Title

Abstract

CV

Back

Staring KNGMG/NGMSO symposium

Dr. mrs. F. Westall

Title

Early evolution of life on Earth

Abstract

Life of Earth appeared in a specific geological context and its early evolution took place alongside the geological evolution of the Earth. However, the greatest problem facing investigation of the first billion years in the history of the Earth is the lack of material "evidence": the dynamic activity of plate tectonics has all but obliterated the early rock record. Moreover, there is much dissention as to the interpretation of the few, highly metamorphosed remnants found in the ancient cratons. What information do we have about the earliest period in Earth's history and what are the changes that brought about the "modern" Earth? How do they affect the evolution of life?

Ancient detrital zircons dating to 4.4. b.y. ago provide evidence for a considerable amount of water at the surface of the Earth by that date and testify to the presence of protocontinents [1]. Since life needs water, organics and energy, it could conceivable had originated already by 4.4 b.y. Extermination of life by massive impacts has been hypothesised [2] but there is no proof that this occurred. The oldest (equivocal) indications of life, based on carbon isotope studies of the oldest preserved supracrustal rocks at Isua, W. Greenland, date back to >3.75 b.y. ago [3]. Although there are older metamorphosed terrains, the oldest well-preserved supracrustal rocks occur in the Pilbara, NW Australia, and in the Barberton greenstone belt, W. South Africa. Both terrains cover a critical transition period between an early Earth characterised by an apparently mixed, vertical plume and shallow plate tectonic regime and a basically modern plate tectonic regime (>3.5-ca. 2.9 b.y.). The Early Archaean portion of this rock record documents widespread life in the form of microbial mats in shallow water environments that were probably hot (pervasive hydrothermal activity) and salty [4]. The mats were constructed and inhabited by a variety of microorganisms including small filamentous, rod-shaped and coccoidal forms (probably anoxygenic photosynthesisers, chemolithotrophs and heterotrophs).

Despite previous descriptions [5], there is no evidence for the presence of oxygenic cyanobacteria in the Early Archaean (indeed, genomic timescales suggest that the latter appeared about 2.6 b.y. ago [6]). The oldest bona fide observations of cyanobacteria date back to the 2.59 b.y.- old Cambellrand Subgroup in South Africa [7], although carbonaceous biomarkers from the 2.7 b.y. Hammersley Group shales in NW Australia suggest that they were present when those sediments were deposited [8]. By this period, the Earth was tectonically similar to the modern Earth: cratonisation had led to the formation of true continental masses, there is clear evidence for lateral plate tectonic motion, and wide continental platforms were forming around the continents. In fact, the domal stromatolites, so characteristic of much of the Proterozoic, typically occurred on such shallow carbonate platforms [9].

In terms of eukaryote evolution, it appears that the lineage giving rise to the eukaryotes spilt off from the archaebacteria already by about 4.0 b.y. ago [6]. Steranes, a group of macromolecular derivatives of eukaryotes, occur in the 2.7 b.y.-old Hammersley Group shales, hinting at organisms with some eukaryote characteristics by this time [10]. However, genomic studies suggest that two specific occurrences of lateral gene transfer took place by symbiosis: a premitochondrial transfer at about 2.7 b.y. ago and a later mitochondrial transfer (involving cyanobacteria) at about 1.8 b.y. [6]. It is probably impossible to directly identify the first eukaryote microfossils on the basis of morphology alone since they are likely to have had similar size and shape relationships to bacteria. In fact, the oldest interpreted eukaryotic microfossils consist of acritarchs dating back to 2.1 b.y. [11].

One phenomenon, which occurred at the same time as the evolution of cyanobacteria and eukaryotes, is the rise in atmospheric oxygen [12]. For a long time it was believed that oxygenic photosynthesis by cyanobacteria was responsible but the removal of carbon from the atmosphere through the burial of organic matter and carbonates by plate tectonic activity may have been equally or even more significant in this process. Whatever the underlying reason, there seems to have been a clear relationship between the rise of oxygen in the atmosphere and the evolution of eukaryotes.

Thus we see that the early geological evolution of the Earth and the early evolution of life occurred in parallel. However, it is important to recall that microbial processes are surface-specific and that, although large-scale geological events form a global context for the evolution of life, there may be no direct cause and effect mechanism.

