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Morphological and ecological complexity in early eukaryotic ecosystems

Nature volume 412, pages 6669 (05 July 2001) | Download Citation



Molecular phylogeny and biogeochemistry indicate that eukaryotes differentiated early in Earth history. Sequence comparisons of small-subunit ribosomal RNA genes suggest a deep evolutionary divergence of Eukarya and Archaea1; C27–C29 steranes (derived from sterols synthesized by eukaryotes) and strong depletion of 13C (a biogeochemical signature of methanogenic Archaea) in 2,700 Myr old kerogens independently place a minimum age on this split2,3. Steranes, large spheroidal microfossils, and rare macrofossils of possible eukaryotic origin occur in Palaeoproterozoic rocks4,5,6. Until now, however, evidence for morphological and taxonomic diversification within the domain has generally been restricted to very late Mesoproterozoic and Neoproterozoic successions7. Here we show that the cytoskeletal and ecological prerequisites for eukaryotic diversification were already established in eukaryotic microorganisms fossilized nearly 1,500 Myr ago in shales of the early Mesoproterozoic Roper Group in northern Australia.

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This paper is a contribution to the Australian Geological Survey Organization's NABRE project. We thank J. Jackson, P. Southgate and other members of the NABRE team for access to unpublished observations, helpful discussions, and advice on sampling. Core library staff in Canberra (AGSO) and Darwin (Northern Territory Geological Survey) greatly facilitated sample collection. Y. Leiming provided information on Chinese stratigraphy. Research supported in part by a grant from NASA, the NASA Astrobiology Institute, the Australia Research Council, and Macquarie University.

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  1. *Botanical Museum, Harvard University, Cambridge, Massachusetts 02138, USA

    • Emmanuelle J. Javaux
    •  & Andrew H. Knoll
  2. †Australian Centre for Astrobiology, Department of Earth and Planetary Sciences, Macquarie University, New South Wales 2109, Australia

    • Malcolm R. Walter


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