and oxygen isotope (δ18O) stratigraphy: Kane Gap core, east equatorial Atlantic Ocean, 1984 122Frontispiece: fossil molecules in geologic time vi
A synthesis of information from numerous sources (see bibliographies for chapters 5, 9, and 10)
Column chromatography 1
Gas chromatograph, 1950s p
Normal alkanes: different representations used to understand molecular behavior 10
Some examples of functional groups in organic compounds 11
Gas chromatograms of leaf wax alkanes 12
After Eglinton, G., A. G. Gonzalez, R. J. Hamilton, and R. A. Raphael. 1962. Hydrocarbon constituents of the wax coatings of leaves: A taxonomic survey. Phytochemistry 1:89–102 (top); and Rommerskirchen, F., A. Plader, G. Eglinton, Y. Chikaraishi, and J. Rullkötter. 2006. Chemotaxonomic significance of distribution and stable carbon isotopic composition of long-chain alkanes and alkan-1-ols in C4 grass waxes. Organic Geochemistry 37:1303–1332 (bottom).
Comparing alkane histograms, 1962: two genera of Canary Island succulents 14
After Eglinton, G., R. J. Hamilton, R. A. Raphael, and A. G. Gonzalez. 1962. Hydrocarbon constituents of the wax coatings of plant leaves: A taxonomic survey. Nature 193:739–742; and Eglinton, G., A. G. Gonzalez, R. J. Hamilton, and R. A. Raphael. 1962. Hydrocarbon constituents of the wax coatings of leaves: A taxonomic survey. Phytochemistry 1:89–102.
Biosynthesis of unbranched carbon chains: odd versus even numbers of carbon atoms 15
Ancient rocks, 1960s 19
Microfossils in the Gunflint chert: 1960s microphotographs 20
After Barghoorn, E. S., and S. A. Tyler. 1965. Microorganisms from the Gunflint chert. Science 147:563–577.
Analysis of hydrocarbons in ancient shales 22
Identifying pristane in the 50-million-year-old Green River shale 23
After Eglinton, G., and M. Calvin. 1967. Chemical fossils. Scientific American 216:32–43.
Head-to-tail isoprenoid link 24
Geological transformation of chlorophyll a 25
The one-billion-year-old Nonesuch shale: gas chromatograms of alkanes, packed column, 1964 26
After Eglinton, G., P. M. Scott, T. Belsky, A. L. Burlingame, W. Richter, and M. Calvin. 1966. Occurrence of isoprenoid alkanes in a Precambrian sediment. In: Hobson, G. D., and M. C. Louis, eds., Advances in Organic Geochemistry 1964, Pergamon Press (London): 41–74.
Cell membrane 29
Based on a figure in Ourisson, G., and Y. Nakatani. 1994. The terpenoid theory of the origin of cellular life: The evolution of terpenoids to cholesterol. Chemistry and Biology 1:11–23.
Fatty acid structures 31
Optical stereoisomers 34
Phytol, and the stereoisomers of phytanic acid 35
Isomerization of α-amino acids 37
Oil migration and accumulation 51
After Tissot, B. P., and D. H. Welte. 1984. Petroleum Formation and Occurrence, 2nd ed., Springer (Heidelberg, Germany): 294.
Oil drop with hydrocarbon structures 52
Biosynthesis of sterols and pentacyclic triterpenoids: a simplified scheme 54
Some sterols and triterpenoids found in organisms 55
Steranes and pentacyclic triterpanes found in petroleum and rocks 57
Mass spectra of steranes and pentacyclic triterpanes 60
Mass spectrum of 17α-hopane 62
Bacteriohopanetetrol (C35H62O4) 65
Hydrocarbon generation profiles 69
After Tissot, B. P., and D. H. Welte. 1984. Petroleum Formation and Occurrence, 2nd ed., Springer (Heidelberg, Germany): 180.
n-Alkane distributions at various depths in Douala Basin shale 70
After Albrecht, P., and G. Ourisson. 1969. Diagénèse des hydrocarbures saturés dans une série sédimentaire épaisse (Douala, Cameroun). Geochimica et Cosmochimica Acta 33:138–142.
