Dawkins: The Greatest Show on Earth
Dawkins: The Greatest Show on Earth – How Does Richard Dawkins deal with the Cambrian explosion?
To Dawkins’ credit in The Greatest Show on Earth, he does provide a reasonably detailed commentary on the geological incident known as the “Cambrian Explosion” (a phenomenon which is curiously omitted in many popular Darwinian texts) in his chapter on “The Missing Link? – What do you mean, ‘missing’?”. Richard Dawkins makes reference to the famous flatworms known as the Platyhelminthes:
This great phylum of worms includes the parasitic flukes and tapeworms, which are of great medical importance. My favourites, however, are the free-living tubellarian worms, of which there are more than four thousand species; that’s about as numerous as all the mammal species put together…They are common, both in water and on land, and presumably have been common for a very long time. You’d expect, therefore, to see a rich fossil history. Unfortunately, there is almost nothing. Apart from a handful of ambiguous trace fossils, not a single fossil flatworm has ever been found. The Platyhelminthes, to a worm, are ‘already in an advanced state of evolution, the very first time they appear. It is as though they were just planted there, without any evolutionary history.’ But in this case, ‘the very first time they appear’ is not the Cambrian but today. Do you see what this means, or at least ought to mean for creationists? Creationists believe that flatworms were created in the same week as all other creatures. They have therefore had exactly the same time in which to fossilise as all other animals. During all the centuries when all those bony or shelly animals were depositing happily alongside them, but without leaving any significant trace of their presence in the rocks. What, then, is so special about gaps in the record of these animals that do fossilise, given that the past history of the flatworms amounts to one big gap: even though the flatworms, by the creationists’ own account, have been living for the same length of time? If the gap before the Cambrian Explosion is used as evidence that most animals suddenly sprang into existence in the Cambrian, exactly the same ‘logic’ should be used to prove that the flatworms sprang into existence yesterday. Yet this contradicts the creationist’s belief that flatworms were created during the same creative week as everything else. You cannot have it both ways. This argument, at a stroke, completely destroys the creationist case that the Precambrian gap in the fossil record weakens the evidence for evolution.
Leaving that point aside, let us turn to Richard Dawkins’ understanding of the Cambrian explosion. First, even if we were to grant him his premise -- namely, the contention that organisms prior to the Cambrian were of a non-fossilisable composition (which is plausible) -- this is not the point in question. Indeed, it is to be expected that non-skeletonized predecessors ought to leave few if any fossils. If it were the case, therefore, that one evolving line appeared suddenly in the fossil record, once it reached the stage of being fossilizable, then Dawkins might have a point here. But the real challenge of the Cambrian explosion is the wide variety of fossilizable forms which appeared at more or less the same instant in geological time. Every single phyla represented by modern day organisms -- certainly all those with fossilizable parts -- were included, yet for none is there any clearly identifiable ancestor. It is explaining the simultaneous and abrupt appearance of those which is one of the leading challenges in evolutionary biology.
Dawkins’ argument here is by no means original. Interestingly, over the last century and a half since the publication of Darwin’s Origin of Species, paleontologists have discovered many Precambrian fossils, many of them microscopic or soft-bodied. As Darwinian paleobiologist William Schopf wrote in his The early evolution of life: solution to Darwin’s dilemma, “The long-held notion that Precambrian organisms must have been too small or too delicate to have been preserved in geological materials…[is] now recognised as incorrect.” If anything, the abrupt appearance of the major animal phyla, conventionally dated to about 540 million years ago, is better documented now that in Darwin’s time. Indeed, as more fossils are discovered it becomes clear that the Cambrian explosion was even more abrupt and extensive than previously envisioned.
Finally, the critic of Darwinism need not point to the fossil record as the most compelling decisive blow to Darwinian orthodoxy. Dawkins is free to invoke ad-hoc hypothesis in an attempt to explain away the gaps and challenges presented by the fossil record at the most crucial points. Nonetheless, the fact remains that the fossil record simply cannot be used to document anything relating to the common descent of all life forms -- which is one of the two central claims of neo-Darwinism. To state otherwise is to engage in circular reasoning.
