Bill Bryson - A short history of nearly everything

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, Eight Little Piggies , “Walcott then proceeded to misinterpret these magnificent fossils in the deepest possible way.” He placed them into modern groups, making them ancestral to today’s worms, jellyfish, and other creatures, and thus failed to appreciate their distinctness. “Under such an interpretation,” Gould sighed, “life began in primordial simplicity and moved inexorably, predictably onward to more and better.”

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 bizarrely different. One, Opabinia , had five eyes and a nozzle-like snout with claws on the end. Another, a disc-shaped being called Peytoia , looked almost comically like a pineapple slice. A third had evidently tottered about on rows of stilt-like legs, and was so odd that they named it Hallucigenia . There was so much unrecognized novelty in the collection that at one point upon opening a new drawer Conway Morris famously was heard to mutter, “Oh fuck, not another phylum.”

The English team’s revisions showed that the Cambrian had been a time of unparalleled innovation and experimentation in body designs. For almost four billion years life had dawdled along without any detectable ambitions in the direction of complexity, and then suddenly, in the space of just five or ten million years, it had created all the basic body designs still in use today. Name a creature, from a nematode worm to Cameron Diaz, and they all use architecture first created in the Cambrian party.

What was most surprising, however, was that there were so many body designs that had failed to make the cut, so to speak, and left no descendants. Altogether, according to Gould, at least fifteen and perhaps as many as twenty of the Burgess animals belonged to no recognized phylum. (The number soon grew in some popular accounts to as many as one hundred-far more than the Cambridge scientists ever actually claimed.) “The history of life,” wrote Gould, “is a story of massive removal followed by differentiation within a few surviving stocks, not the conventional tale of steadily increasing excellence, complexity, and diversity.” Evolutionary success, it appeared, was a lottery.

One creature that did manage to slip through, a small wormlike being called Pikaia gracilens , was found to have a primitive spinal column, making it the earliest known ancestor of all later vertebrates, including us. Pikaia were by no means abundant among the Burgess fossils, so goodness knows how close they may have come to extinction. Gould, in a famous quotation, leaves no doubt that he sees our lineal success as a fortunate fluke: “Wind back the tape of life to the early days of the Burgess Shale; let it play again from an identical starting point, and the chance becomes vanishingly small that anything like human intelligence would grace the replay.”

Gould’s book was published in 1989 to general critical acclaim and was a great commercial success. What wasn’t generally known was that many scientists didn’t agree with Gould’s conclusions at all, and that it was all soon to get very ugly. In the context of the Cambrian, “explosion” would soon have more to do with modern tempers than ancient physiological facts.

In fact, we now know, complex organisms existed at least a hundred million years before the Cambrian. We should have known a whole lot sooner. Nearly forty years after Walcott made his discovery in Canada, on the other side of the planet in Australia, a young geologist named Reginald Sprigg found something even older and in its way just as remarkable.

In 1946 Sprigg was a young assistant government geologist for the state of South Australia when he was sent to make a survey of abandoned mines in the Ediacaran Hills of the Flinders Range, an expanse of baking outback some three hundred miles north of Adelaide. The idea was to see if there were any old mines that might be profitably reworked using newer technologies, so he wasn’t studying surface rocks at all, still less fossils. But one day while eating his lunch, Sprigg idly overturned a hunk of sandstone and was surprised-to put it mildly-to see that the rock’s surface was covered in delicate fossils, rather like the impressions leaves make in mud. These rocks predated the Cambrian explosion. He was looking at the dawn of visible life.

Sprigg submitted a paper to Nature , but it was turned down. He read it instead at the next annual meeting of the Australian and New Zealand Association for the Advancement of Science, but it failed to find favor with the association’s head, who said the Ediacaran imprints were merely “fortuitous inorganic markings”-patterns made by wind or rain or tides, but not living beings. His hopes not yet entirely crushed, Sprigg traveled to London and presented his findings to the 1948 International Geological Congress, but failed to excite either interest or belief. Finally, for want of a better outlet, he published his findings in the Transactions of the Royal Society of South Australia . Then he quit his government job and took up oil exploration.

Nine years later, in 1957, a schoolboy named John Mason, while walking through Charnwood Forest in the English Midlands, found a rock with a strange fossil in it, similar to a modern sea pen and exactly like some of the specimens Sprigg had found and been trying to tell everyone about ever since. The schoolboy turned it in to a paleontologist at the University of Leicester, who identified it at once as Precambrian. Young Mason got his picture in the papers and was treated as a precocious hero; he still is in many books. The specimen was named in his honor Chamia masoni .

Today some of Sprigg’s original Ediacaran specimens, along with many of the other fifteen hundred specimens that have been found throughout the Flinders Range since that time, can be seen in a glass case in an upstairs room of the stout and lovely South Australian Museum in Adelaide, but they don’t attract a great deal of attention. The delicately etched patterns are rather faint and not terribly arresting to the untrained eye. They are mostly small and disc-shaped, with occasional, vague trailing ribbons. Fortey has described them as “soft-bodied oddities.”

There is still very little agreement about what these things were or how they lived. They had, as far as can be told, no mouth or anus with which to take in and discharge digestive materials, and no internal organs with which to process them along the way. “In life,” Fortey says, “most of them probably simply lay upon the surface of the sandy sediment, like soft, structureless and inanimate flatfish.” At their liveliest, they were no more complex than jellyfish. All the Ediacaran creatures were diploblastic, meaning they were built from two layers of tissue. With the exception of jellyfish, all animals today are triploblastic.