A Short History of Nearly Everything

by Bill Bryson

And there is more still. DNA, proteins and the other components of life couldn’t prosper without some sort of membrane to contain them.

Life's raw material - A membrane to act as container

The idea that earthly life might have arrived from space has a surprisingly long and even occasionally distinguished history. The great Lord Kelvin himself raised the possibility as long ago as 1871 at a meeting of the British Association for the Advancement of Science, when he suggested that ‘the germs of life might have been brought to the earth by some meteorite.’ But it remained little more than a fringe notion until one Sunday in September 1969 when tens of thousands of Australians were startled by a series of sonic booms and the sight of a fireball streaking from east to west across the sky17. The fireball made a strange crackling sound as it passed and left behind a smell that some likened to methylated spirits and others described as just awful. The fireball exploded above Murchison, a town of six hundred people in the Goulburn Valley north of Melbourne, and came raining down in chunks, some weighing over 5 kilograms. Fortunately, no-one was hurt. The meteorite was of a rare type known as a carbonaceous chondrite, and the townspeople helpfully collected and brought in some 90 kilograms of it. The timing could hardly have been better. Less than two months earlier, the Apollo 11 astronauts had returned to Earth with a bag full of lunar rocks, so labs throughout the world were geared up – indeed, clamouring – for rocks of extraterrestrial origin. The Murchison meteorite was found to be 4.5 billion years old, and it was studded with amino acids – seventy-four types in ...

Support for idea of life coming from space

Bill Compston, who is now retired but in the 1970s built the world’s first Sensitive High Resolution Ion Micro Probe – or SHRIMP, as it is more affectionately known from its initial letters. This is a machine that measures the decay rate of uranium in tiny minerals called zircons. Zircons appear in most rocks apart from basalts and are extremely durable, surviving every natural process but subduction. Most of the Earth’s crust has been slipped back into the interior at some point, but just occasionally – in Western Australia and Greenland, for example – geologists have found outcrops of rocks that have remained always at the surface. Compston’s machine allowed such rocks to be dated with unparalleled precision. The prototype SHRIMP was built and machined in the Earth Sciences Department’s own workshops, and looked like something that had been built from spare parts on a budget, but it worked great. On its first formal test, in 1982, it dated the oldest thing ever found – a 4.3-billion-year-old rock from Western Australia.

Bill Compston - SHRIMP machine - uranium decay Rate in zircons

the machine, by bombarding a sample of rock with streams of charged atoms, is able to detect subtle differences in the amounts of lead and uranium in the zircon samples, by which means the age of rocks can be accurately adduced. Bob told me that it takes about seventeen minutes to read one zircon and it is necessary to read dozens from each rock to make the data reliable.

How SHRIMP Machine works (dates zircon)

3.5 billion years ago, just when life was getting going, in the ancient period known to earth science as the Archaean.

Archaean period

Anniversaries were few and far between in the Archaean world. For two billion years bacterial organisms were the only forms of life. They lived, they reproduced, they swarmed, but they didn’t show any particular inclination to move on to another, more challenging level of existence. At some point in the first billion years of life, cyanobacteria, or blue-green algae, learned to tap into a freely available resource – the hydrogen that exists in spectacular abundance in water. They absorbed water molecules, supped on the hydrogen and released the oxygen as waste, and in so doing invented photosynthesis. As Margulis and Sagan note, photosynthesis is ‘undoubtedly the most important single metabolic innovation in the history of life on the planet24’ – and it was invented not by plants but by bacteria.

Photosynthesis - inventged by bacteria (blue gree algae) - increased oxygen level in atmosphere

As cyanobacteria proliferated the world began to fill with O2, to the consternation of those organisms that found it poisonous – which in those days was all of them. In an anaerobic (or non-oxygen-using) world, oxygen is extremely poisonous. Our white blood cells actually use oxygen to kill invading bacteria25. That oxygen is fundamentally toxic often comes as a surprise to those of us who find it so convivial to our well-being, but that is only because we have evolved to exploit it. To other things it is a terror. It is what turns butter rancid and makes iron rust. Even we can tolerate it only up to a point. The oxygen level in our cells is only about a tenth the level found in the atmosphere. The new oxygen-using organisms had two advantages. Oxygen was a more efficient way to produce energy, and it vanquished competitor organisms. Some retreated into the oozy, anaerobic world of bogs and lake bottoms. Others did likewise but then later (much later) migrated to the digestive tracts of beings like you and me. Quite a number of these primeval entities are alive inside your body right now, helping to digest your food, but abhorring even the tiniest hint of O2. Untold number of others failed to adapt and died. The cyanobacteria were a runaway success. At first, the extra oxygen they produced didn’t accumulate in the atmosphere, but combined with iron to form ferric oxides, which sank to the bottom of primitive seas. For millions of years, the world literally rusted – a pheno...