Gas chromatogram showing extended hopanes, 1975: deeply buried early Jurassic shale, Paris Basin 72
After Ensminger, A., P. Albrecht, and G. Ourisson. 1977. Evolution of polycyclic alkanes under the eff ect of burial (early Toarcian shales, Paris basin). In: Campos, R., and J. Goñi, eds., Advances in Organic Geochemistry 1973, Editions Technip (Madrid): 45–52.
Chiral centers, ring labels, and carbon atom numbering in hopanes and steranes 75
Mass spectra of 17β, 21β-hopanes versus 17α, 21β-hopanes (C31H54) 76
Three-dimensional models of hopane stereoisomers 77
Hopane stereoisomers in an immature rock and a crude oil 78
Mass fragmentograms for biomarkers in crude oil 80
Three-dimensional models of sterane stereoisomers 84
Diasterane structure 85
Aromatization 86
Transformation of biomarkers with increasing maturity 87
A schematic representation, based on Mackenzie, A. S. 1984. Application of biological markers in petroleum geochemistry. In: Brooks, J., and D. Welte, eds., Advances in Petroleum Geochemistry, Vol. 1, Academic Press (New York): 115–214.
Changes in amounts of hopane and sterane stereoisomers with burial depth: Barents Sea core, Eocene claystone, 1998 93
After Farrimond, P., A. Taylor, and N. Telnæs. 1998. Biomarker maturity parameters: The role of generation and thermal degradation. Organic Geochemistry 29:1181–1197.
Kerogen and biomarkers: the journey from organisms to petroleum 95
A schematic representation, after Tegelaar, E. W., J. W. de Leeuw, S. Derenne, and C. Largeau. 1989. A reappraisal of kerogen formation. Geochimica et Cosmochimica Acta 53:3103–3106.
Some organic sulfur compounds and possible precursors 97
Deep sea drilling 102
Diagenesis of steroids and hopanoids 105
Molecular analysis of alcohols in immature marine sediments 107
Dinosterol, and some dinoflagellates 108
The scanning electron micrographs of dinoflagellates are by Maria A. Faust at the Smithsonian National Museum of Natural History, used by permission. The top left image is of Ornithocercus magnificus, bottom left is Ceratochoris horrida, and bottom right is Protoperidinium crassipes. © Smithsonian Institution.
Alkane diols 109
Highly branched isoprenoid (HBI) 110
Emiliania huxleyi cells, scanning electron micrograph 112
Courtesy of Jane Lewis, University of Westminster.
Alkenones in Emiliania huxleyi 114
After Prahl, F. G., L. A. Muehlhausen, and D. L. Zahnle. 1988. Further evaluation of long-chain alkenones as indicators of paleoceanographic conditions. Geochimica et Cosmochimica Acta 52:2303–2310.
Orbital variations 116
Alkenone distributions: Japan Trench and Middle American Trench 119
Based on Brassell, S. C. 1993. Applications of biomarkers for delineating marine paleoclimatic fluctuations during the Pleistocene. In: Engel, M. H., and S. A. Macko, eds., Organic Geochemistry—Principles and Applications, Plenum Press (New York): 699–738.
Average degree of unsaturation versus algal growth temperature for long-chain unsaturated lipids in Emiliania huxleyi, 1982 121
After Marlowe, I. T. 1984. Lipids as Paleoclimatic Indicators. Ph.D. thesis, University of Bristol.
Alkenone unsaturation and oxygen isotope (δ18O) stratigraphy: Kane Gap core, east equatorial Atlantic Ocean, 1984 122
After Brassell, S. C., G. Eglinton, I. T. Marlowe, U. Pflaumann, and M. Sarnthein. 1986. Molecular stratigraphy: A new tool for climatic assessment. Nature 320:129–133.
