Discredited hypotheses for the Cambrian explosion

From Wikipedia, the free encyclopedia

 This article or section is in the middle of an expansion or major revamping.
You are welcome to assist in its construction by editing it as well.
Please view the edit history should you wish to contact the person who placed this template. If this article has not been edited in several days, please remove this template. Consider not tagging with a deletion tag unless the page hasn't been edited in several days.

As our understanding of the events of the Cambrian becomes clearer, data has accumulated to make some postulated causes for the Cambrian explosion look improbable. Some examples are the evolution of herbivory, vast changes in plate tectonic rates or orbital motion, or different evolutionary mechanisms in force.

[edit] The appearance of herbivorous organisms

Stanley (1973) suggested that the appearance about 700 million years ago of protists (single-celled eukaryotes) that "cropped" microbial mats greatly expanded food chains and thus allowed rapid diversification, which led to the Cambrian explosion.[1] But it is now thought that "cropping" arose before 1 billion years ago, as stromatolites began to decline about 1.25 billion years ago. [2][3]

[edit] Changes in orbital parameters

[edit] References

  1. ^ Stanley, S.M. (May 1973). "An Ecological Theory for the Sudden Origin of Multicellular Life in the Late Precambrian". Proc Natl Acad Sci U S A 70 (5): 1486–1489. doi:10.1073/pnas.70.5.1486. 
  2. ^ McNamara, K.J. (20 December 1996). "Dating the Origin of Animals". Science 274: 1993–1997. doi:10.1126/science.274.5295.1993f. 
  3. ^ Awramik, S.M. (19 November 1971). "Precambrian columnar stromatolite diversity: Reflection of metazoan appearance" (abstract). Science 174: 825–827. doi:10.1126/science.174.4011.825.