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The hierarchical structure of organisms: a scale and documentation of a trend in the maximum

Published online by Cambridge University Press:  08 February 2016

Daniel. W. McShea
Daniel. W. McShea*
Affiliation:
Department of Biology, Duke University, Box 90338, Durham, North Carolina 27708-0338. E-mail: dmcshea@duke.edu
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Abstract

The degree of hierarchical structure of organisms—the number of levels of nesting of lower-level entities within higher-level individuals—has apparently increased a number of times in the history of life, notably in the origin of the eukaryotic cell from an association of prokaryotic cells, of multicellular organisms from clones of eukaryotic cells, and of integrated colonies from aggregates of multicellular individuals. Arranged in order of first occurrence, these three transitions suggest a trend, in particular a trend in the maximum, or an increase in the degree of hierarchical structure present in the hierarchically deepest organism on Earth. However, no rigorous documentation of such a trend—based on operational and consistent criteria for hierarchical levels—has been attempted. Also, the trajectory of increase has not been examined in any detail. One limitation is that no hierarchy scale has been developed with sufficient resolution to document more than these three major increases. Here, a higher-resolution scale is proposed in which hierarchical structure is decomposed into levels and sublevels, with levels reflecting number of layers of nestedness, and sublevels reflecting degree of individuation at the highest level. The scale is then used, together with the body-fossil record, to plot the trajectory of the maximum. Two alternative interpretations of the record are considered, and both reveal a long-term trend extending from the Archean through the early Phanerozoic. In one, the pattern of increase was incremental, with almost all sublevels arising precisely in order. The data also raise the possibility that waiting times for transitions between sublevels may have decreased with increasing hierarchical level (and with time). These last two findings—incremental increase in level and decreasing waiting times—are tentative, pending a study of possible biases in the fossil record.

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Paleobiology , Volume 27 , Issue 2 , Spring 2001 , pp. 405 - 423
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Copyright © The Paleontological Society 

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References

Literature Cited

Allen, T. F. H., and Starr, T. B. 1982. Hierarchy: perspectives for ecological complexity. University of Chicago Press, Chicago.Google Scholar
Amard, B., and Bertrand-Sarfati, J. 1997. Microfossils in 2000 Ma old cherty stromatolites of the Franceville Group, Gabon. Precambrian Research 81:197–221.CrossRefGoogle Scholar
Anderson, C., and McShea, D. W.In press. Individual versus social complexity, with particular reference to ant colonies. Biological Reviews.Google Scholar
Arthur, W. 1997. The origin of animal body plans. Cambridge University Press, Cambridge.CrossRefGoogle Scholar
Banta, W. C., McKinney, F. K., and Zimmer, R. L. 1974. Bryozoan monticules: excurrent water outlets? Science 185:783–784.CrossRefGoogle ScholarPubMed
Beklemishev, W. N. 1969. Principles of comparative anatomy of invertebrates, Vol. I. Promorphology. Kabata, Z., ed. (MacLennan, J. M., transl.). University of Chicago Press, Chicago.Google Scholar
Bell, G., and Mooers, A. O. 1997. Size and complexity among multicellular organisms. Biological Journal of the Linnean Society 60:345–363.CrossRefGoogle Scholar
