Development. 1999 Feb;126(5):851-9.
Fossils, molecules and embryos: new perspectives on the Cambrian explosion.
Valentine JW, Jablonski D, Erwin DH.
Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA 94720, USA. firstname.lastname@example.org
The Cambrian explosion is named for the geologically sudden appearance of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals. Earlier indications of metazoans are found in the Neoproterozic; minute trails suggesting bilaterian activity date from about 600 million years ago. Larger and more elaborate fossil burrows appear near 543 million years ago, the beginning of the Cambrian Period. Evidence of metazoan activity in both trace and body fossils then increased during the 13 million years leading to the explosion. All living phyla may have originated by the end of the explosion. Molecular divergences among lineages leading to phyla record speciation events that have been earlier than the origins of the new body plans, which can arise many tens of millions of years after an initial branching. Various attempts to date those branchings by using molecular clocks have disagreed widely. While the timing of the evolution of the developmental systems of living metazoan body plans is still uncertain, the distribution of Hox and other developmental control genes among metazoans indicates that an extensive patterning system was in place prior to the Cambrian. However, it is likely that much genomic repatterning occurred during the Early Cambrian, involving both key control genes and regulators within their downstream cascades, as novel body plans evolved.
PMID: 9927587 [PubMed - indexed for MEDLINE]
NOTAS DESTE BLOGGER:
O dilema de Darwin - ele sabia que o Cambriano era uma dificuldade tremenda para a sua teoria da evolução (mais particularmente a hipótese de descendência comum com modificação) continua sem resposta no contexto de justificação teórica (os darwinistas ortodoxos, fundamentalistas pós-modernos, chiques e perfumados a la Dawkins, odeiam o contexto de justificação teórica!!!).
O artigo de 1999 de Valentine, Jablonski e Erwin sugere que provavelmente teve de ocorrer muita repadronização genômica envolvendo os genes controladores e os reguladores à medida em que novos planos corporais evoluíam. O nome disso é MILAGRE!!!