Advertisement

Journal of Molecular Evolution

, Volume 44, Supplement 1, pp S23–S27 | Cite as

The reason for as well as the consequence of the cambrian explosion in animal evolution

  • Susumu Ohno
Ancient molecular evolution

Abstract

The first 1 billion years of our 4.5-billion-year-old planet were extremely violent, chacarterized by constant meteorite bombardment. Therefore, it is with a great surprise that we note that cellular life flourished 3.5 billion years ago. It appears that the cellular life came into being as soon as the earth’s environment became hospitable. Because the main ingredient of the Archean sea was sodium bicarbonate, neither archeobacteria nor eubacteria but rather photosynthesizing organisms dominated—initially, prokaryotic cyanobacteria, soon joined by eukaryotic blue-green algae. These consumers of carbon dioxide were also releasers of molecular oxygen. The toil of 3 billion years by these releasers of molecular oxygen finally triggered the Cambrian animal explosion. With exceptions of two animal phyla, Porifera and Coelenterata, which amde slightly earlier appearances, nearly all other extant animal phyla sprang into almost simultaneous existence within 6 to 10 million years. The notion of the Cambrian pananimalia genome was advanced to explain various evolutionary consequences of this Cambrian explosion.

Key words

]Cambrian explosion Cellular life Pananimalia genome 

References

  1. Cavalier-Smith T (1988)Eukaryote cell evolution. Proceedings 13th International Botanical Congress, pp. 203–223Google Scholar
  2. Chang S (1994) The planetary setting of prebiotic evolution. In Bengston S (ed) Early life on earth (Nobel symposium No. 84). Columbai University Press, New YorkGoogle Scholar
  3. Chen J-Y, Dzik J, Edgecomb GD, Ramskold L, Zhou G-Q (1995) A possible early Cambrian chordate. Nature 377:720–722CrossRefGoogle Scholar
  4. Clourd P, Glaesner MF (1982) The Edicarian period and system: Metazoa inherit the earth. Science 218:783–792CrossRefGoogle Scholar
  5. Conway Morris S (1989) Burgess shale faunas and the Cambrian explosion. Science 246:339–346CrossRefGoogle Scholar
  6. Courties C, Vaquer A, Troussellier M, Lautier J, Chertiennot-Dimer MJ, Neveaux J, Machado C, Claustre H (1994) Smallest eukaryotic organism. Nature 370:255–256CrossRefGoogle Scholar
  7. Gabbot SE, Aldridge RJ, Theron JM (1995) A giant conodont with preserved muscle from the upper Ordovician of South Africa. Nature 374:800–803CrossRefGoogle Scholar
  8. Gould SJ (1995) Of it and not above it. Nature 377:681–682CrossRefGoogle Scholar
  9. Kempe S, Degens ET (1985) An early soda water ocean? Chem Geol 53:95–104CrossRefGoogle Scholar
  10. Kumada Y, Benson DR, Hillemann D, Hosted TJ, Thompson CJ, Wohlleben W, Tateno Y (1993) Evolution of the glutamine synthetase gene; one of the oldest existing and functioning genes. Proc Natl Acad Sci USA 90:3009–3013PubMedCrossRefGoogle Scholar
  11. Lewis EB (1978) A gene complex controlling segmentation in Drosophila. Nature 276:567–570Google Scholar
  12. Ohno S (1996) The notion of the Cambrian pananimalia genome. Proc Natl Acad Sci USA 93:8475–8478PubMedCrossRefGoogle Scholar
  13. Schopf JW (1993) Microfossils of the early Archean apex chert: new evidence of the antiquity of life. Science 260:640–646PubMedCrossRefGoogle Scholar
  14. Shiroyama Y (1996) Nematodes in all shapes (in Japanese). Kagaku (Tokyo) 66:312–317Google Scholar

Copyright information

© Springer-Verlag 1997

Authors and Affiliations

  • Susumu Ohno
    • 1
  1. 1.Beckman Research Institute of the City of HopeDuarteUSA

Personalised recommendations