A short history of nearly everything - Bill Bryson [160]
Moreover, the record we do have is hopelessly skewed. Most land animals, of course, don't die in sediments. They drop in the open and are eaten or left to rot or weather down to nothing. The fossil record consequently is almost absurdly biased in favor of marine creatures. About 95 percent of all the fossils we possess are of animals that once lived under water, mostly in shallow seas.
I mention all this to explain why on a gray day in February I went to the Natural History Museum in London to meet a cheerful, vaguely rumpled, very likeable paleontologist named Richard Fortey.
Fortey knows an awful lot about an awful lot. He is the author of a wry, splendid book called Life: An Unauthorised Biography, which covers the whole pageant of animate creation. But his first love is a type of marine creature called trilobites that once teemed in Ordovician seas but haven't existed for a long time except in fossilized form. All shared a basic body plan of three parts, or lobes—head, tail, thorax—from which comes the name. Fortey found his first when he was a boy clambering over rocks at St. David's Bay in Wales. He was hooked for life.
He took me to a gallery of tall metal cupboards. Each cupboard was filled with shallow drawers, and each drawer was filled with stony trilobites—twenty thousand specimens in all.
“It seems like a big number,” he agreed, “but you have to remember that millions upon millions of trilobites lived for millions upon millions of years in ancient seas, so twenty thousand isn't a huge number. And most 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 Profallotaspis or Elenellus as big as a crab will pop into your waiting hands.” These were creatures with limbs, gills, nervous systems, probing antennae, “a brain of sorts,” in Fortey's words, and the strangest eyes ever seen. Made of calcite rods, the same stuff that forms limestone, they constituted the earliest visual systems known. More than this, the earliest trilobites didn't