Consequences of increase in Oxygen in atmosphere 3.5 billion years back

about 3.5 billion years ago something more emphatic became apparent26. Wherever the seas were shallow, visible structures began to appear. As they went through their chemical routines, the cyanobacteria became very slightly tacky, and that tackiness trapped micro-particles of dust and sand, which became bound together to form slightly weird but solid structures – the stromatolites that featured in the shallows of the poster on Victoria Bennett’s office wall. Stromatolites came in various shapes and sizes. Sometimes they looked like enormous cauliflowers, sometimes like fluffy mattresses (stromatolite comes from the Greek for mattress); sometimes they came in the form of columns, rising tens of metres above the surface of the water – on occasion as high as 100 metres. In all their manifestations, they were a kind of living rock, and they represented the world’s first co-operative venture, with some varieties of primitive organism living just at the surface and others living just underneath, each taking advantage of conditions created by the other. The world had its first ecosystem.

Conersion of algae to StromatolItes - a bacterial rock

in 1961 they got a real surprise with the discovery of a community of living stromatolites at Shark Bay on the remote northwest coast of Australia. This was most unexpected – so unexpected, in fact, that it was some years before scientists realized quite what they had found. Today, however, Shark Bay is a tourist attraction – or at least as much of a tourist attraction as a place hundreds of miles from anywhere much and dozens of miles from anywhere at all can ever be. Boardwalks have been built out into the bay so that visitors can stroll over the water to get a good look at the stromatolites, quietly respiring just beneath the surface. They are lustreless and grey and look, as I recorded in an earlier book, like very large cow-pats. But it is a curiously giddying moment to find yourself staring at living remnants of the Earth as it was 3.5 billion years ago. As Richard Fortey has put it: ‘This is truly time travelling27, and if the world were attuned to its real wonders this sight would be as well-known as the pyramids of Giza.’ Although you’d never guess it, these dull rocks swarm with life, with an estimated (well, obviously estimated) three billion individual organisms on every square yard of rock. Sometimes when you look carefully you can see tiny strings of bubbles rising to the surface as they give up their oxygen. In two billion years such tiny exertions raised the level of oxygen in the Earth’s atmosphere to 20 per cent, preparing the way for the next, more compl...

Still living stromatolites on earth - Australia

once the stage was set, and apparently quite suddenly, an entirely new type of cell arose – one containing a nucleus and other little bodies collectively called organelles (from a Greek word meaning ‘little tools’). The process is thought to have started when some blundering or adventuresome bacterium either invaded or was captured by some other bacterium and it turned out that this suited them both. The captive bacterium became, it is thought, a mitochondrion. This mitochondrial invasion (or endosymbiotic event, as biologists like to term it) made complex life possible. (In plants a similar invasion produced chloroplasts, which enable plants to photosynthesize.)

Creation of mitochondria and chloroplasts after increase in oxygen level on earth

Mitochondria manipulate oxygen in a way that liberates energy from foodstuffs. Without this niftily facilitating trick, life on Earth today would be nothing more than a sludge of simple microbes30. Mitochondria are very tiny – you could pack a billion into the space occupied by a grain of sand31 – but also very hungry. Almost every nutriment you absorb goes to feeding them.

Mitochondria Function in cell - Energy liberation from food

We couldn’t live for two minutes without them, yet even after a billion years mitochondria behave as if they think things might not work out between us. They maintain their own DNA, RNA and ribosomes. They reproduce at a different time from their host cells. They look like bacteria, divide like bacteria and sometimes respond to antibiotics in the way bacteria do. They don’t even speak the same genetic language as the cell in which they live. In short, they keep their bags packed. It is like having a stranger in your house, but one who has been there for a billion years.

Mitochondria - different behaviour from host cell

The new type of cells are known as eukaryotes (meaning ‘truly nucleated’), as contrasted with the old type, which are known as prokaryotes (‘pre-nucleated’), and they seem to have arrived suddenly in the fossil record. The oldest eukaryotes yet known, called Grypania, were discovered in iron sediments in Michigan in 1992. Such fossils have been found just once and then no more are known for 500 million years32

Prokaryotes and Eukaryotes - Old and new cell types created on earth

The simple amoeba, just one cell big and without any ambitions but to exist, contains 400 million bits of genetic information in its DNA – enough, as Carl Sagan noted, to fill 80 books of 500 pages34.

Example of enormous genetic information in DNA

If you are in good health and averagely diligent about hygiene, you will have a herd of about one trillion bacteria grazing on your fleshy plains2 – about a hundred thousand of them on every square centimetre of skin. They are there to dine off the ten billion or so flakes of skin you shed every day, plus all the tasty oils and fortifying minerals that seep out from every pore and fissure. You are for them the ultimate buffet, with the convenience of warmth and constant mobility thrown in. By way of thanks, they give you B.O. And those are just the bacteria that inhabit your skin. There are trillions more tucked away in your gut and nasal passages, clinging to your hair and eyelashes, swimming over the surface of your eyes, drilling through the enamel of your teeth. Your digestive system alone is host to more than a hundred trillion microbes, of at least four hundred types3. Some deal with sugars, some with starches, some attack other bacteria. A surprising number, like the ubiquitous intestinal spirochetes, have no detectable function at all4. They just seem to like to be with you. Every human body consists of about ten quadrillion cells, but is host to about a hundred quadrillion bacterial cells5. They are, in short, a big part of us. From the bacteria’s point of view, of course, we are a rather small part of them.

