Any good biologist worth his or her salt (or should I say calcium carbonate?).....and yes I am a biologist, will tell you that this controversial theory, and that is exactly what it is, speculative conjecturing, is far from settled.
Strata of Cambrian rock were first studied in Wales by British biologist Adam Sedgewick (1785-1873), who named the period for ancient Wales (Lat.Cambria). Geologists in many areas of the world employ a variety of classification systems some characterized by the presence or absence of trilobites. Cambrian rocks are found in Europe, North America, Newfoundland, eastern Canada, various countries of South America and Asia. As far as my personal research can determine all Cambrian fossils found thus far were saltwater dwellers; the plant dwellers of the period are seaweeds, and the animal fossils are invertebrates. The Cambrian Period is also known as Biology’s Big Bang and the Cambrian Explosion because of its great diversity of life.
Even Charles Darwin, a Christian scientist, was skeptical about the Cambrian Explosion hypothesis. The idea was attractive to the Church as The Deity of Evolution. A great way to explain the sudden appearance of life without the evidence of interim fossils...that evolution was a sudden burst of activity with ensuing periods of little change. So we now had a reasonable speculation for the sudden appearance of life (supported by numerous fossils) in the Cambrian Period, implying that the Cambrian was a pulse of rapid evolution. Darwin believed more along the lines that evolution progressed at a more even pace and it was only a matter of finding fossils under the Cambrian strata.
'I cannot doubt that all the Silurian trilobites have descended from some one crustacean, which must have lived long before the Silurian age....Consequently, if my theory be true, it is indisputable that before the lowest Silurian strata was deposited, long periods elapsed, as long as, or probably longer than, the whole interval from the Silurian to the present day.....The case must at present remain inexplicable; and may be truly urged as a valid argument against the views here entertained'...... it is indisputable that before the lowest Silurian stratum was deposited, long periods elapsed, as long as, or probably far longer than, the whole interval from the Silurian age to the present day; and that during these vast, yet quite unknown periods of time, the world swarmed with living creatures. To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer. 1
The Origin of Species, 1859, pp. 313 - 314.
Time ran out and Darwin was unable to find this strata leaving the Church only able to assert that that life appeared at one moment: in the Cambrian Explosion created by God. Today along with science and technology, scientists are still speculating about the evidence of Darwin’s hypotheses. Fossils under the Cambrian strata, known as the Vendian or Ediacaran suggest that multicellular life existed even before the Cambrian Period and surely lends a lot of credibility to Darwin's ideas.
It bears repeating because rk2001 states it very clearly in her summarizing statement: "How the earth came to overflow with such a great number of animal species all of a sudden and how these distinct types of species with no common ancestors could have emerged is a question that remains unanswered by evolutionists..."
Encyclopedia references go on to say in part:
.....reasons for (the Cambrian Explosion) are still debated, but a leading theory is that the amount of oxygen in the atmosphere had finally reached levels that allowed large, complex animals to exist. Oxygen levels may also have facilitated the metabolic processes that produce collagen, a protein building block that is the basis for hard structures in the body.
A recent issue of Scientific American, Life Goes for a Spin
A topsy-turfy earth may have triggered an evolutionary big bang, tells an even more far reaching speculation that is garnering attention:
Scientists have advanced many theories to explain that big bang in the diversification of life, none of them fully convincing. Now Joseph L. Kirschvink of the California Institute of Technology and his colleagues believe they may have solved what he calls "one of the outstanding mysteries of the biosphere." Life on the earth turned upside down, Kirschvink proposes, because the earth itself turned upside down: an abnormally rapid reorganization of the earth's crust, tens of times faster than normal continental drift, touched off sharp climatic shifts that in turn unleashed a torrent of evolutionary change.
Kirschvink and his co-authors (Robert L. Ripperdan of the University of Puerto Rico and David A. Evans, also at Caltech) cite their body of principles offers to explain the phenomena by outlining various areas of evidence for a time period of great geological upheaval. They use Rodinia as a reference, a giant continental landmass torn apart and almost simultaneously put back together again as another supercontinent, Gondwana. Sudden changes in the oceans chemistry is recorded in sedimentary rocks. Using new uranium-lead dating techniques to lend credible proof they say that these changes all occurred rapidly and simultaneously with the Cambrian Explosion. Collected data appears to show that earth's continental crust (the entire surface of the earth) rotated 90 degrees in a geologically brief 15 million years. Kirschvink and his researchers suspect a mechanical phenomena called 'polar wander' was responsible producing a much faster movement that an average continental drift. These swift motions the writers ideate would have given the kick start to the early Cambrian life on the earth:
The repeated reorganizations in global wander during a true polar wander event should have fragmented any large-scale ecosystems that were established, generating smaller, more isolated populations and leading to a higher evolutionary branching rate among existing groups."
the researchers say with confidence in their postulation in the July 25, 1997, issue of Science.
Their hope is that their theory of polar wander will become an additional instrument in the understanding the geology and biology of the Cambrian Explosion. This analysis is however by no means meant to be considered as conclusive proof of the explanation of the Cambrian Explosion. All good scientists keep open minds and form objective opinions based on the current evidence. Like the other possible explanations presented here, such as physiological theories of fossilization and genetic studies gathered here can be added to the many other theories abounding such as the appearance of the first true carnivores and the role they may also have played.
Given all together these explanations are still only tools in man's feeble attempt to explain the nature of this indeed as rk2001, states so accurately a miraculous event, the explanation of which still remains beyond the visible and observable universe.
CAMBRIAN EXPLOSION / ORIGIN OF THE PHYLA:
The Cambrian Explosian:
1 In Darwin's time, the "Silurian" was the name given the oldest known fossil-bearing strata. "Cambrian" does not occur as an index entry in this edition of the Origin.