Sean B. Carroll Trots Out the Same Old Tired Defense Against the Cambrian Challenge to Darwinism - Evolution News & Views

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Sean B. Carroll Trots Out the Same Old Tired Defense Against the Cambrian Challenge to Darwinism

An article appeared in The New York Times last week written by the popular geneticist, Sean B. Carroll, who is probably best known for his professional and popular work on the emerging science of evo devo. Carroll's article attempts to refute the challenges posed by the Cambrian fossil record to evolutionary thought. Carroll writes,

The difficulty posed by the Cambrian Explosion was that in Darwin's day (and for many years after), no fossils were known in the enormous, older rock formations below those of the Cambrian. This was an extremely unsettling fact for his theory of evolution because complex animals should have been preceded in the fossil record by simpler forms.

In "On the Origin of Species," Darwin posited that "during these vast, yet quite unknown, periods of time, the world swarmed with living creatures." But he admitted candidly, "To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer."

Although a major dilemma at the time of Darwin's writing of The Origin, the problem posed to evolutionary thought by the Cambrian in modern times is not an absence of fossils in the Precambrian strata. Rather, it is the absence of fossil precursors to the highly diverse phyla found in the Cambrian.. One would think that Carroll, an expert in this area, would have considered this conundrum. However, Carroll attempts to rebut this problem by attacking a straw man. He continues,

It took a very long time, and the searching of some of the most remote places on the planet -- in the Australian Outback, the Namibian desert, the shores of Newfoundland and far northern Russia -- but we now have fossil records from the time immediately preceding the Cambrian. The rocks reveal a world whose oceans were teeming with a variety of life forms, including primitive animals, which is certainly good news for Darwin.

Now, this once-worrisome gap in the fossil record is a period of intense interest to geologists as well as paleontologists. The former have even given it its own division in the geological timescale. The Ediacaran Period, from 635 to 542 million years ago, is the first new geological period to be named in more than a century. Moreover, geologists have developed some intriguing theories about how dramatic changes in the Earth's climate and chemistry during the Ediacaran may have allowed for the evolution of animals.

Carroll goes on to discuss the discovery of the fossil remains of Precambrian soft-bodied creatures such as the Cnidaria by the geologist Reginald Sprigg in 1946. Carroll explains,
Scientific attention to these strange forms was not revived until a decade later when more soft-bodied forms were found in the Ediacaran Hills and in England, and their age was firmly established as actually predating the Cambrian. Deposits of similar aged forms have been discovered at Mistaken Point on the Avalon Peninsula of Newfoundland, in southern Namibia, the White Sea of Russia, and more than 30 other locations on five continents. The global distribution of these disc-, frond-, tube-, branch-, or spindle-shaped forms demonstrate that life was complex and diverse in the Ediacaran.
What does Carroll conclude about the Ediacaran fauna?
The Ediacaran fossil record thus stretches the origins of animals to well before the Cambrian Explosion. But it also raises the question of why, after more than 2.5 billion years during which microscopic life dominated the planet, larger, more complex, forms emerged at that time?
I, for one, am at a loss as to why Carroll and his fellow evolutionary theorizers find this sort of argumentation to be a convincing rebuttal to the Cambrian challenge to Darwin's theory. Far from resolving Darwin's dilemma, the presence of precambrian softbodied organisms -- particularly the sponge embryos -- only serves to deepen it and make the problem far worse. Darwinists want to have it both ways: "The conditions of the Cambrian were not suitable for the preservation of softbodied organisms so we shouldn't expect to see the immediate precursors to the Cambrian fauna. Oh, and by the way, did we mention that the Cambrian wasn't really an explosion at all because we have found soft bodied organisms in the Ediacaran assemblages, including the Cnidaria and even sponge embryos?"

At any rate, as discussed in some detail here, the Ediacaran fauna are not broadly thought to be the ancestors of modern taxonomic groups such as the various metazoan phyla which appear explosively in the Cambrian radiation. The presence of these organisms, therefore, should offer no comfort to Darwinists. As Peter Ward has observed in On Methuselah's Trail: Living Fossils and the Great Extinctions, "[L]ater study cast doubt on the affinity between these ancient remains preserved in sandstones and living creatures of today; the great German paleontologist A. Seilacher, of Tübingen University, has even gone so far as to suggest that the Ediacaran fauna has no relationship whatsoever with any currently living creatures. In this view, the Ediacaran fauna was completely annihilated before the start of the Cambrian fauna." (p. 36)