Bengtson, S., ed. 1994. Early life on Earth (Nobel Symposium No. 84). Columbia University Press, New York.Google Scholar
Berry, W. B. N. 1987. Phylum Hemichordata (including Graptolithina). Pp. 612–636in Boardman, R. S., Cheetham, A. H., and Rowell, A. J., eds. Fossil invertebrates. Blackwell Scientific, Palo Alto, Calif.Google Scholar
Boardman, R. S., and Cheetham, A. H. 1973. Degrees of colony dominance in stenolaemate and gymnolaemate bryozoa. Pp. 121–220in Boardman, R. S., et al. 1973.Google Scholar
Boardman, R. S., and Cheetham, A. H. 1987. Phylum Bryozoa. Pp. 497–549in Boardman, R. S., Cheetham, A. H., and Rowell, A. J., eds. Fossil invertebrates. Blackwell Scientific, Palo Alto, Calif.Google Scholar
Boardman, R. S., Cheetham, A. H., and Oliver, W. A. Jr., eds. 1993. Animal colonies: development and function through time. Dowden, Hutchinson, and Ross, Stroudsburg, Penn.Google Scholar
Bonner, J. T. 1988. The evolution of complexity. Princeton University Press, Princeton, N.J.Google Scholar
Bonner, J. T. 1998. The origins of multicellularity. Integrative Biology 1:27–36.3.0.CO;2-6>CrossRefGoogle Scholar
Bowring, S. A., and Erwin, D. H. 1998. A new look at evolutionary rates in deep time: uniting paleontology and high-precision geochronology. GSA Today 8:1–8.Google Scholar
Brandon, R. N. 1996. Concepts and methods in evolutionary biology. Cambridge University Press, Cambridge.Google Scholar
Brandon, R. N. 1999. The units of selection revisited: the modules of selection. Biology and Philosophy 14:167–180.CrossRefGoogle Scholar
Brocks, J. J., Logan, G. A., Buick, R., and Summons, R. E. 1999. Archean molecular fossils and the early rise of eukaryotes. Science 285:1033–1036.CrossRefGoogle ScholarPubMed
Bulman, O. M. B. 1970. Graptolithina. Part V of Teichert, C., ed. Treatise on invertebrate paleontology. Geological Society of America and University of Kansas, Boulder, Colo.Google Scholar
Bunge, M. 1959. Levels: a semantical preliminary. Review of Metaphysics 13:396–400.Google Scholar
Buss, L. W. 1987. The evolution of individuality. Princeton University Press, Princeton, N.J.Google Scholar
Butterfield, N. J. 2000. Bangiomorpha pubsscens n. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes. Paleobiology 26:386–404.2.0.CO;2>CrossRefGoogle Scholar
Butterfield, N. J., Knoll, A. H., and Swett, K. 1990. A bangiophyte red alga from the Proterozoic of Arctic Canada. Science 250:104–107.CrossRefGoogle ScholarPubMed
Butterfield, N. J., Knoll, A. H., and Swett, K. 1994. Paleobiology of the Neoproterozoic Svanbergfjellet Formation, Spitsbergen. Fossils and Strata 34:1–84.CrossRefGoogle Scholar
Campbell, D. T. 1958. Common fate, similarity, and other indices of the status of aggregates of persons as social entities. Behavioral Sciences 3:14–25.CrossRefGoogle Scholar
Cisne, J. L. 1974. Evolution of the world fauna of aquatic free-living arthropods. Evolution 28:337–366.CrossRefGoogle ScholarPubMed
Cloud, P. 1986. Reflections on the beginnings of metazoan evolution. Precambrian Research 31:405–408.CrossRefGoogle Scholar
Coates, A. G., and Oliver, W. A. Jr. 1973. Coloniality in zoantharian corals. Pp. 3–27in Boardman, et al. 1973.Google Scholar
Morris, S. Conway 1993. Ediacaran-like fossils in Cambrian Burgess Shale-type faunas of North America. Palaeontology 36:593–635.Google Scholar
Cook, P. L. 1979. Some problems in interpretation of heteromorphy and colony integration in Bryozoa. In Larwood, G. P. and Rosen, B. R., eds. Biology and systematics of colonial organisms. Systematics Association Special Volume 11:193–210. Academic Press, London.Google Scholar
Corning, P. A. 1983. The synergism hypothesis: a theory of progressive evolution. McGraw-Hill, New York.Google Scholar
Corning, P. A. 1997. Holistic Darwinism: ‘synergistic selection’ and the evolutionary process. Journal of Social and Evolutionary Systems 20:363–401.Google Scholar