Dawkins: The Greatest Show on Earth – Exaggerations and overstatements
Richard Dawkins' The Greatest Show on Earth, explains in great detail how evolution has occurred “before our very eyes”. He makes reference to the replication of the well-known bacterium E. coli as a means by which we can simulate ‘deep time’. He notes that while lizards experience a generation turnover period of about two years, bacterial generations are measured in hours, or even minutes. He points to Michigan professor Richard Lenski’s experiment where 12 identical lines of E. coli were cultured to over 44,000 generations (20 years later). The bacteria were grown in a medium which had a small amount of glucose (a primary carbon source for E. coli) and abundant citrate (a carbon source not normally utilised by E. coli). Every 500 generations, Lenski would take samples of the bacteria, which -- as Dawkins puts it -- in essence produced a ‘fossil record’ of the different tribes. Lenski observed many changes in the E. coli as they adapt to the culture conditions in his lab. While the fitness of bacteria had increased, it had come at a cost. For instance, all the tribes had lost the ability to catabolise ribose. Some tribes had lost the ability to repair DNA. These bacteria may indeed be more fit in a lab setting, but when placed back into their environment alongside their wild-type counterparts, they would be at a selective disadvantage.
Dawkins goes on to explain that at generation 31,500, one line of E. coli was found to be able to utilise citrate. Previous research in The Journal of Bacteriology has shown that wild-type E. coli can utilise citrate when oxygen levels are low. Under these conditions, citrate is taken into the cell and used in a fermentation pathway. The gene in E. coli is believed to encode a citrate transporter (a protein which transports citrate into the cell). In the presence of high levels of oxygen, it is believed that the citrate transporter does not function or is not produced, even while retaining the enzymes necessary for the utilisation of citrate. Thus, as it happens, wild-type E. coli already possesses the genes necessary for the transportation of citrate into the cell and subsequent utilisation of it.
So, what best explains the observations which Dawkins documents in The Greatest Show on Earth? As Lenski himself proposed in his 2008 paper in Proceedings of the National Academy of Sciences (105, no. 23), entitled: “Historical Contingency and the Evolution of a Key Innovation in an Experimental Population of Escherichia coli,” “A more likely possibility, in our view, is that an existing transporter has been co-opted for citrate transport under oxic [high oxygen levels] conditions.” He believes that this could be the same citrate transporter that is used in low oxygen conditions or indeed a transporter for another substrate that has been modified in order to transport citrate. The former would infer a loss of regulation, while the latter would imply a loss of specificity.
Dawkins: The Greatest Show on Earth – Does Richard Dawkins have the goods?
Richard Dawkins continues in the same vain throughout his book. One favourable review of Dawkins’ new book, published in The Guardian, commented that while The Greatest Show on Earth “demonstrates once again [Dawkins’] consummate skill as an explainer,” the science covered by the book mostly rehashed “pretty standard stuff.” The book fails to address the growing problems of biological information, the origin of life, how natural selection coupled with chance mutations can account for the origin of irreducibly complex systems, which continue to defy the Darwinism he preaches. Darwin called The Origin of Species ‘one long argument’ for his theory, but Richard Dawkins has given us one long bluff. The Greatest Show on Earth seeks to defend neo-Darwinism by appealing to theological arguments, by attempting to explain away the challenge of the Cambrian explosion by means of invoking ad-hoc conjectures, by exaggerating the evidence for the potentiality of natural selection, by misrepresenting design arguments, casting down ‘straw-men’, and by avoiding mention of the most sinister threats to the neo-Darwinian model of origins.
The actual evidence shows that major features of the fossil record and cell biology are an embarrassment to Darwinian evolution. Judged by the normal criteria of empirical science, the data used to prop up neo-Darwinism is weak. We know today that there are multiple critical facts which strike hard blows at the conventional understanding of the theory. These are not merely trivial problems or anomalies that are likely to be solved, but fundamental matters that appear to be without prospect of solution.
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