The Cambrian explosion refers to the sudden appearance of new body plans in the fossil record. ID proponents think that the period is between 5-10 million years at the most. Naturalists want to stretch out the period in which the body plans appear to tens of millions of years. The two sides can’t both be right. What’s the truth?
Evolution News has the answer.
To establish the length of the most explosive period of innovation within the Cambrian explosion itself, Meyer cites the work of MIT geochronologist Samuel Bowring and his colleagues as well the work of another group led by Smithsonian paleontologist Douglas Erwin. The Bowring-led study showed that (in their words) “the main period of exponential diversification” within the Cambrian lasted “only 5-6 million years” (emphasis added). Meyer explains:
An analysis by MIT geochronologist Samuel Bowring has shown that the main pulse of Cambrian morphological innovation occurred in a sedimentary sequence spanning no more than 6 million years. Yet during this time representatives of at least sixteen completely novel phyla and about thirty classes first appeared in the rock record. In a more recent paper using a slightly different dating scheme, Douglas Erwin and colleagues similarly show that thirteen new phyla appear in a roughly 6-million-year window. (p. 73)
[...][T]ake a look first at the following figure that Bowring and his colleagues included in their definitive 1993 article, published in the journal Science. They use radiometric methods to date the different stages of the Cambrian period, including the crucial Tommotian and Atdabanian stages in which the greatest number of new animal phyla and classes arise. Note that the so-called Manykaian stage of the Cambrian period lasts about 10-14 million years. Note also that the main pulse of morphological innovation didn’t begin during this stage but rather during the Tommotian and Atdabanian — a period that they describe as taking between “5 to 10 million years,” and in a more detailed passage as taking about 5-6 million years.
[...]In the figure above, the Tommotian and Atdabanian stages of the Cambrian period together span only about 5 million years, starting at about 530 and ending about 525 million years ago. Bowring’s figure also depicts the total number of classes and orders present at any given time during the Cambrian period. The biggest increases in morphological innovation occur during the Tommotian and Atdabanian stages. Indeed, during this period the number of known orders nearly quadruples. Moreover, Bowring and his colleagues also make clear that this period corresponds to the main pulse of Cambrian morphological innovation as measured by the number of new phyla and classes that first appear. They note that, while a few groups of animals do arise in the earliest Manykaian stage of the Cambrian, the most rapid period of “exponential increase of diversification,” corresponding to the Tommotian and Atdabanian stages, “lasted only 5 to 6 m.y.”
You can see the figure they are reference in the Evolution News article.
Also, check out these clips that explain the Cambrian explosion:
The first clip features James Valentine, a professor of biology at the University of California who just co-authored a new book on the Cambrian explosion and is not a proponent of intelligent design.
The consensus among scientists regarding the period of time in which the new body plans appear is 5-6 million years. Biologically speaking, that’s a blink of an eye. You aren’t going that kind of complexity and innovation in such a short period of time any more than you can expect to win the lottery by buying 5-6 million tickets when the odds of winning are 1 in a googol (10 to the 100th power – 1, followed by 100 zeroes). You don’t have enough lottery tickets to make winning the lottery likely. Similarly, 5-6 million years is not enough time for naturalistic mechanisms to code brand new body plans from scratch. It would be like trying to research and write a Ph.D thesis during a single lunch hour. It’s just not enough time to produce the amount of information that’s required.