Debrenne, F. M., Gangloff, R. A., and Lafuste, J. G. 1987. Tabulaconus Handfield: Microstructure and its implication in the taxonomy of primitive corals. Journal of Paleontology 61:1–9.CrossRefGoogle Scholar
Delwiche, C. F. 1999. Tracing the thread of plastid diversity through the tapestry of life. American Naturalist 154(Suppl.):S164–S177.CrossRefGoogle ScholarPubMed
Dewel, R. A. 2000. Colonial origin for Eumetazoa: major morphological transitions and the origin of bilaterian complexity. Journal of Morphology 243:35–74.3.0.CO;2-#>CrossRefGoogle ScholarPubMed
Eldredge, N., and Salthe, S. N. 1984. Hierarchy and evolution. Oxford Surveys in Evolutionary Biology 1:184–208.Google Scholar
Fiebleman, J. K. 1955. Theory of integrative levels. British Journal for the Philosophy of Science 5:59–66.CrossRefGoogle Scholar
Ghiselin, M. T. 1997. Metaphysics and the origin of species. State University of New York Press, Albany.Google Scholar
Glaessner, M. F. 1987. Discussion about some ‘worm-like’ fossils. Precambrian Research 36:353–355.CrossRefGoogle Scholar
Glaessner, M. F., and Wade, M. 1966. The late Precambrian fossils from Ediacara, South Australia. Palaeontology 9:599–628.Google Scholar
Golubic, S., Sergeev, V. N., and Knoll, A. H. 1995. Mesoproterozoic Archaeoellipsoides: akinetes of heterocystous cyanobacteria. Lethaia 28:285–298.CrossRefGoogle ScholarPubMed
Gould, S. J. 1996. Full house: the spread of excellence from Plato to Darwin. Harmony Books, New York.CrossRefGoogle Scholar
Gould, S. J., and Lloyd, E. A. 1999. Individuality and adaptation across levels of selection: how shall we name and generalize the unit of Darwinism. Proceedings of the National Academy of Sciences USA 96:11904–11909.CrossRefGoogle Scholar
Grey, K., and Williams, I. R. 1990. Problematic bedding-plane markings from the Middle Proterozoic Manganese Subgroup, Bangemall Basin, Western Australia. Precambrian Research 46:307–327.CrossRefGoogle Scholar
Grotzinger, J. P., Bowring, S. A., Saylor, B. Z., and Kaufman, A. J. 1995. Biostratigraphic and geochronologic constraints on early animal evolution. Science 270:598–604.CrossRefGoogle Scholar
Han, T.-M., and Runnegar, B. 1992. Megascopic eukaryotic algae from the 2.1-billion-year-old Negaunee Iron-Formation, Michigan. Science 257:232–235.CrossRefGoogle ScholarPubMed
Handfield, R. C. 1969. Early Cambrian coral-like fossils from the Northern Cordillera of Western Canada. Canadian Journal of Earth Sciences 6:782–785.CrossRefGoogle Scholar
Hartman, W. D., and Reiswig, H. M. 1973. The individuality of sponges. Pp. 567–584in Boardman, et al. 1973.Google Scholar
Heylighen, F. 1999. The growth of structural and functional complexity during evolution. Pp. 17–44in Heylighen, F., Bollen, J., and Riegler, A., eds. The evolution of complexity: the violet book of “Einstein meets Magritte.” Kluwer Academic, Dordrecht.Google Scholar
Hofmann, H. J. 1988. An alternative interpretation of the Ediacaran (Precambrian) chondrophore Chondroplon Wade. Alcheringa 12:315–318.CrossRefGoogle Scholar
Hofmann, H. J. 1994. Proterozoic carbonaceous compressions (“metaphytes” and “worms”). Pp. 342–357in Bengtson, 1994.Google Scholar
Hofmann, H. J., Narbonne, G. M., and Aitken, J. D. 1990. Ediacaran remains from the intertillite beds in northwestern Canada. Geology 18:1199–1202.2.3.CO;2>CrossRefGoogle Scholar
Horodyski, R. J. 1982. Problematic bedding-plane markings from the Middle Proterozoic Appekunny Argillite, Belt Supergroup, Northwestern Montana. Journal of Paleontology 56:882–889.Google Scholar
Horodyski, R. J. 1992. The Middle Proterozoic—a time of experimentation in megascopic life. Geological Society of America Abstracts with Programs 24:A99.Google Scholar
Hull, D. L. 1980. Individuality and selection. Annual Review of Ecology and Systematics 11:311–332.CrossRefGoogle Scholar