Calibration of 
from suspended and sinking particulate matter, 1987 124
After Prahl, F. G., and S. G. Wakeham. 1987. Calibration of unsaturation patterns in long-chain ketone compositions for paleotemperature assessment. Nature 330:367–369.
cis and trans double bonds in fatty acids and alkenones 125
Worldwide calibration of in surface sediments, 1998 127
After Müller, P. J., G. Kirst, G. Ruhland, I. von Storch, and A. Rosell-Melé. 1998. Calibration of the alkenone paleotemperature index based on core-tops from the eastern South Atlantic and the global ocean (60°N–60°S). Geochimica et Cosmochimica Acta 62:1757–1772.
First alkenone record of abrupt climate oscillations, 1991: comparison with the foram δ18O record of three glacial cycles, tropical northeast Atlantic 129
After Eglinton, G., S. A. Bradshaw, A. Rosell, M. Sarnthein, U. Pflaumann, and R. Tiedemann. 1992. Molecular record of secular sea surface temperature changes on 100-year timescales for glacial terminations I, II and IV. Nature 356:423–426.
Records of abrupt climate oscillations: alkenones and δ18O 130
After B. Martrat, J. O. Grimalt, C. Lopez-Martinez, I. Cacho, F. J. Sierro, J. Abel Flores, R. Zahn, M. Canals, J. H. Curtis, and D. A. Hodell. 2004. Abrupt temperature changes in the Western Mediterranean over the past 250,000 years. Science 306:1762–1765; and Seki, O., R. Ishiwatari, and K. Matsumoto. 2002. Millennial climate oscillations in NE Pacific surface waters over the last 82 kyr: New evidence from alkenones. Geophysical Research Letters 29:2144–2148.
From paleoclimates to historical climates: an alkenone 
record of sea surface temperatures off the north coast of Iceland 131
After Sicre, M., J. Jacob, U. Ezata, S. Rousse, C. Kissel, P. Yioua, J. Eiríksson, K. L. Knudsen, E. Jansen, and J. Turon. 2008. Decadal variability of sea surface temperatures off North Iceland over the last 2000 yrs. Earth and Planetary Science Letters 268:137–142.
Ocean circulation: the great conveyor belt 132
Modified from W. S. Broecker. 1991. The great ocean conveyor. Oceanography 4:79–89.
Upwelling 133
Proposed reaction mechanism for β-amyrin-type pentacyclic triterpenoid diagenesis 136
Solving the oleanane riddle: proposed scheme for the diagenesis of pentacyclic triterpenoids from plants 137
After ten Haven, H. L., T. M. Peakman, and J. Rullkötter. 1992. Early diagenetic transformation of higher-plant triterpenoids in deep-sea sediments from Baffin Bay. Geochimica et Cosmochimica Acta 56:2001–2024.
Some diatom biomarkers 140
All diatom scanning electron micrographs and microphotographs are images made available by the Plankton*Net Data Provider at the Alfred Wegener Institute for Polar and Marine Research, hdl:10013/de.awi.planktonnet. The images of Thalassiosira angulata, Thalassiosira rotula, Thalassiosira punctigera, and Rhizosolenia setigera are by Mona Hoppenrath at the Alfred Wegener Institute. Pleurosigma sp. is by Daniel Vaulot at the Roscoff Station Biologique.
Organic matter accumulation and preservation 143
Biomarkers for anoxia in the photic zone: pigments and fossil molecules from green sulfur bacteria 145
Lycopane 146
Mediterranean sapropels: the biomarker story (mid-Pleistocene period) 149
After Rinna, J., B. Warning, P. A. Meyers, H.-J. Brumsack, and J. Rullkötter. 2002. Combined organic and inorganic geochemical reconstruction of paleodepositional conditions of a Pliocene sapropel from the eastern Mediterranean Sea. Geochimica et Cosmochimica Acta 66:1969–1986.
