Science, Creation & EvolutionSudden appearance of phyla in the Cambrian explosionThis is an excellent question and one that has intrigued scientists for a long time. Before I give you my answer, could you tell me what sort of evidence you would accept as reasonable? I would also like to say that the Cambrian radiation is a hotly debated issue in science because there is so much we don't know about it. Recent work has hinted at some points of discussion and the evolutionary perspective on the CE has generated some predictions borne out by later studies. However, at this point in time, no one can answer your question about the detailed evolutionary steps leading to the Cambrian fossil record. So, if the answer that satisfies you is that "We don't know" then you can stop reading this thread. If you'd like to know what we do know and what paths of research are active, please read on. Last year (2004) 3 articles came out independently and in rapid succession detailing the Cambrian explosion. The first of these articles dealt with the paleogeographical distribution of the trilobites and the implications of the paleogeography on their evolutionary history. Let me summarize briefly. The paper suggested that the lineage of trilobites were rooted in a bilaterian ancestor that should be found in strata dating back some 50-80 million years (i.e. 570-600 Myr) before their appearance in the fossil record (~520 Myr Note: At the time the paper was published fossil evidence for the bilaterian body plan were not well known). At nearly the same time, a second paper was published on predation in trilobites. This was an important finding because it suggested that an ecosystem (complete with predatory behavior) had developed prior to the appearance of trilobites in the fossil record. The roughly two months after these articles were published a third paper came out describing the discovery of bilaterian fossils in strata dating to ~580 Myr precisely as predicted by the first paper (web links to these discoveries are listed below). To summarize, all science is incomplete, but an incomplete record does not mean we are on the wrong path towards solving the problem. As I've noted before, we must choose the methods that are likely to bear the most fruit and evolutionary biology is 'the unifying principle of biology'. To the best of my knowledge, there is no other explanation for the CE other than evolution (if I am wrong, please let me know what that explanation might be). -E Web Links: http://dsc.discovery.com/news/briefs/20 ... nimal.html http://english.people.com.cn/200406/06/ ... 45457.html |
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