[1] Wilde, S.A. et al. (2001) Nature, 409 : 175-178.
[2] Sleep, N.H. et al. (1989) Nature, 342 : 139-142.
[3] Schidlowsky, M. (1988) Nature, 333 : 313-318; Mojzsis, S., et al. (1996), Nature, 384 : 55-57 ; Rosing, M. (1999) Science, 283 : 674-676.
[4] Walsh,M.M. (1992) Precambrian Research, 54 : 271-293; Westall, F. et al., (2001) Precambrian Research, 106 : 93-116.
[5] Schopf, J.W. (1993) Science, 260 : 640-646.
[6] Hedges, S.B. et al. (2001) BMC Evolutionary Biology, 1 : 4-14.
[7] Altermann and Schopf (1995) Precambrian Research, 75 : 65-90.
[8] Summons, R.E. et al. (1999) Nature, 400 : 554-557.
[9] Grotzinger, J.P. (1994) In Early Life on Earth (Ed.) S. Bengtson, Columbia Univ. Press, pp.245-258.
[10] Brocks, J.J. (1999) Science, 285 : 1033-1036.
[11] Han, T.M. and Runnegar,B. (1992) Science, 257 : 232-235.
[12] Holland, H.D. (1994) In Early Life on Earth (Ed.) S. Bengtson, Columbia Univ. Press, pp.237-244.

Curriculum Vitae

Date and place of birth: 20.6.1955, Johannesburg, R.S.A.
Nationality:     British (Passport No. C 788694 D)
Home address: via Torino 10, 40139 Bologna, Italy
Work Address: (from 1.1.2002) Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, 45071 Orléans cedex 2, France
(until 31.1.2001) Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston TX 77058, USA.
Telephone: +39-051-492154
Fax      : +39-051-492154
Email   : frances.westall@tin.it

Occupation: Directeur de Recherche (Exobiology), CNRS, Orléans, France (from 1.1.2002)

Higher Education

1973-1977        University of Edinburgh, U.K.                  BSc Honours (Geology)
1977-1984        University of Cape Town, R.S.A.                PhD (Marine Geology)
                 (Current-controlled sedimentation in the Agulhas Passage, SW Indian Ocean)

Field of Expertise

· Earliest life on Earth and its geological context:  Field studies of the earliest supracrustal terrains and study of the fossil bacteria from the Early Archaean.
· Search for life on Mars and human exploration of Mars: Bacteriomorph structures in Martian meteorites, future astronaut training with respect to searching for traces of fossil life.

Professional career

· January 2002 Directeur de Recherche, Equipe Exobiologie, Centre de Biophysique Moléculaire, CNRS, Orléans (Expansion of present, prebiotic research field of laboratory to bacterial palaeontology, early Earth geological history, Martian geology and potential palaeontology, astronaut training in exobiology)
· March 2000 2001 Visiting post doctoral scientist, Lunar and Planetary Institute, Houston, USA. (bacterial palaeontology, prebiotic molecules, Early Archaean geology and bacterial palaeontology, fieldwork in Australia and South Africa)
· March 1998- February 2000 - NRC Fellow, Johnson Space Center, Houston, USA. (bacteriomorphs in Martian meteorites, bacterial palaeontology, fieldwork in Greenland and South Africa)
· October 1991 -February 1998 -  E.C. postdoctoral researcher, University of Bologna, Italy. (Experimental fossilisation of bacteria and DNA, bacterial palaeontology, research cruise to South Atlantic)
· March 1989-October 1991 E.C. postdoctoral researcher at the University of Nantes, France. (Bacterial palaeontology and bacteria-sediment interactions, field work W. coast France)
· November 1984-October 1989 - Postdoctoral research fellow, Alfred Wegener Institute, Bremerhaven, West Germany (palaeooceanography, research cruises to S. Atlantic)

Highlights

· 1977-1992:Numerous research cruises to the SW Indian Ocean, Antarctic-South Atlantic
· Field seasons in Early Archaean terrains of W. Greenland, Pilbara and Barberton
· 1997-1998: European Space Agency exobiology study group
· 2000: European Space Foundation chair for Exobiology

