Wrapping up the Cambrian explosion in a bow-tied package and putting it away in the closet … or maybe not?
|May 5, 2012||Posted by News under Cambrian explosion, News|
In “In Explaining the Cambrian Explosion, Has the TalkOrigins Archive Resolved Darwin’s Dilemma?” (Evolution News & Views, May 2, 2012)- regarding the Cambrian explosion – Jonathan M. offers,
A correspondent recently referred me to an article in the TalkOrigins Archive responding to the argument that “Complex life forms appear suddenly in the Cambrian explosion, with no ancestral fossils.” TalkOrigins is a popular online resource that collects attempted answers to some often-heard challenges to Darwinian evolutionary theory. The article offers seven responses to the contention that the Cambrian explosion, which occurred some 530 million years ago, represents a significant difficulty for the neo-Darwinian view on how animal body plans evolved.
Since this subject comes up frequently in the evolution debate, as indeed the seeming dilemma posed by the Cambrian event troubled Darwin himself, I here offer a brief reply to TalkOrigins.
Response #1: Complex life preceded the Cambrian.
The article explains,
The Cambrian explosion was the seemingly sudden appearance of a variety of complex animals about 540 million years ago (Mya), but it was not the origin of complex life. Evidence of multicellular life from about 590 and 560 Mya appears in the Doushantuo Formation in China (Chen et al. 2000, 2004), and diverse fossil forms occurred before 555 Mya (Martin et al. 2000). (The Cambrian began 543 Mya., and the Cambrian explosion is considered by many to start with the first trilobites, about 530 Mya.) Testate amoebae are known from about 750 Mya (Porter and Knoll 2000). There are tracelike fossils more than 1,200 Mya in the Stirling Range Formation of Australia (Rasmussen et al. 2002). Eukaryotes (which have relatively complex cells) may have arisen 2,700 Mya, according to fossil chemical evidence (Brocks et al. 1999). Stromatolites show evidence of microbial life 3,430 Mya (Allwood et al. 2006). Fossil microorganisms may have been found from 3,465 Mya (Schopf 1993). There is isotopic evidence of sulfur-reducing bacteria from 3,470 Mya (Shen et al. 2001) and possible evidence of microbial etching of volcanic glass from 3,480 Mya (Furnes et al. 2004).
None of this is news to us. As the article correctly notes, there is evidence of multicellular life in the Doushantuo formation in China, dating to a few tens of millions of years prior to the Cambrian. Vernanimalcula guizhouena, for example, which is the earliest known Bilateria, is found in deposits dating from 600 to 580 million years ago. The Doushantuo formation also contains fossilized microscopic sponges and corals and various other aquatic microscopic fauna.
Far from resolving Darwin’s dilemma, however, the discovery of these small and fragile organisms has only accentuated the problem, for it substantially undermines the common response that the Precambrian organisms were too small and too soft-bodied to be preserved. The same is true with respect to the testate (shelled) amoebae fossils that date back to the Cryogenian period (850-635 million years ago). None of the organisms mentioned by TalkOrigins represent transitional precursors to the forms that appear so abruptly during the Cambrian explosion.
The difficulty with “explaining the Cambrian explosion” efforts is that the explainers are not trying to explain it. They are trying to explain it away. That is a very different procedure.
Explaining an event includes, at minimum, offering a credible account, whether or not it supports Darwinism. Whereas what we really hear from explainers away is a non-credible account that satisfies the emotional needs of the people with a vested interest in avoiding the difficulty that the attested event presents to Darwinism.
As more is learned about the Cambrian, distortions fronted in the education system are likely to grow in number and depth.