Hyman, L. H. 1940. The invertebrates: Protozoa through Ctenophora. McGraw-Hill, New York.Google Scholar
Jenkins, R. F. 1984. Interpreting the oldest fossil cnidarians. Palaeontographica American 54:95–104.Google Scholar
Jenkins, R. F. 1985. The enigmatic Ediacaran (late Precambrian) genus Rangea and related forms. Paleobiology 11:336–355.CrossRefGoogle Scholar
Jenkins, R. F. 1992. Functional and ecological aspects of Ediacaran assemblages. Pp. 131–176in Lipps, J. H. and Signor, P. W., eds. Origin and early evolution of the Metazoa. Plenum, New York.CrossRefGoogle Scholar
Jenkins, R. F., and Gehling, J. G. 1978. A review of the frond-like fossils of the Ediacara assemblage. Records of the South Australia Museum 17:347–359.Google Scholar
Kah, L. C., Sherman, A. G., Narbonne, G. M., Knoll, A. H., and Kaufman, A. J. 1999. 13C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations. Canadian Journal of Earth Sciences 36:313–332.CrossRefGoogle Scholar
Kaiser, J. A., and Losick, R. 1993. How and why bacteria talk to each other. Cell 73:873–885.CrossRefGoogle ScholarPubMed
Keller, L., ed. 1999. Levels of selection in evolution. Princeton University Press, Princeton, N.J.Google Scholar
Kirk, D. L. 1998. Volvox: molecular-genetic origins of multicellularity and cellular differentiation. Cambridge University Press, Cambridge.Google Scholar
Knoll, A. H. 1992. The early evolution of eukaryotes: A geological perspective. Science 256:622–627.CrossRefGoogle ScholarPubMed
Knoll, A. H., and Bambach, R. K. 2000. Directionality in the history of life: diffusion from the left wall or repeated scaling of the right. Pp. xxx–xxxin Erwin, D. H. and Wing, Scott L.Deep time: Paleobiology's perspective. Paleobiology 26(Suppl. to No. 4).Google Scholar
Leigh, E. G. Jr. 1983. When does the good of the group override the advantage of the individual? Proceedings of the National Academy of Sciences USA 80:2985–2989.CrossRefGoogle Scholar
Leigh, E. G. Jr. 1991. Genes, bees and ecosystems: the evolution of a common interest among individuals. Trends in Ecology and Evolution 6:257–262.CrossRefGoogle ScholarPubMed
Li, C.-W., Chen, J.-Y., and Hua, T.-E. 1998. Precambrian sponges with cellular structures. Science 279:879–882.CrossRefGoogle ScholarPubMed
Lidgard, S. 1985. Zooid and colony growth in encrusting bryozoans. Palaeontology 28:255–291.Google Scholar
Lidgard, S. 1986. Ontogeny in animal colonies: a persistent trend in the bryozoan fossil record. Science 232:230–232.CrossRefGoogle ScholarPubMed
Lidgard, S., and Jackson, J. B. C. 1989. Growth in encrusting cheilostome bryozoans: I. Evolutionary trends. Paleobiology 15:255–282.CrossRefGoogle Scholar
MacMahon, J. A., Phillips, D. L., Robinson, J. V., and Schimpf, D. J. 1978. Levels of biological organization: an organism-centered approach. Bioscience 28:700–704.CrossRefGoogle ScholarPubMed
Smith, J. Maynard 1988. Evolutionary progress and levels of selection. Pp. 219–230in Nitecki, M. H., ed. Evolutionary progress. University of Chicago Press, Chicago.Google Scholar
Smith, J. Maynard, and Szathmáry, E. 1995. The major transitions in evolution. W. H. Freeman, Oxford.Google Scholar
Smith, J. Maynard, and Szathmáry, E. 1999. The origins of life. Oxford University Press, Oxford.CrossRefGoogle Scholar
McShea, D. W. 1993. Evolutionary change in the morphological complexity of the mammalian vertebral column. Evolution 47:730–740.CrossRefGoogle ScholarPubMed
McShea, D. W. 1994. Mechanisms of large-scale trends. Evolution 48:1747–1763.CrossRefGoogle Scholar
McShea, D. W. 1996a. Metazoan complexity and evolution: is there a trend? Evolution 50:477–492.Google ScholarPubMed
McShea, D. W. 1996b. Complexity and homoplasy. Pp. 207–225in Sanderson, M. J. and Hufford, L., eds. Homoplasy: the recurrence of similarity in evolution. Academic Press, San Diego.CrossRefGoogle Scholar