Publications

More than 170 publications (peer-reviewed papers, book chapters. Proceedings chapters, conference abstracts, reports).
Some selected publications below:
WESTALL, F., DE WIT, M.J., DANN, J., VAN DER GAAST., S., DE RONDE., C., GERNEKE., D., 2001.  Early Archaean fossil bacteria and biofilms in hydrothermally influenced, shallow water sediments, Barberton Greenstone Belt, South Africa. Precambrian Research, 106, 91-112.
GIBSON, E.K., MCKAY, D.S., THOMAS-KEPRTA, K., WENTWORTH, S.J., WESTALL., F., STEELE, A., ROMANEK, C.S., BELL, M.S., and TOPORSKI, J., 2001. Life on Mars: Evaluation of the evidence within Martian meteorites ALH84001, Nakhla and Shertgotty. Precambrian Research, 106, 13-32.
ALLEN, C.C. WESTALL, F., and SCHELBLE, R., 2001. Importance of a Martian hematite site for Astrobiology. Astrobiology, 1: 111-123.
WESTALL, F., WALSH, M., STEELE, A., TOPORSKI, J., DE RONDE, C., and DE WIT, M., 2001. Life in the solar system: what are we looking for and what can we learn from the early terrestrial fossil record? Rencontres de Blois, 2000, in press.
WALSH, M.M. and WESTALL, F., 2001. Archean biofilms preserved in the 3.2-3.6 Ga Swaziland Supergroup, South Africa. In Fossil and Recent Biofilms (ed. W.E. Krumbein, T. Dornieden, and M. Volkmann), Kluwer, Amsterdam, in press.
WESTALL, F., NIJMAN, W., BRACK, A., STEELE, A. and TOPORSKI, J., 2001. The oldest fossil life on Earth, its geological context and life on Mars. ESA Spec. Pub. In press.
WESTALL, F. and WALSH, M.M., 2001. Phanerozoic fossil endoliths in Early Archaean fossiliferous rocks: implications for the detection of martian endoliths. Planet. Space Sci., submitted.
WESTALl, F., and WALSH, M.M., 2001. Fossil biofilms and the search for life on Mars. In Fossil and Recent Biofilms (ed. W.E. Krumbein, T. Dornieden, and M. Volkmann), Kluwer, Amsterdam, in press.
TOPORSKI, J., MCKAY, D.S., STEELE, F., and WESTALL, F., 2001. Bacterial biofilms in astrobiology: the importance of life detection. In Fossil and Recent Biofilms (ed. W.E. Krumbein, T. Dornieden, and M. Volkmann), Kluwer, Amsterdam, in press.
WESTALL, F., WALSH, M.M., DE VRIES, S., and NIJMAN, W. Fossil microbial biofilms from Early Archaean volcaniclastic sediments.
STEELE, A., WHITBY, C., GRIFFIN, C., TOPORSKI, J., WESTALL, F., SAUNDERS, J., and MCKAY, D.S., 2001. Microbial contamination of Allende and Murichison carbonaceous  chondrites: developing a protocol for life detection in extraterrestrial materials using biotechnology. Proc. Natl. Acad. Sci., in press.
WESTALL, F., STEELE, A., TOPORSKI, J. WALSH, M., ALLEN, C., GUIDRY, S., GIBSON, E., McKAY, D., and CHAFETZ, H., Polymeric substances and biofilms as biomarkers in terrestrial materials: Implications for extraterrestrial samples. J. Geophys. Res. Planets. 105:24,511-24,527.
TOPORSKI, J.K.W., STEELE, A., WESTALL, F., AVCI, R., MARTILL, D.M., and MCKAY, D.S.,  In-situ biomarker detection using ToF-SIMS and high resolution electron microscopy imaging of an exceptionally well preserved bacterial biofilm from the 28 million year old Enspel Formation.  Geoch. Cosmoch. Acta, in press.
TOPORSKI, J.K.W., WESTALL, F., THOMAS-KEPRTA, K.A., STEELE, A., and MCKAY, D.S. The simulated silicification of bacteria new clues to the modes and timing of bacterial preservation and implications for the search for extraterrestrial microfossils. Astrobiology, in press.
ALLEN, C.C., ALBERT, F.G., COMBIE, J., CHAFETZ, H., GRAHAM, C.R., KIEFFT., T., KIVETT, S.J.,  MCKAY, D.S., STEELE, A., TAUNTON, A., TAYLOR, M.R., THOMAS-KEPRTA, K. and WESTALL, F., 2000. Microscopic  physical biomarkers in carbonate thermal hot springs: implications in the search for life on Mars. Icarus, 49-67.
SECKBACH, J, WESTALL, F., and CHELA-FLORES, J., 2000. Introduction to Astrobiology:Origin, Evolution, Distribution and Destiny of Life in the Universe. . In J. Seckbach (Ed.) Microbial Diversity, Kluwer, Amsterdam, in press.
WESTALL, F. and WALSH, M.M., 2000. The diversity of fossil microorganisms in Archaean-age rocks. In J. Seckbach (Ed.) Microbial Diversity, Kluwer, Amsterdam, in press.
