Magazine article Insight on the News

Paleontologic Agitprop?

Magazine article Insight on the News

Paleontologic Agitprop?

Article excerpt

Life In China must have developed in an entirely different manner than In the West -- at least according to scientists who hold very different views of evolution.

Before smiling officials escorted an international group of foreign scientists to fossil sites in southern China last summer, they made sure gangs of road-building political prisoners were trucked out of sight. The fossil hunters who caught on to this little routine shrugged it off as a problem far from their concerns.

The scientists might have been concerned about their own efforts to hide troublesome matters -- matters that became more apparent when they settled into a resort for a weeklong symposium called "The Origins of Animal Body Plans and the Fossil Record." Though Western journals Nature and Science later carried articles about the 530-million-year-old fossil discoveries announced at this conference, they made no mention of the central questions emphasized by the discoverers themselves: Why do virtually all the 40-some major animal groups, called phyla, appear in the fossil record at the same time? Why don't we see new phyla continuing to evolve after this? And why does the Chinese fossil record show evolution's subsequent history running opposite to traditional evolutionary-tree diagrams?

In the West, the evolution of life is viewed as a cumulative process, the accumulation of change by innumerable, small steps over hundreds of millions of years. Westerners picture an ever-widening tree of life, growing from a single trunk at the bottom and achieving maximum diversity at the top.

In China, however, scientists view evolution more like a onetime event, the greatest changes occurring at the very start of the Cambrian period. Chinese paleontologists interpret their fossil cache as a record of a "macroevolutionary" event that took place 543 million to 535 million years ago. Within that unique window of opportunity, something special happened, something involving a coordinated influx of complex genetic information -- something that demands "harmony," as Chinese paleontologists put it, rather than chance and competition.

Chinese evolutionary theory rarely is discussed in English-language academic journals, even though China is the place Western scientists must go to learn about the origins of animal life on Earth. China contains the only fossils in the world that are dated near the start of the Cambrian period, when complex animal groups first exploded onto the scene. International groups make regular pilgrimages to Yunnan province and other paleontological hot spots.

Westerners have had several decades to get used to the idea of "quicktime" evolution and bushlike, instead of treelike, evolutionary diagrams mostly through the writings of Harvard paleontologist Stephen Jay Gould. Perhaps the best-known paleontologist in the West, he remains the most controversial, and his work receives short shrift in undergraduate textbooks.

Recognizing the lack of fossil evidence for expected transitions between major animal groups, Gould and his colleague Niles Eldredge (of the American Museum of Natural History) promoted a concept they called "punctuated equilibria." According to "punk eek," the fossil record of each animal is characterized by long periods of "equilibrium," where nothing much happens; this tranquil state occasionally is "punctuated" by quick jumps involving massive changes in the animal. Gould stresses the role of "contingency," or chance happenings, in provoking these major changes. Rerun the tape of life, he says, and vertebrates, let alone humans, might never appear.

In his 1989 book, Wonderful Life, Gould praised the Burgess Shale fossils -- another key group of Cambrian fossils discovered in Canada -- for the "exquisite detail" of their preservation, providing scientists with insight into a crucial period. From his study of these fossils, Gould concluded that no gradual steps possibly could connect pre-Cambrian fungus with the Cambrian animals. …

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