McShea, D. W. 1998. Possible largest-scale trends in organismal evolution: eight “live hypotheses.” Annual Review of Ecology and Systematics 29:293–318.CrossRefGoogle Scholar
McShea, D. W. 2000. Sense and depth. Biology and Philosophy 15:751–758.CrossRefGoogle Scholar
McShea, D. W.In press. Parts and integration: the consequences of hierarchy. In McKinney, F. K., Lidgard, S., and Jackson, J. B. C., eds. Process from pattern in the fossil record. University of Chicago Press, Chicago.Google Scholar
McShea, D. W., and Venit, E. P. 2001. What is a part? Pp. 259–284in Wagner, G. P., ed. The character concept in volutionary biology. Academic Press, San Diego.CrossRefGoogle Scholar
McShea, D. W., Venit, E. P., and Simon, V. 1999. Hierarchical complexity of organisms: dynamics of a well-known trend. Geological Society of America Abstracts with Programs 31:A171.Google Scholar
Michod, R. E. 1999. Darwinian dynamics: evolutionary transitions in fitness and individuality. Princeton University Press, Princeton, N.J.Google Scholar
Mishler, B. D., and Brandon, R. N. 1987. Individuality, pluralism, and the phylogenetic species concept. Biology and Philosophy 2:397–414.CrossRefGoogle Scholar
Narbonne, G. M., Kaufman, A. J., and Knoll, A. H. 1994. Integrated chemostratigraphy and biostratigraphy of the Windermere Supergroup, northwestern Canada: implications for Neoproterozoic correlations and the early evolution of animals. Geological Society of America Bulletin 106:1281–1292.2.3.CO;2>CrossRefGoogle ScholarPubMed
Needham, J. 1943. Integrative levels: a revaluation of the idea of progress. Pp. 233–272in Needham, J., ed. Time: the refreshing river. Allen and Unwin, London.Google Scholar
Norris, R. D. 1989. Cnidarian taphonomy and affinities of the Ediacara biota. Lethaia 22:381–393.CrossRefGoogle Scholar
Novikoff, A. B. 1945. The concept of integrative levels and biology. Science 101:209–215.CrossRefGoogle ScholarPubMed
Pattee, H. H. 1970. The problem of biological hierarchy. Pp. 117–136in Waddington, C. H., ed. Towards a theoretical biology, Vol. 3. Edinburgh University Press, Edinburgh.Google Scholar
Pettersson, M. 1996. Complexity and evolution. Cambridge University Press, Cambridge.CrossRefGoogle Scholar
Piper, J. D. A., and Zhang, Q. R. 1997. Palaeomagnetism of Neoproterozoic glacial rocks of Huabei Shield: the North China block in Gondwana. Tectonophysics 283:145–171.CrossRefGoogle Scholar
Polanyi, M. 1968. Life's irreducible structure. Science 160:1308–1312.CrossRefGoogle ScholarPubMed
Porter, S. M., and Knoll, A. H. 2000. Testate amoebae in the Neoproterozoic Era: evidence from vase-shaped microfossils in the Chuar Group, Grand Canyon. Paleobiology 26:360–385.2.0.CO;2>CrossRefGoogle Scholar
Raff, R. A. 1996. The shape of life. University of Chicago Press, Chicago.CrossRefGoogle Scholar
Rainbird, R. H., Stern, R. A., Khudoley, A. K., Kropachev, A. P., Heaman, L. M., and Sukhorukow, V. I. 1998. U-Pb geochronology of Riphean sandstone and gabbro from southeast Siberia and its bearing on the Laurentia-Siberia connection. Earth and Planetary Science Letters 164:409–420.CrossRefGoogle Scholar
Redfield, R., ed. 1942. Levels of Integration in Biological and Social Systems. Cattell, Lancaster, Penn.Google Scholar
Rickards, R. B. 1979. Early evolution of graptolites and related groups. Pp. 435–441in House, M. R., ed. The origin of major invertebrate groups. Academic Press, London.Google Scholar
Runnegar, B. 1994. Proterozoic eukaryotes: evidence from biology and geology. Pp. 287–297in Bengtson, 1994.Google Scholar
Salthe, S. N. 1985. Evolving hierarchical systems. Columbia University Press, New York.CrossRefGoogle Scholar