Oceanic anoxic events: biomarkers for anoxia in Cretaceous black shales 151
Based on Pancost, R. D., N. Crawford, S. Magness, A. Turner, H. C. Jenkyns, and J. R. Maxwell. 2004. Further evidence for the development of photic-zone euxinic conditions during Mesozoic oceanic anoxic events. Journal of the Geological Society 161:353–364. Map provided by C. R. Scotese’s PALEOMAP Project (www.scotese.com), plate tectonic maps, and continental drift animations.
Typical δ13C values in organisms, the environment, and geologic deposits 158
Isotope data from Schidlowski, M. 1988. A 3,800–million-year isotopic record of life from carbon in sedimentary-rocks. Nature 333:313–318; and Schidlowski, M. 2000. Carbon isotopes and microbial sediments. In: Riding, R., and S. M. Awramik, eds., Microbial Sediments, Springer (Heidelberg, Germany): 84–95.
Carbon isotope fractionation during photosynthesis 162
Developing a proxy for atmospheric CO2 , 1990: estimates of CO2 concentrations during the last ice age cycle based on the δ13C of alkenones and foraminifera in a Gulf of Mexico core 165
After Jasper, J. P., and J. M. Hayes. 1990. A carbon isotope record of CO2 levels during the late Quaternary. Nature 347:462–464.
Relationship between photosynthetic isotope fractionation (εp), growth rate, and dissolved CO2 concentration in a laboratory culture of Emiliania huxleyi
After Bidigare, R. R., A. Fluegge, K. H. Freemann, K. L. Hansson, J. M. Hayes, D. Hollander, J. P. Jasper, L. L. King, E. A. Laws, J. Milder, et al. 1997. Consistent fractionation of 13C in nature and in the laboratory: Growth-rate effects in some haptophyte algae. Global Biogeochemical Cycles 11:279–292.
The history of CO2 and climate 168
After Pagani, M., J. C. Zachos, K. H. Freeman, B. Tipple, and S. Bohaty. 2005. Marked decline in atmospheric carbon dioxide concentrations during the Paleogene. Science 309:600–603.
C3 versus C4 plants: n-alkane distributions and δ13C values 170
After Rommerskirchen, F., G. Eglinton, L. Dupont, and J. Rullkötter. 2006. Glacial/inter-glacial changes in southern Africa: Compound-specific δ13C land plant biomarker and pollen records from southeast Atlantic continental margin sediments. Geochemistry Geophysics Geosystems 7:Q08010 (doi:10.1029/2005GC001223); and Rommerskirchen, F., A. Plader, G. Eglinton, Y. Chikaraishi, and J. Rullkötter. 2006. Chemotaxonomic significance of distribution and stable carbon isotopic composition of long-chain alkanes and alkan-1-ols in C4 grass waxes. Organic Geochemistry 37:1303–1332.
Mapping with biomarkers and plant pollen: comparing interglacial and glacial African ecosystems 172
After Rommerskirchen, F., G. Eglinton, L. Dupont, U. Güntner, C. Wenzel, and J. Rullkötter. 2003. A north to south transect of Holocene southeast Atlantic continental margin sediments: Relationship between aerosol transport and compound-specific δ13C land plant biomarker and pollen records. Geochemistry Geophysics Geosystems 4(12):1101 (doi:10.1029/2003GC000541); and Rommerskirchen, F., G. Eglinton, L. Dupont, and J. Rullkötter. 2006. Glacial/interglacial changes in southern Africa: Compound-specific δ13C land plant biomarker and pollen records from southeast Atlantic continental margin sediments. Geochemistry Geophysics Geosystems 7:Q08010 (doi:10.1029/2005GC001223).
Did Cretaceous oceanic anoxic events allow C4 land plants to become more prevalent? 174
Evidence from a DSDP core off the coast of northwest Africa. After Kuypers, M. M. M., R. D. Pancost, and J. S. Sinninghe Damsté. 1999. A large and abrupt fall in atmospheric CO2 concentration during Cretaceous times. Nature 399:342–345.
