A Short History of Nearly Everything

by Bill Bryson

  It may come as a slight comfort to know that bacteria can themselves get sick. They are sometimes infected by bacteriophages (or simply phages), a type of virus. A virus is a strange and unlovely entity--"a piece of nucleic acid surrounded by bad news" in the memorable phrase of the Nobel laureate Peter Medawar. Smaller and simpler than bacteria, viruses aren't themselves alive. In isolation they are inert and harmless. But introduce them into a suitable host and they burst into busyness--into life. About five thousand types of virus are known, and between them they afflict us with many hundreds of diseases, ranging from the flu and common cold to those that are most invidious to human well-being: smallpox, rabies, yellow fever, ebola, polio, and the human immunodeficiency virus, the source of AIDS.

  Viruses prosper by hijacking the genetic material of a living cell and using it to produce more virus. They reproduce in a fanatical manner, then burst out in search of more cells to invade. Not being living organisms themselves, they can afford to be very simple. Many, including HIV, have ten genes or fewer, whereas even the simplest bacteria require several thousand. They are also very tiny, much too small to be seen with a conventional microscope. It wasn't until 1943 and the invention of the electron microscope that science got its first look at them. But they can do immense damage. Smallpox in the twentieth century alone killed an estimated 300 million people.

  They also have an unnerving capacity to burst upon the world in some new and startling form and then to vanish again as quickly as they came. In 1916, in one such case, people in Europe and America began to come down with a strange sleeping sickness, which became known as encephalitis lethargica. Victims would go to sleep and not wake up. They could be roused without great difficulty to take food or go to the lavatory, and would answer questions sensibly--they knew who and where they were--though their manner was always apathetic.

  However, the moment they were permitted to rest, they would sink at once back into deepest slumber and remain in that state for as long as they were left. Some went on in this manner for months before dying. A very few survived and regained consciousness but not their former liveliness. They existed in a state of profound apathy, "like extinct volcanoes," in the words of one doctor. In ten years the disease killed some five million people and then quietly went away. It didn't get much lasting attention because in the meantime an even worse epidemic--indeed, the worst in history--swept across the world.

  It is sometimes called the Great Swine Flu epidemic and sometimes the Great Spanish Flu epidemic, but in either case it was ferocious. World War I killed twenty-one million people in four years; swine flu did the same in its first four months. Almost 80 percent of American casualties in the First World War came not from enemy fire, but from flu. In some units the mortality rate was as high as 80 percent.

  Swine flu arose as a normal, nonlethal flu in the spring of 1918, but somehow over the following months--no one knows how or where--it mutated into something more severe. A fifth of victims suffered only mild symptoms, but the rest became gravely ill and often died. Some succumbed within hours; others held on for a few days.

  In the United States, the first deaths were recorded among sailors in Boston in late August 1918, but the epidemic quickly spread to all parts of the country. Schools closed, public entertainments were shut down, people everywhere wore masks. It did little good. Between the autumn of 1918 and spring of the following year, 548,452 people died of the flu in America. The toll in Britain was 220,000, with similar numbers dead in France and Germany. No one knows the global toll, as records in the Third World were often poor, but it was not less than 20 million and probably more like 50 million. Some estimates have put the global total as high as 100 million.

  In an attempt to devise a vaccine, medical authorities conducted tests on volunteers at a military prison on Deer Island in Boston Harbor. The prisoners were promised pardons if they survived a battery of tests. These tests were rigorous to say the least. First the subjects were injected with infected lung tissue taken from the dead and then sprayed in the eyes, nose, and mouth with infectious aerosols. If they still failed to succumb, they had their throats swabbed with discharges taken from the sick and dying. If all else failed, they were required to sit open-mouthed while a gravely ill victim was helped to cough into their faces.

  Out of--somewhat amazingly--three hundred men who volunteered, the doctors chose sixty-two for the tests. None contracted the flu--not one. The only person who did grow ill was the ward doctor, who swiftly died. The probable explanation for this is that the epidemic had passed through the prison a few weeks earlier and the volunteers, all of whom had survived that visitation, had a natural immunity.

  Much about the 1918 flu is understood poorly or not at all. One mystery is how it erupted suddenly, all over, in places separated by oceans, mountain ranges, and other earthly impediments. A virus can survive for no more than a few hours outside a host body, so how could it appear in Madrid, Bombay, and Philadelphia all in the same week?

  The probable answer is that it was incubated and spread by people who had only slight symptoms or none at all. Even in normal outbreaks, about 10 percent of people have the flu but are unaware of it because they experience no ill effects. And because they remain in circulation they tend to be the great spreaders of the disease.

  That would account for the 1918 outbreak's widespread distribution, but it still doesn't explain how it managed to lay low for several months before erupting so explosively at more or less the same time all over. Even more mysterious is that it was primarily devastating to people in the prime of life. Flu normally is hardest on infants and the elderly, but in the 1918 outbreak deaths were overwhelmingly among people in their twenties and thirties. Older people may have benefited from resistance gained from an earlier exposure to the same strain, but why the very young were similarly spared is unknown. The greatest mystery of all is why the 1918 flu was so ferociously deadly when most flus are not. We still have no idea.

