Geotimes — December 2005 — Out of the Past and Into the Future

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Out of the Past and Into the Future
Douglas H. Erwin

Top paleontology news 2005

Astronomers have observed that our sun lives in a rather boring and uninteresting part of the galaxy, far from the excitement of the galactic core and lacking even the interest of a double star. Paleontologists might also view today as a rather boring and uninteresting interval of geologic history, missing the peculiarities of widespread continental seas, recent massive continental lava flows or rapid bursts of evolutionary change. The recent glaciations and the expansion of a group of highly encephalized primates (us!) aside, the last several million years lack the drama and peculiarities of the more distant geologic past. But the fossil record — now including a rapidly expanding compendium of traditional fossils, as well as molecular biomarkers and isotopic measurements — provides the only reliable account of how life has responded to the challenges and opportunities of past environments.

Paleontology began as a largely descriptive science, using fossils to describe the diversity of past life, establish correlations and relationships between distant areas, and help infer the nature of the environment where the fossils were entombed. By the late 1960s, a new generation of researchers established a fresh intellectual framework for the field, generally termed paleobiology. The lead in this new enterprise was taken by Norman Newell of the American Museum of Natural History, a true giant of the field, who passed away earlier this year.

Some of the greatest recent triumphs of paleontology have come from ... intensive and rewarding collaborations among paleontologists, stratigraphers, geochemists and geochronologists.

Later, Jim Valentine, David Raup and eventually Steve Stanley, Richard Bambach and the late Jack Sepkoski and Steven Jay Gould, among others, began to ask new questions about the diversity of life through time: What are the patterns in the fossil record? How important were mass extinctions in changing patterns of animal and plant diversity? Are traditional views of evolutionary processes sufficient to explain the diversity of patterns recorded in the fossil record, or does the fossil record suggest that new evolutionary processes must have occurred?

Over the past 25 years, research in paleobiology has produced new techniques for understanding the quality of the fossil record, correcting for preservation differences, rigorously describing the evolutionary tree of life through phylogenetic analysis, and generating new means of quantifying changes in form (morphology). Sequence stratigraphy has been incorporated into paleontological thinking, revealing that the layered architecture of sediments can have a significant impact on apparent patterns of fossil abundance.

Among the most encouraging recent developments is a large-scale collaborative effort, led by John Alroy, Charles Marshall and Arnie Miller, known as the PaleoDatabase Project. Dozens of paleontologists from around the world have been constructing a massive record of fossil occurrences to test whether a more rigorous statistical sampling of the paleontological literature can verify Sepkoski’s now accepted patterns of marine fossil diversity over the past 600 million years, and new results from this effort can be expected soon. Controversy continues to surround this project, particularly over how large a trawl of the literature is needed and whether a literature-based approach is even sufficient, or if a more intensive, field-based approaches are required. Still, the database project represents a much-needed step toward a community-wide, geoinformatics approach.

One of the criticisms leveled at such studies of taxonomic diversity, however, is the lack of sufficient environmental context. Yet some of the greatest recent triumphs of paleontology have come from just such studies, generally involving intensive and rewarding collaborations among paleontologists, stratigraphers, geochemists and geochronologists. The premier example is doubtlessly the study of the causes and consequences of the end-Cretaceous mass extinction and the generally accepted demonstration that an extraterrestrial object was responsible for the event, which led to the demise of the dinosaurs.

In the past few years, the emphasis in extinction research has changed to the Permian/Triassic mass extinction of 251 million years ago. This year, researchers further established that this greatest of all mass extinctions occurred in less than 500,000 years and was evidently closely associated with the eruption of one of the largest continental flood basalts of the time (see story, this issue).

Some of the most exciting research recently has focused on the diversification of animals that occurred 545 million years ago, called the Cambrian Explosion. Recent studies of the Cambrian continue to describe new finds but now also include detailed descriptions of early Cambrian food webs. Paleontologists have also integrated estimates of the origin of various animal groups based on molecular DNA clocks with an array of late Precambrian (540 to 800 million years ago) microfossil data to better understand the new feeding styles, enabled by the origin of the animal gut and nervous system. Equally important has been trying to understand the relationship between this extraordinary burst of evolutionary novelty and such environmental changes as the several late Neoproterozioc glaciations, the end of sulfur-rich oceans, and an increase in atmospheric oxygen.

Paleontologists, however, have been remiss in developing testable, quantitative, process-based models of evolutionary and ecological mechanisms on the temporal and spatial scale for the sort of data we can collect from the fossil record. The next opportunities for significant advances in paleontology will come from such modeling.

Critical to this effort will be establishing how to test these process models using data from the rock record. This sort of approach is already starting to emerge, and as the techniques spread more widely, they promise to radically restructure both how paleontologists work and, far more importantly, our understanding of the history of life.

Erwin is a senior scientist at the Smithsonian Institution’s National Museum of Natural History and a part-time research professor at the Santa Fe Institute. E-mail: erwind@si.edu.

Links:
"The 'Great Dying'debate," Geotimes, December 2005.
"Norman Newell: Legendary and versatile," Geotimes, January 2005.
PaleoDatabase

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