A hydrothermal vent landscape (1980, East Pacific Rise) 178
From Haymon, R. M. 1982. Hydrothermal Deposition on the East Pacific Rise at 21°N. Ph.D. dissertation, University of California, San Diego. Courtesy of Rachel M. Haymon.
Woese’s universal phylogenetic tree, 1987 179
After Woese, C. R. 1987. Bacterial evolution. Microbiological Reviews 51:221–271.
Examples of unusual lipids in archaea 180
Microbial mats from around the world 184
The photos of cyanobacteria and of the Solar Lake core are courtesy of Bo Barker Jørgensen at the Max Planck Institute for Marine Biology. The photo of the Yellowstone mat is courtesy of David Ward at Montana State University Bozeman.
A microbial mat community from an alkaline hot spring: schematic representation of a vertical profile 187
Based on Ward, D. M., J. Jentaie, Y. Bing Zeng, G. Dobson, S. C. Brassell, and G. Eglinton. 1989. Lipic biochemical markers and the composition of microbial mats. In Microbial Mats: Physiological Ecology of Benthic Microbial Communities, American Society for Microbiology (Washington, DC); Zeng, Y. B., D. M. Ward, S. C. Brassell, and G. Eglinton. 1992. Biogeochemistry of hot spring environments 3. Chemical Geology 95:347–360; and David Ward, personal communication.
Microbial breakdown of organic matter in marine sediments 189
Based on Jørgensen, B. B. 2006. Bacteria and marine biogeochemistry. In: Schulz, H. D., and M. Zabel, eds., Marine Geochemistry, 2nd ed., Springer-Verlag (Heidelberg, Germany): 169–206.
Distribution of methane hydrates, 2002 191
After Kvenvolden, K. A., and B. W. Rogers. 2005. Gaia’s breath—global methane exhalations. Marine and Petroleum Geology 22:579–590.
Methane oxidation and 13C-depleted crocetane in Kattegat Strait sediments 193
After Bian, L. Q., K.-U. Hinrichs, T. M. Xie, S. C. Brassell, J. P. Beck, N. Iversen, H. Fossing, B. B. Jørgensen, and J. M. Hayes. 2001. Algal and archaeal isoprenoids in a recent marine sediment: Molecular-isotopic evidence for anaerobic oxidation of methane. Geochemistry Geophysics Geosystems 2 (doi:10.1029/2000GC000112).
Diplopterol and 3β-methylbacteriohopanetetrol structures 194
A generalized scheme of a methane seep community 198
Based on Bohrmann, G., and M. E. Torres. 2006. Gas hydrates in marine sediments. In: Schulz, H. D., and M. Zabel, eds., Marine Geochemistry, 2nd ed., Springer (Heidelberg, Germany): 481–512; and Sahling, H., D. Rickert, R. W. Lee, P. Linke, and E. Suess. 2002. Macrofaunal community structure and sulfide flux at gas hydrate deposits from the Cascadia convergent margin, NE Pacific. Marine Ecology Progress Series 231:121–138.
An anaerobic methane-oxidizing microbial consortium 203
After Orphan, V. J., W. Ussler III, T. H. Naehr, C. H. House, K.-U. Hinrichs, and C. K. Paull. 2004. Geological, geochemical, and microbiological heterogeneity of the seafloor around methane vents in the Eel River Basin, off shore California. Chemical Geology 205:265–289.
Biomarkers in methane-rich environments: carbon-13 depletion and suspected source organisms 205
Eel River Basin isotope data: Hinrichs, K.-U., R. E. Summons, V. J. Orphan, S. P. Sylva, and J. M. Hayes. 2000. Molecular and isotopic analysis of anaerobic methane-oxidizing communities in marine sediments. Organic Geochemistry 31:1685–1701; Hinrichs, K.-U., J. M. Hayes, S. P. Sylva, P. G. Brewer, and E. F. DeLong. 1999. Methane-consuming archaebacteria in marine sediments. Nature 398:802–805; and Orphan, V. J., K.-U. Hinrichs, W. Ussler III, C. K. Paull, L. T. Taylor, S. P. Sylva, J. M. Hayes, and E. F. DeLong. 2001. Comparative analysis of methane-oxidizing archaea and sulfate-reducing bacteria in anoxic marine sediments. Applied and Environmental Microbiology 67:1922–1934.
