The PaleoNet Forum: A Monthly Electronic Journal August, 1995: Volume 1, Issue 1 Quo Vadis Paleontology? Douglas H. Erwin Research Paleobiologist and Curator of Paleozoic Molluscs
Department of Paleobiology, National Museum of Natural History, Smithsonian Institution,
Cloud's view was simply that paleontology is not about "the study of fossils" but the history of life on the earth. Naturally this broad view includes fossils, their systematics, preservation, and sedimentary, geographic, environmental and ecological context, but also encompasses the chemical history of the oceans and atmosphere, records of climatic change, the use of geochronology, sequence stratigraphy and chemostratigraphy to establish correlations and the rates and timing of evolutionary and paleontologic events, and the relationship between tectonic events and the history of life. Early on Cloud recognized the significance of molecular data as a tool (hardly a panacea) for revealing the pattern of historical events: molecular evolution falls within the purview of paleontology as well! I have little doubt that were he were alive, Cloud would recognize the continuing promise of molecular data for deciphering the history of life, and the unique promise of ancient DNA studies to contribute 'molecular fossils' to resolve such questions. Thus a better definition of paleontology might be "the study of the history of Life and the changing environment in which it evolves".
There is a subtle difference between this view of paleontology and the more common view of 'paleobiology'. The research program of paleobiology (exemplified by the journal Paleobiology, of which I become Co-Editor on 1 October, 1995), emphasizes the biologic aspects of the history of life, including quantitative studies of taxonomic and morphologic diversity, simulation and actualistic approaches and phylogenetic (cladistic) analyses. The Tree Of Life Project is one example of this biotic approach. Particularly significant has been a most welcome emphasis on rigorous analysis and testing of paleobiological questions, and on how preservational and sampling problems distort the fossil record. The research program of paleobiology has, as a whole, introduced important new questions and advanced the quality of research tremendously. Indeed, two of the most exciting developments in paleontology fall squarely within the domain of paleobiology:
Developmental Biology and Paleobiology
Lately I have spent as much time delving into the intricacies of homeotic genes (see the Homeobox Page and the UCSF Kenyon Lab Page) and other aspects of developmental biology as I have reading paleontological journals. [Note: No, I am not contemplating a career change!] The explosion of molecular knowledge about the processes of development is having a tremendous impact on our understanding of the evolution of developmental processes. The similarities in developmental processes between the fruit fly Drosophila and vertebrates is remarkable and far closer that anyone would have imagined just a few years ago. For example, the latest issue of Nature to reach my desk (20 July 1995) contains a paper by Holley and others demonstrating that the systems controlling dorso-ventral patterning are shared by Drosophila and vertebrates. This comes soon after the discovery by Quiring and others (1994) that the gene Pax-6 controls eye formation in both Drosophila and vertebrates. So what? Well, developmental biologists are great people, and they produce all sorts of really neat data, but they require organismal biologists to point out that the Pax-6 homology doesn't mean that fly eyes and vertebrate eyes are the same, but that the ancestor of flies and vertebrates probably had a simple eye spot, the formation of which was controlled by Pax-6. And then paleontologists are required to interact with biologists to uncover something about the protostome/deuterostome ancestor, a little worm-like creature burrowing around on the mud in some late Neoproterozoic sea. The critical point here is that the combination of paleontology, comparative biology and molecular developmental biology allows us to not only describe what this animal was like, both morphologically and behaviorally (through trace fossil evidence) but also specify the genes that were active in forming major elements of the body plan.
Integrated Comparative Studies
Paleontology may well have more data to handle than geophysics. Think about it: specimens at localities, stratigraphic data, and geographic ranges are nothing compared with the information contained in the shape of a specimen. Unfortunately, paleontology seems to attract people like me, with the quantitative ability of a snail; consequently we have been slow to fully exploit this information. Instead, we have tended to rely upon taxic information (data about the stratigraphic ranges of taxa) as a proxy for patterns of morphologic change. Fortunately, there is a growing host of morphometriticans who have developed a host of tools for the quantitative analysis of shape (see the SUNY Stony Brook Morphometrics Page). These powerful tools are finally allowing description of the patterns of mophological evolution within major groups. Mike Foote's work, largely published in Paleobiology is perhaps the best example of such studies. Yet to me the full power of these approaches has yet to be realized, for a true understanding of morphologic evolution demands that such studies be considered within a rigorous phylogenetic framework (e.g., the Tree Of Life Project and UC Berkeley's Phylogeny of Life Page). Only then can we see the morphologic transitions between ancestor and descendent and begin to consider the evolutionary processes behind the patterns, including phylogenetic constraints, patterns of functional evolution and the like. Both morphometric and phylogenetic studies are solid contributions in and of themselves, but together they provide a much more powerful entryway into evolutionary history.
As exciting as these developments are, the full power of the addition of developmental studies to paleobiology, or the incorporation of phylogenetic and morphometric tools comes from using them to understand specific events. Research on the late Neoproterozoic and Cambrian provides a wonderful example of this. The explosive evolution of life during this Cambrian radiation marks it as one of the most significant events in the history of life, and one of the most puzzling. As noted above, developmental biology has provided a range of exciting new insights into these events, and new phylogenetic and morphometric analyses have explored many of the evolutionary patterns. Yet fully understanding this event requires integration of considerable geologic information. Here the Neoproterozoic Working Group, under the auspices of the International Geological Correlation Programme (IGCP) has led the way in developing a refined, global stratigraphic framework. This framework is based on fossil, geochemical, sequence stratigraphic and geochronologic evidence, and has allowed the integration of considerable evolutionary and geochemical information. This project, and earlier efforts on the Cambrian boundary enabled many geologists to visit many of the important sections around the world, stimulating considerable research far removed from the 'primary' goal of defining boundary sections. Individual members of the project may be more interested in stratigraphic correlation, sequence stratigraphy or fossils, but their combined efforts are generating insights which promise to revolutionize our views of this interval. Contrast this with the recent efforts of the Permo-Triassic boundary working group, also sponsored by IGCP. Here the efforts have focused more narrowly on defining the Permo-Triassic boundary, correlating between sections and picking a global stratotype section and point (GSSP). The efforts have been important, but no integrated research effort has emerged and the potential for increased understanding of the nature of the extinction has been lost.
These examples demonstrate the power of a truly synthetic paleontology: a field which integrates both biology and geology to solve the riddles of the history of life. Despite the loss of portions and funding which many of us have been lamenting of late (particularly on PaleoNet), I see a tremendously bright future for paleontology. But in my view our future lies with Preston Cloud's broadly synthetic view of our field, of paleontologists as the true historians of life on the earth.
Holley, S. A., Jackson, P. D., Sasai, Y., Lu, B., De Robertis, E. M., Hoffmann, F. M., and Ferguson, E. L., 1995, A conserved system for dorso-ventral patterning in insects and vertebrates involving sog and chordin: Nature, v. 376, pp. 249-253.
Quiring, R., Walldorf, U., Kloter, U., and Gehring, W. J., 1994. Homology of the eyeless gene of Drosophila to the smalleye gene in mice and Aniridia in humans: Science, v. 265, pp. 785-789.