of these are only partial specimens. Finding a complete trilobite fossil is still a big moment for a paleontologist.”
Trilobites first appeared-fully formed, seemingly from nowhere-about 540 million years ago, near the start of the great outburst of complex life popularly known as the Cambrian explosion, and then vanished, along with a great deal else, in the great and still mysterious Permian extinction 300,000 or so centuries later. As with all extinct creatures, there is a natural temptation to regard them as failures, but in fact they were among the most successful animals ever to live. Their reign ran for 300 million years-twice the span of dinosaurs, which were themselves one of history’s great survivors. Humans, Fortey points out, have survived so far for one-half of 1 percent as long.
With so much time at their disposal, the trilobites proliferated prodigiously. Most remained small, about the size of modern beetles, but some grew to be as big as platters. Altogether they formed at least five thousand genera and sixty thousand species-though more turn up all the time. Fortey had recently been at a conference in South America where he was approached by an academic from a small provincial university in Argentina. “She had a box that was full of interesting things-trilobites that had never been seen before in South America, or indeed anywhere, and a great deal else. She had no research facilities to study them and no funds to look for more. Huge parts of the world are still unexplored.”
“In terms of trilobites?”
“No, in terms of everything.”
Throughout the nineteenth century, trilobites were almost the only known forms of early complex life, and for that reason were assiduously collected and studied. The big mystery about them was their sudden appearance. Even now, as Fortey says, it can be startling to go to the right formation of rocks and to work your way upward through the eons finding no visible life at all, and then suddenly “a whole
And so matters seemed destined to remain forever until one day in 1909, three months shy of the fiftieth anniversary of the publication of Darwin’s
Walcott was born in 1850 and grew up near Utica, New York, in a family of modest means, which became more modest still with the sudden death of his father when Walcott was an infant. As a boy Walcott discovered that he had a knack for finding fossils, particularly trilobites, and built up a collection of sufficient distinction that it was bought by Louis Agassiz for his museum at Harvard for a small fortune-about $70,000 in today’s money. Although he had barely a high school education and was self taught in the sciences, Walcott became a leading authority on trilobites and was the first person to establish that trilobites were arthropods, the group that includes modern insects and crustaceans.
In 1879 he took a job as a field researcher with the newly formed United States Geological Survey and served with such distinction that within fifteen years he had risen to be its head. In 1907 he was appointed secretary of the Smithsonian Institution, where he remained until his death in 1927. Despite his administrative obligations, he continued to do fieldwork and to write prolifically. “His books fill a library shelf,” according to Fortey. Not incidentally, he was also a founding director of the National Advisory Committee for Aeronautics, which eventually became the National Aeronautics and Space Agency, or NASA, and thus can rightly be considered the grandfather of the space age.
But what he is remembered for now is an astute but lucky find in British Columbia, high above the little town of Field, in the late summer of 1909. The customary version of the story is that Walcott, accompanied by his wife, was riding on horseback on a mountain trail beneath the spot called the Burgess Ridge when his wife’s horse slipped on loose stones. Dismounting to assist her, Walcott discovered that the horse had turned a slab of shale that contained fossil crustaceans of an especially ancient and unusual type. Snow was falling-winter comes early to the Canadian Rockies-so they didn’t linger, but the next year at the first opportunity Walcott returned to the spot. Tracing the presumed route of the rocks’ slide, he climbed 750 feet to near the mountain’s summit. There, 8,000 feet above sea level, he found a shale outcrop, about the length of a city block, containing an unrivaled array of fossils from soon after the moment when complex life burst forth in dazzling profusion-the famous Cambrian explosion. Walcott had found, in effect, the holy grail of paleontology. The outcrop became known as the Burgess Shale, and for a long time it provided “our sole vista upon the inception of modern life in all its fullness,” as the late Stephen Jay Gould recorded in his popular book
Gould, ever scrupulous, discovered from reading Walcott’s diaries that the story of the Burgess Shale’s discovery appears to have been somewhat embroidered-Walcott makes no mention of a slipping horse or falling snow-but there is no disputing that it was an extraordinary find.
It is almost impossible for us whose time on Earth is limited to a breezy few decades to appreciate how remote in time from us the Cambrian outburst was. If you could fly backwards into the past at the rate of one year per second, it would take you about half an hour to reach the time of Christ, and a little over three weeks to get back to the beginnings of human life. But it would take you twenty years to reach the dawn of the Cambrian period. It was, in other words, an extremely long time ago, and the world was a very different place.
For one thing, 500-million-plus years ago when the Burgess Shale was formed it wasn’t at the top of a mountain but at the foot of one. Specifically it was a shallow ocean basin at the bottom of a steep cliff. The seas of that time teemed with life, but normally the animals left no record because they were soft-bodied and decayed upon dying. But at Burgess the cliff collapsed, and the creatures below, entombed in a mudslide, were pressed like flowers in a book, their features preserved in wondrous detail.
In annual summer trips from 1910 to 1925 (by which time he was seventy-five years old), Walcott excavated tens of thousands of specimens (Gould says 80,000; the normally unimpeachable fact checkers of
Unfortunately, according to Gould, Walcott failed to discern the significance of what he had found. “Snatching defeat from the jaws of victory,” Gould wrote in another work,
Walcott died in 1927 and the Burgess fossils were largely forgotten. For nearly half a century they stayed shut away in drawers in the American Museum of Natural History in Washington, seldom consulted and never questioned. Then in 1973 a graduate student from Cambridge University named Simon Conway Morris paid a visit to the collection. He was astonished by what he found. The fossils were far more varied and magnificent than Walcott had indicated in his writings. In taxonomy the category that describes the basic body plans of all organisms is the phylum, and here, Conway Morris concluded, were drawer after drawer of such anatomical singularities-all amazingly and unaccountably unrecognized by the man who had found them.
With his supervisor, Harry Whittington, and fellow graduate student Derek Briggs, Conway Morris spent the next several years making a systematic revision of the entire collection, and cranking out one exciting monograph after another as discovery piled upon discovery. Many of the creatures employed body plans that were not simply unlike anything seen before or since, but were