Hydrate Ridge isotope data: Elvert, M., E. Suess, and M. J. Whiticar. 1999. Anaerobic methane oxidation associated with marine gas hydrates: Superlight C-isotopes from saturated and unsaturated C20 and C25 irregular isoprenoids. Naturwissenschaft en 86:295–300; Boetius, A., K. Ravenschlag, C. J. Schubert, D. Rickert, F. Widdel, A. Gieseke, R. Amann, B. B. Jørgensen, U. Witte, and O. Pfannkuche. 2000. A marine microbial consortium apparently mediating anaerobic oxidation of methane. Nature 407:623–626; Elvert, M., A. Boetius, K. Knittel, and B. B. Jørgensen. 2003. Characterization of specific membrane fatty acids as chemotaxonomic markers for sulfate-reducing bacteria involved in anaerobic oxidation of methane. Geomicrobiology Journal 20:403–419; and Elvert, M., E. C. Hopmans, T. Treude, A. Boetius, and E. Suess. 2005. Spatial variations of methanotrophic consortia at cold methane seeps: Implications from a high-resolution molecular and isotopic approach. Geobiology 3:195–209.
Napoli mud volcano isotope data: Pancost, R. D., J. S. Sinninghe Damsté, S. de Lint, M. J. E. C. van der Maarel, and J. C. Gottschal. 2000. Biomarker evidence for widespread anaerobic methane oxidation in Mediterranean sediments by a consortium of methanogenic archaea and bacteria. Applied and Environmental Microbiology 66:1126–1132; and Egorov, A. V., and M. K. Ivanov. 1998. Hydrocarbon gases in sediments and mud breccia from the central and eastern Part of the Mediterranean Ridge. Geo-Marine Letters 18:127–138.
Biomarkers of methanotrophs in ice age sediments from the Santa Barbara Basin: evidence of methane hydrate decomposition? 208
After Hinrichs, K.-U., L. R. Hmelo, and S. P. Sylva. 2003. Molecular fossil record of elevated methane levels in Late Pleistocene coastal waters. Science 299:1214–1217.
Crenarchaeol 215
Tetraether distributions: North Sea versus Arabian Sea 216
After Schouten, S., E. C. Hopmans, E. Schefuß, and J. S. Sinninghe Damsté. 2002. Distributional variations in marine crenarchaeotal membrane lipids: A new tool for reconstructing ancient sea water temperatures. Earth and Planetary Science Letters 204:265–274.
Calibration of the Tetraether Index (TEX86) in surface sediments, 2002 217
After Schouten, S., E. C. Hopmans, E. Schefuß, and J. S. Sinninghe Damsté. 2002. Distributional variations in marine crenarchaeotal membrane lipids: A new tool for reconstructing ancient sea water temperatures. Earth and Planetary Science Letters 204:265–274.
Examples of ladderane lipids from anammox bacteria 222
Elevated levels of 2-methyl hopanoids in Cretaceous black shales: did cyanobacteria take over during oceanic anoxic events? 225
After Kuypers, M. M. M., Y. van Breugel, S. Schouten, E. Erba, and J. S. Sinninghe Damsté. 2004. N2-fixing cyanobacteria supplied nutrient N for Cretaceous oceanic anoxic events. Geology 32:853–856.
Geologic records of oleanane in ancient sediments and fossil plants 231
After Moldowan, J. M., J. Dahl, B. J. Huizinga, F. J. Fago, L. J. Hickey, T. M. Peakman, and D. W. Taylor. 1994. The molecular fossil record of oleanane and its relation to angiosperms. Science 265:768–771.