Salthe, S. N. 1993. Development and evolution. MIT Press, Cambridge.CrossRefGoogle Scholar
Savarese, M., Mount, J. F., Sorauf, J. E., and Bucklin, L. 1993. Paleobiologic and paleoenvironmental context of coral-bearing Early Cambrian reefs: implications for Phanerozoic reef development. Geology 21:917–920.2.3.CO;2>CrossRefGoogle Scholar
Schopf, J. W. 1992a. Paleobiology of the Archean. Pp. 25–39in Schopf, J. W. and Klein, C., eds. The Proterozoic biosphere: a multidisciplinary study. Cambridge University Press, Cambridge.CrossRefGoogle Scholar
Schopf, J. W. 1992b. The oldest fossils and what they mean. Pp. 29–63in Schopf, J. W., ed. Major events in the history of life. Jones and Bartlett, Boston.Google Scholar
Schopf, J. W. 1993. Microfossils of the early Archean apex chert: new evidence of the antiquity of life. Science 260:640–646.CrossRefGoogle ScholarPubMed
Schopf, J. W., and Packer, B. M. 1987. Early Archean (3.3-billion to 3.5-billion-year-old) microfossils from Warrawoona Group, Australia. Science 237:70–73.CrossRefGoogle ScholarPubMed
Schopf, J. W., and Walter, M. R. 1983. Archean microfossils: new evidence of ancient microbes. Pp. 214–239in Schopf, J. W., ed. Earth's earliest biosphere: its origin and evolution. Princeton University Press, Princeton, N.J.Google Scholar
Scrutton, C. T. 1997. The Paleozoic corals, I: origins and relationships. Proceedings of the Yorkshire Geological Society 51:177–208.CrossRefGoogle Scholar
Seilacher, A. 1989. Vendozoa: organismic construction in the Proterozoic biosphere. Lethaia 22:229–239.CrossRefGoogle Scholar
Seilacher, A. 1992. Vendobionta and Psammocorallia: lost constructions of Precambrian evolution. Journal of the Geological Society, London 149:607–613.CrossRefGoogle Scholar
Simon, H. A. 1962. The architecture of complexity. Proceedings of the American Philosophical Society 106:467–482.Google Scholar
Simpson, T. L. 1973. Coloniality among the Porifera. Pp. 549–565in Boardman, et al. 1973.Google Scholar
Sober, E., and Wilson, D. S. 1994. A critical review of the philosophical work on the units of selection problem. Philosophy of Science 61:534–555.CrossRefGoogle Scholar
Sorauf, J. E., and Savarese, M. 1995. A Lower Cambrian coral from South Australia. Palaeontology 38:757–770.Google Scholar
Spencer, H. 1900. The principles of biology. Appleton, New York.Google Scholar
Spencer, H. 1904. First principles. J. A. Hill, New York.Google Scholar
Stanley, G. D. Jr. 1986. Chondrophorine hydrozoans as problematic fossils. Pp. 68–86in Hoffman, A. and Nitecki, M. H., eds. Problematic fossil taxa. Oxford University Press, New York.Google Scholar
Stebbins, G. L. 1969. The basis of progressive evolution. University of North Carolina Press, Chapel Hill.Google Scholar
Sterelny, K. 1999. Bacteria at the high table. Biology and Philosophy 14:459–470.CrossRefGoogle Scholar
Sterelny, K., and Griffiths, P. E. 1999. Sex and death: an introduction to the philosophy of biology. University of Chicago Press, Chicago.CrossRefGoogle Scholar
Sun, W. 1986. Are there pre-Ediacaran metazoans? Precambrian Research 31:409–410.Google Scholar
Sun, W. 1987. Discussions on the age of the Liulaobei Formation. Precambrian Research 36:349–352.Google Scholar
Sun, W. 1994. Early multicellular fossils. Pp. 358–369in Bengtson, 1994.Google Scholar
Sun, W., Wang, G., and Zhou, B. 1986. Macroscopic worm-like body fossils from the Upper Precambrian (900–700 Ma), Huainan District, Anhui, China and their stratigraphic and evolutionary significance. Precambrian Research 31:377–403.Google Scholar
Swenson, R., and Turvey, M. T. 1991. Thermodynamic reasons for perception-action cycles. Ecological Psychology 3:317–348.CrossRefGoogle Scholar
Szathmáry, E., and Smith, J. Maynard 1995. The major evolutionary transitions. Nature 374:227–232.CrossRefGoogle ScholarPubMed
