Letter

Laser–Raman imagery of Earth's earliest fossils

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Abstract

Unlike the familiar Phanerozoic history of life, evolution during the earlier and much longer Precambrian segment of geological time centred on prokaryotic microbes1. Because such microorganisms are minute, are preserved incompletely in geological materials, and have simple morphologies that can be mimicked by nonbiological mineral microstructures, discriminating between true microbial fossils and microscopic pseudofossil ‘lookalikes’ can be difficult2,3. Thus, valid identification of fossil microbes, which is essential to understanding the prokaryote-dominated, Precambrian 85% of life's history, can require more than traditional palaeontology that is focused on morphology. By combining optically discernible morphology with analyses of chemical composition, laser–Raman spectroscopic imagery of individual microscopic fossils provides a means by which to address this need. Here we apply this technique to exceptionally ancient fossil microbe-like objects, including the oldest such specimens reported from the geological record, and show that the results obtained substantiate the biological origin of the earliest cellular fossils known.

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Acknowledgements

We thank M. Walsh for loan of the Kromberg specimens; The Natural History Museum, London, for loan of the Apex specimens; and J. Shen-Miller for manuscript review. This work was supported by grants from the JPL/CalTech Astrobiology Center (to J.W.S.) and from the National Aeronautics and Space Administration Exobiology Program (to T.J.W.). A.D.C. is an NSF predoctoral Fellow. The Raman imaging facility at the University of Alabama at Birmingham is a consequence of the vision of L. DeLucas.

Author information

Affiliations

  1. *Department of Earth & Space Sciences, and Institute of Geophysics & Planetary Physics (Center for the Study of the Evolution and Origin of Life), University of California, Los Angeles, California 90095-1567, USA

    • J. William Schopf
    •  & Andrew D. Czaja
  2. †Astro and Solar System Physics Program, Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294-1170, USA

    • Anatoliy B. Kudryavtsev
    • , David G. Agresti
    •  & Thomas J. Wdowiak

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Correspondence to J. William Schopf.

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