Evolution and diversification of marine algae: microfossils and molecular fossils 237
After Schwark, L., and P. Empt. 2006. Sterane biomarkers as indicators of Palaeozoic algal evolution and extinction events. Palaeogeography Palaeoclimatology Palaeoecology 240:225–236; and Knoll, A. H., R. E. Summons, J. R. Waldbauer, and J. E. Zumberge. 2007. The geological succession of primary producers in the oceans. In: Falkowski, P., and A. H. Knoll, eds., The Evolution of Primary Producers in the Sea, Elsevier (Amsterdam): 133–163.
Proterozoic versus Phanerozoic organic matter: comparing isotope compositions 248
After Brocks, J. J., R. Buick, R. E. Summons, and G. A. Logan. 2003. A reconstruction of Archean biological diversity based on molecular fossils from the 2.78 to 2.45 billion-year-old Mount Bruce Supergroup, Hamersley Basin, Western Australia. Geochimica et Cosmochimica Acta 67:4321–4335.
Isopropylcholestane 250
Oxygen, ocean chemistry, and life: coevolution 252
Data synthesized from various sources, including Catling, D. C., and M. W. Claire. 2005. How Earth’s atmosphere evolved to an oxic state: A status report. Earth and Planetary Science Letters 237:1–20; Brocks, J. J., R. Buick, R. E. Summons, and G. A. Logan. 2003. A reconstruction of Archean biological diversity based on molecular fossils from the 2.78 to 2.45 billion-year-old Mount Bruce Supergroup, Hamersley Basin, Western Australia. Geochimica et Cosmochimica Acta 67(22):4321–4335; Brocks, J. J., G. D. Love, R. E. Summons, A. H. Knoll, G. A. Logan, and S. A. Bowden. 2005. Biomarker evidence for green and purple sulphur bacteria in a stratified Palaeoproterozoic sea. Nature 437:866–870; Peterson, K. J., R. E. Summons, and P. C. J. Donoghue. 2007. Molecular palaeobiology. Palaeontology 50:775–809; and Roger Summons, personal communication.
Okenone and okenane structures 253
13C-depleted kerogens from the Archean 256
After Brocks, J. J., R. Buick, R. E. Summons, and G. A. Logan. 2003. A reconstruction of Archean biological diversity based on molecular fossils from the 2.78 to 2.45 billion-year-old Mount Bruce Supergroup, Hamersley Basin, Western Australia. Geochimica et Cosmochimica Acta 67:4321–4335.
A biomarker-centric tree of life 256
In this tree, we have included the common names and groupings of organisms that are discussed in Echoes of Life, along with a few familiar groups as reference points, and their characteristic biomarkers. Some of the prokaryote groups, such as sulfate-reducing bacteria and methanotrophs, are turning out to have representatives in phylogenetically disparate branches—we have not tried to represent this on our tree but rather have showed them in the group associated with the illustrated biomarkers. The lengths of the branches do not accurately represent the distances between branch points, but we have attempted to give some conceptual sense of those distances, based on both phylogenetic knowledge and the geologic record.
A synthesis of information presented throughout this book and contained in the bibliography, the tree was initially inspired by Jochen Brocks and Roger Summons. The relative placement of organisms on the tree is based on the best consensus we could find of current phylogenetic knowledge. We also, of course, were constrained by space and format. See, in particular: Brocks, J. J., and R. E. Summons. 2003. Sedimentary hydrocarbons, biomarkers for early life. In: Holland, H. D., and K. K. Turekian, eds., Treatise on Geochemistry, Vol. 8, Biogeochemistry, Elsevier (Amsterdam): 63–115. See also Brocks, J. J., and A. Pearson. 2005. Building the biomarker tree of life. Molecular Geomicrobiology Reviews in Mineralogy and Geochemistry 59:233–258; Pace, N. R. 2001. The universal nature of biochemistry. Proceedings of the National Academy of Sciences 98: 805–808; Pennisi, E. 2003. Drafting a Tree. Science 300: 1694; and the Tree of Life Web Project, http://www.tolweb.org.