  From time to time certain strains of virus return. A disagreeable Russian virus known as H1N1 caused severe outbreaks over wide areas in 1933, then again in the 1950s, and yet again in the 1970s. Where it went in the meantime each time is uncertain. One suggestion is that viruses hide out unnoticed in populations of wild animals before trying their hand at a new generation of humans. No one can rule out the possibility that the Great Swine Flu epidemic might once again rear its head.

  And if it doesn't, others well might. New and frightening viruses crop up all the time. Ebola, Lassa, and Marburg fevers all have tended to flare up and die down again, but no one can say that they aren't quietly mutating away somewhere, or simply awaiting the right opportunity to burst forth in a catastrophic manner. It is now apparent that AIDS has been among us much longer than anyone originally suspected. Researchers at the Manchester Royal Infirmary in England discovered that a sailor who had died of mysterious, untreatable causes in 1959 in fact had AIDS. But for whatever reasons the disease remained generally quiescent for another twenty years.

  The miracle is that other such diseases haven't gone rampant. Lassa fever, which wasn't first detected until 1969, in West Africa, is extremely virulent and little understood. In 1969, a doctor at a Yale University lab in New Haven, Connecticut, who was studying Lassa fever came down with it. He survived, but, more alarmingly, a technician in a nearby lab, with no direct exposure, also contracted the disease and died.

  Happily the outbreak stopped there, but we can't count on such good fortune always. Our lifestyles invite epidemics. Air travel makes it possible to spread infectious agents across the planet with amazing ease. An ebola virus could begin the day in, say, Benin, and finish it in New York or Hamburg or Nairobi, or all three. It means also that medical authorities increasingly need to be acquainted with pretty much every malady that exists everywhere, but of course they are not. In 1990, a Nigerian living in Chicago was exposed to Lassa fever on a visit to his homeland, but didn't develop symptoms until he had returned to the United States. He d
ied in a Chicago hospital without diagnosis and without anyone taking any special precautions in treating him, unaware that he had one of the most lethal and infectious diseases on the planet. Miraculously, no one else was infected. We may not be so lucky next time.

  And on that sobering note, it's time to return to the world of the visibly living.

  21 LIFE GOES ON

  IT ISN'T EASY to become a fossil. The fate of nearly all living organisms--over 99.9 percent of them--is to compost down to nothingness. When your spark is gone, every molecule you own will be nibbled off you or sluiced away to be put to use in some other system. That's just the way it is. Even if you make it into the small pool of organisms, the less than 0.1 percent, that don't get devoured, the chances of being fossilized are very small.

  In order to become a fossil, several things must happen. First, you must die in the right place. Only about 15 percent of rocks can preserve fossils, so it's no good keeling over on a future site of granite. In practical terms the deceased must become buried in sediment, where it can leave an impression, like a leaf in wet mud, or decompose without exposure to oxygen, permitting the molecules in its bones and hard parts (and very occasionally softer parts) to be replaced by dissolved minerals, creating a petrified copy of the original. Then as the sediments in which the fossil lies are carelessly pressed and folded and pushed about by Earth's processes, the fossil must somehow maintain an identifiable shape. Finally, but above all, after tens of millions or perhaps hundreds of millions of years hidden away, it must be found and recognized as something worth keeping.

  Only about one bone in a billion, it is thought, ever becomes fossilized. If that is so, it means that the complete fossil legacy of all the Americans alive today--that's 270 million people with 206 bones each--will only be about fifty bones, one quarter of a complete skeleton. That's not to say of course that any of these bones will actually be found. Bearing in mind that they can be buried anywhere within an area of slightly over 3.6 million square miles, little of which will ever be turned over, much less examined, it would be something of a miracle if they were. Fossils are in every sense vanishingly rare. Most of what has lived on Earth has left behind no record at all. It has been estimated that less than one species in ten thousand has made it into the fossil record. That in itself is a stunningly infinitesimal proportion. However, if you accept the common estimate that the Earth has produced 30 billion species of creature in its time and Richard Leakey and Roger Lewin's statement (in The Sixth Extinction ) that there are 250,000 species of creature in the fossil record, that reduces the proportion to just one in 120,000. Either way, what we possess is the merest sampling of all the life that Earth has spawned.

  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 consist of just one venturesome species but dozens, and didn't appear in one or two locations but all over. Many thinking people in the nineteenth century saw this as proof of God's handiwork and refutation of Darwin's evolutionary ideals. If evolution proceeded slowly, they asked, then how did he account for this sudden appearance of complex, fully formed creatures? The fact is, he couldn't.

  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 On the Origin of Species , when a paleontologist named Charles Doolittle Walcott made an extraordinary find in the Canadian Rockies.

  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 Wonderful Life .

  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.