WESTALL, F., Exobiology, mineral signatures, and the search for extraterrestrial life. In Exobiologie, les traces du vivant et lorigine de la vie, M. Gargaud (Ed). Proc. Ecole Thématique La Colle sur Loup, in press. MCKINLEY, J.P., STEVENS, T.O. and WESTALL, F. 2000.  Microfossils and paleoenvironments in deep subsurface basalt samples.  Geomicrobiololy Journal, 17: 1-12.
WESTALL, F., BRACK, A., HOFMANN, B., HORNECK, G., KURAT, G., MAXWELL, J., ORI, G.G., PILLINGER, C., RAULIN, F., THOMAS, N., FITTON, B., CLANCY, P. 2000.  An ESA study for the search for life on Mars. Planetary and Space Science, 48: 181-202.
WESTALL, F. 1999. Fossil bacteria. In  J. Seckbach (Ed). Enigmatic microorganisms and life in extreme environments. Kluwer, Amsterdam, pp 74-88, .
BARBIERI, R., D'ONOFRIO, S., WESTALL, F., and MELIS, R., 1999. Calcified bacteria on benthic foraminfera from Antarctic sediments. Palaeoecology, Palaeogeography, Palaeoclimatology,149: 45-61.
WESTALL, F., 1999.  The nature of fossil bacteria: A guide to the search for extraterrestrial life. Journal of Geophysical Research, Planets, 104, 16,437-16,451.
WESTALL, F. and WALSH, M.M., 2000. The diversity of fossil microorganisms in Archaean-age rocks. In J. Seckbach (Ed.) Microbial diversity. Kluwer, Amsterdam, in press.
WESTALL, F. and GERNEKE, D. 1998. Electron microscope methods in the search for the earliest life forms on Earth (in 3.5-3.3 Ga cherts from the Barberton greenstone belt, South Africa): applications for extraterrestrial life studies. SPIE, Instruments, Methods and Missions for Astrobiology, 3114, San Diego, July, 1998. 158-169.
WESTALL, F., GOBBI, P., MAZZOTTI, G., GERNEKE, D., STARK, R., DOBREK, T., and HECKL, W. 1998. Combined SEM (secondary electrons, backscatter, cathodoluminescence) and atomic force microscope investigation of the carbonate globules in Martian meteorite ALH84001: preliminary results. SPIE, Instruments, Methods and Missions for Astrobiology, 3114, 225-233.
MCKAY, D.S., ROZANOV, A.Y., HOOVER, R.B. and WESTALL, F. 1998. Phosphate biomineralisation of Cambrian microorganisms. SPIE, Instruments, Methods and Missions for Astrobiology, 3114, San Diego, July, 1998.
WESTALL, F., 1998. The oldest fossil mineral bacteria from the Early Archean of South Africa and Australia. In J. Chela-Flores and F. Raulin (Eds.) Exobiology: Matter, Energy, and Information in the Origin and Evolution of Life in the Universe. Kluwer, Amsterdam, 181-186.
WESTALL, F. GOBBI, P., GERNEKE, D., and MAZZOTTI, G., 1998. Ultrastructure in the carbonate globules of Martian meteorite ALH84001. In J. Chela-Flores and F. Raulin (Eds.) Exobiology: Matter, Energy, and Information in the Origin and Evolution of Life in the Universe. Kluwer, Amstredam, 245-250.
WESTALL, F., 1997. The influence of cell wall composition on the fossilisation of bacteria and the implications for the search for early life forms. In C. B. Cosmovici, S. Bowyer, and D. Werthimer (Eds.) Astronomical and Biochemical Origins and the Search for Life in the Universe, Editrici Compositori, Bologna, 491-504.
LIEBIG, K., WESTALL, F., and SCHMITZ, M., 1996., A study of fossil microstructures from the Eocene Messel Formation using transmission electron microscopy. Neues. Jh. Geol. Paläont. Mh., 4, 218:231.
WESTALL, F., BONI, L., and GUERZONI, M.E., 1995. The experimental silicification of microbes. Palaeontology 38: 495-528.
WESTALL, F. and RINCE, Y., 1994.  The biofilm and microbe-particle interactions: examples from diatomaceous sediments. Sedimentology, 41: 147-162.
WESTALL, F., 1994. Silicified bacteria and associated biofilm from the deep-sea sedimentary environment. Kaupia- Darmstdter Beitrge zur Naturgeschichte, 4: 29-43.
WESTALL, F., ROSSI, S., and MASCLE, J., 1993. Current-controlled sedimentation in the Equatorial Atlantic: The southern margin of the Guinea Plateau and the Romanche Fracture Zone. Sediment. Geol., 82: 157-171.
MONTY, C.L.V., WESTALL., and VAN DER GAAST, S., 1991. The diagenesis of siliceous particles in Subantartcic sediments, ODP Leg 114, Hole 699: possible microbial mediation. In Ciesielski, P.F., Kristoffersen, Y. et al., (Eds), Proc. ODP Sci. Results, 114: College Station, TX (Ocean Drilling Program), pp 685-710.