The Garden of Ediacara: Discovering the First Complex Life

The Garden of Ediacara: Discovering the First Complex Life

The Garden of Ediacara: Discovering the First Complex Life

The Garden of Ediacara: Discovering the First Complex Life


During an expedition in Sonora, Mexico, paleontologist Mark A. S. McMenamin unearthed fossils of creatures dated at approximately 600 million years old -- making them the oldest large body fossils ever discovered. These circular fossils, known as Ediacarans, seemed to defy explanation. Representatives of marine life forms that existed in Precambrian times, as much as fifty million years before life on earth began to diversify rapidly, the specimens bore a superficial resemblance to jellyfish. A typical Ediacaran had a quilted body, three curving arms at the center, and a fringe of fine radial lines. McMenamin's curiosity was fueled by the puzzle of whether the Ediacarans were animals or some other type of organism. How could such complex forms of life appear so suddenly, without extensive records of prior evolution? Yet, this seems to be exactly what the Ediacarans had done. The Garden of Ediacara presents a mesmerizing documentary of a major scientific discovery, detailing McMenamin's trip to Namibia, where, with a party that included the renowned paleontologist Adolf Seilacher, the author investigates a spectacular cast made from a colony of fossils in the Nama desert. He chronicles the long, often futile search made by earlier scientists for Ediacara, which began more than a century ago in Europe, North America, and Africa, and the various types of Ediacaran fossils that have been uncovered in the years since. McMenamin concludes that Ediacarans were not animals because they never passed through the ball-shaped embryonic stage peculiar to known animal life forms. But, remarkably, Ediacarans seem to have developed a central nervous system and a brain independent from animal evolution. This startling conclusion has profound implications for our understanding of evolutionary biology, for it indicates that the path toward intelligent life was embarked upon more than once on this planet.


Dorion Sagan

Virtually as soon as earth's crust cools enough to be hospitable to life, we find evidence of life on its surface. But we are latecomers, and just as we must be familiar with the beginning of a mystery novel to understand its end, we must scrutinize the often ignored early phase of evolution. Mark McMenamin's allusively named Garden of Ediacara hones in on some of the key events and players in life's early phase—a time for the biosphere that, like the first three years of a human life, is not only formative and revealing but essential to understanding the full sweep of a living existence.

Da Vinci found shells on mountains that suggested a long geological past. Hutton and, later, Darwin extended such thinking, drawing forth a temporal expanse wide enough to explain modern anomalies and complexities. But when early commentators surveyed the fossil history of life on earth, they were not overly impressed with life's earliest phase. It almost seemed as if nothing was going on. Until the “Cambrian explosion”—the widespread appearance of fossil forms, including the famous horseshoe-crab-like trilobites, during the Cambrian geological period—it seemed as if life had barely started. Now you don't see them, now you do: Like the goddess Minerva bursting forth fully formed from the head of Zeus, the sudden appearance of hard-backed animals in the fossil record had about it the lingering aura of myth or celestial-fostered miracle.

Whence come animals from evolutionary chaos?

For geologist Preston Cloud, one of the first of the modern paleobiologists, the appearance of animal life corresponded to a global atmospheric increase in free oxygen. This theory, repeated in textbooks, may be an anthropomorphic fairy tale, a kind of industrial fiction. Fire-starting oxygen, the gas of choice, spurs the biosphere to produce complex life forms, paving the way for air-breathing mammals. But there is probably no . . .

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