Taylor, P. D. 1999. Bryozoans. Pp 623–646in Savazzi, E., ed. Functional morphology of the invertebrate skeleton. Wiley, New York.Google Scholar
Taylor, P. D., and Wilson, M. A. 1999. Dianulites Eichwald, 1829: an unusual Ordovician bryozoan with a high-magnesium calcite skeleton. Journal of Paleontology 73:38–48.CrossRefGoogle Scholar
Valentine, J. W., and May, C. L. 1996. Hierarchies in biology and paleontology. Paleobiology 22:23–33.CrossRefGoogle Scholar
Valentine, J. W., Collins, A. G., and Meyer, C. P. 1994. Morphological complexity increase in metazoans. Paleobiology 20:131–142.CrossRefGoogle Scholar
Vidal, G., and Owska, M. Moczyd 1987. Further reflections on metazoan evolution. Precambrian Research 36:345–348.CrossRefGoogle Scholar
Wade, M. 1971. Bilateral Precambrian chondrophores from the Ediacara Fauna, South Australia. Proceedings of the Royal Society of Victoria 84:183–188.Google Scholar
Wade, M. 1972. Hydrozoa and Scyphozoa and other medusoids from the Precambrian Ediacara Fauna, South Australia. Palaeontology 15:197–225.Google Scholar
Wagner, G. P., and Laubichler, M. D. 2000. Character identification in evolutionary biology: the role of the organism. Theory in Biosciences 119:20–40.CrossRefGoogle Scholar
Walsh, M. M. 1992. Microfossils and possible microfossils from the Early Archean Onverwacht Group, Barberton Mountain Land, South Africa. Precambrian Research 54:271–293.CrossRefGoogle ScholarPubMed
Walsh, M. M., and Lowe, D. R. 1985. Filamentous microfossils from the 3,500-Myr-old Onverwacht Group, Barberton Mountain Land, South Africa. Nature 314:530–532.CrossRefGoogle Scholar
Wimsatt, W. C. 1974. Complexity and organization. Pp. 67–86in Schaffner, K. F. and Cohen, R. S., eds. Philosophy of Science Association 1972. D. Reidel, Dordrecht, Netherlands.Google Scholar
Wimsatt, W. C. 1976. Reductionism, levels of organization, and the mind-body problem. Pp. 205–267in Globus, G. G., Maxwell, G., and Savodnik, I., eds. Consciousness and the brain. Plenum, New York.CrossRefGoogle Scholar
Wimsatt, W. C. 1994. The ontology of complex systems: levels of organization, perspectives, and causal thickets. Canadian Journal of Philosophy, Supplementary Volume 20:207–274.CrossRefGoogle Scholar
Woods, K. N., Knoll, A. H., and German, T. 1998. Xanthophyte algae from the Mesoproterozoic/Neoproterozoic transition: Confirmation and evolutionary implications. Geological Society of America Abstracts with Programs 30:A232.Google Scholar
Wray, G. A., Levinton, J. S., and Shapiro, L. H. 1996. Molecular evidence for deep pre-Cambrian divergences among metazoan phyla. Science 274:568–573.CrossRefGoogle Scholar
Wright, R. 2000. Nonzero: the logic of human destiny. Pantheon, New York.Google Scholar
Xiao, S., Zhang, Y., and Knoll, A. H. 1998. Three-dimensional preservation of algae and animal embryos in a Neoproterozoic phosphorite. Nature 391:553–558.CrossRefGoogle Scholar
Yochelson, E. L., Fedonkin, M. A., and Horodyski, R. A. 1993. Evidence of life in the Appekunny Formation (1.2–1.4 BY), Glacier National Park, Montana. Geological Society of America Abstracts with Programs 25:A268.Google Scholar
Zhang, Y. 1989. Multicellular thallophytes with differentiated tissues from Late Proterozoic phosphate rocks of South China. Lethaia 22:113–132.Google Scholar
Zhang, Y., and Yuan, X. 1992. New data on multicellular thallophytes and fragments of cellular tissues from Late Proterozoic phosphate rocks, South China. Lethaia 25:1–18.Google Scholar
Zhang, Z. 1986. Clastic facies microfossils from the Chuanlinggou Formation (1800 Ma) near Jixian, North China. Journal of Micropalaeontology 5:9–16.Google Scholar
Zhu, S., and Chen, H. 1995. Megascopic multicellular organisms from the 1700-million-year-old Tuanshanzi Formation in the Jixian area, North China. Science 270:620–622.Google Scholar