new model for understanding the origin of adaptive immunity.


We're getting this divorce between the apparent conservatism of their genome and the astonishing singing and dancing that was going on anatomically.

Michael Coates, palaeontologist,
University of Chicago
The fact that its genome has changed far less than would normally be expected is surprising in another way because between about 300 and 340 million years ago the order underwent a rapid radiation from the ancestral species, which suggests rapid, not slow, evolution of the genome. For some reason as yet not fully understood, C. milii seems to have retained a genome close to the ancestral form whilst its relatives were rapidly changing and diversifying.

Note here another difference in the reaction of creationists and scientists. Scientists actually welcome something which throws a spanner in the works and causes us to question our basic assumptions. Nothing is more satisfying than publishing some data which challenges our assumptions. We freely admit we don't know the answer and equally freely admit it when something seems to go against what we think we know. There is no rigidly inflexible dogma to be defended at all costs. If it turns out we're wrong to some degree or other, we revise our understanding and change our conclusions. The facts, as always, are the master.

But that's not the only thing we see here. Because the elephant shark's genome is believed to be close to that of the common ancestor of not only the cartilaginous fish but that of the bony fish, and so, via amphibians and reptile of us, there is the possibility that we can learn a great deal about how things like our immune systems evolved because it evolved at some point during that initial radiation. Science seizes on the chance to extend our knowledge rather than treating an inconvenient fact as a problem not to be discussed in front of the children or to be hidden under the carpet.

By contrast, in their desperate search for confirmation of their own inflated self-importance, no matter how spurious or illogical, the last thing fundamentalist will acknowledge is the possibility of being wrong. On no account can the conclusion be changed because the conclusion comes from dogma not from facts. To even consider questioning the dogma is heretical. If the facts point elsewhere then the facts must be wrong. The only facts worth considering are those which seem to support the dogma, and they are then waved around triumphantly and science is acclaimed as incontrovertible proof.

So, the elephant shark, the coelacanth and the horseshoe crab are all 'proof' that evolution doesn't happen because they haven't evolved for hundreds of millions of years, therefore Earth is only 6000 years old. Remember, when you join those dots, the ones which don't make a god have been put there to mislead you!

The Discovery Institute and the Institute for Creation Research want this creation 'science' taught to our children in place of real science!

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3 comments :

  1. I just shared your article on twitter just to learn @RosaRessurected had been suspended. I'm sorry to learn that. You were a credit to twitter.

    My regards.

    ReplyDelete
  2. I don't think it's quite accurate to say the coelacanths haven't evolved. Fossil coelacanths are much smaller. Also, there are two distinct populations of coelacanth - one off the Comoros and the other in Indonesia - which are distinct in appearance (though of the same size) and belong to different species. This proves without doubt that they have evolved further after the fossil record ended.

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  3. Absolutely, but then creationists aren't bothered by little niceties such as truth and accuracy. They read that coelacanths were believe to have gone extinct in the Late Cretaceous until one was found in 1938 and dubbed a 'living fossil', so they proclaim that it hasn't evolved, just so with the horseshoe crabs, of which there are four species which have evolved from a common ancestor in the last few million years. The fact that they are the only members of an ancient order is good enough for creationists to declare that they haven't evolved and then to use that 'fact' to spread disinformation and misunderstanding amongst their ignorant followers.

    See Religion's Living Fossils.

    ReplyDelete

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