Bacteria around us

Bacteria, never forget, got along for billions of years without us. We couldn’t survive a day without them6. They process our wastes and make them usable again; without their diligent munching nothing would rot. They purify our water and keep our soils productive. Bacteria synthesize vitamins in our gut, convert the things we eat into useful sugars and polysaccharides, and go to war on alien microbes that slip down our gullet. We depend totally on bacteria to pluck nitrogen from the air and convert it into useful nucleotides and amino acids for us. It is a prodigious and gratifying feat. As Margulis and Sagan note, to do the same thing industrially (as when making fertilizers) manufacturers must heat the source materials to 500 degrees Celsius and squeeze them to 300 times normal pressures. Bacteria do the same thing all the time without fuss, and thank goodness, for no larger organism could survive without the nitrogen they pass on. Above all, microbes continue to provide us with the air we breathe and to keep the atmosphere stable. Microbes, including the modern versions of cyanobacteria, supply the greater part of the planet’s breathable oxygen. Algae and other tiny organisms bubbling away in the sea blow out about 150 billion kilograms of the stuff every year7.

Inportance of bacteria

About once every million divisions, they produce a mutant. Usually this is bad luck for the mutant – for an organism, change is always risky – but just occasionally the new bacterium is endowed with some accidental advantage, such as the ability to elude or shrug off an attack of antibiotics. With this ability to evolve rapidly goes another, even scarier advantage. Bacteria share information. Any bacterium can take pieces of genetic coding from any other. Essentially, as Margulis and Sagan put it, all bacteria swim in a single gene pool11. Any adaptive change that occurs in one area of the bacterial universe can spread to any other. It’s rather as if a human could go to an insect to get the necessary genetic coding to sprout wings or walk on ceilings. It means that from a genetic point of view bacteria have become a single super-organism – tiny, dispersed, but invincible. They will live and thrive on almost anything you spill, dribble or shake loose. Just give them a little moisture – as when you run a damp cloth over a counter – and they will bloom as if created from nothing. They will eat wood, the glue in wallpaper, the metals in hardened paint. Scientists in Australia found microbes known as Thiobacillus concretivorans12 which lived in – indeed, could not live without – concentrations of sulphuric acid strong enough to dissolve metal. A species called Micrococcus radiophilus was found living happily in the waste tanks of nuclear reactors, gorging itself on plutonium an...

Mutation In Bacteria

About once every million divisions, they produce a mutant. Usually this is bad luck for the mutant – for an organism, change is always risky – but just occasionally the new bacterium is endowed with some accidental advantage, such as the ability to elude or shrug off an attack of antibiotics. With this ability to evolve rapidly goes another, even scarier advantage. Bacteria share information. Any bacterium can take pieces of genetic coding from any other. Essentially, as Margulis and Sagan put it, all bacteria swim in a single gene pool11. Any adaptive change that occurs in one area of the bacterial universe can spread to any other. It’s rather as if a human could go to an insect to get the necessary genetic coding to sprout wings or walk on ceilings. It means that from a genetic point of view bacteria have become a single super-organism – tiny, dispersed, but invincible. They will live and thrive on almost anything you spill, dribble or shake loose. Just give them a little moisture – as when you run a damp cloth over a counter – and they will bloom as if created from nothing. They will eat wood, the glue in wallpaper, the metals in hardened paint. Scientists in Australia found microbes known as Thiobacillus concretivorans12 which lived in – indeed, could not live without – concentrations of sulphuric acid strong enough to dissolve metal. A species called Micrococcus radiophilus was found living happily in the waste tanks of nuclear reactors, gorging itself on plutonium an...

Invincible And indestructible bacteria

At depth, microbes shrink in size and become extremely sluggish. The liveliest of them may divide no more than once a century18, some no more than perhaps once in five hundred years. As The Economist has put it: ‘The key to long life, it seems, is not to do too much19.’ When things are really tough, bacteria are prepared to shut down all systems and wait for better times. In 1997 scientists successfully activated some anthrax spores that had lain dormant for eighty years in a museum display in Trondheim, Norway. Other micro-organisms have leaped back to life after being released from a 118-year-old can of meat and a 166-year-old bottle of beer20. In 1996, scientists at the Russian Academy of Science claimed to have revived bacteria frozen in Siberian permafrost for three million years21. But the record claim for durability so far is one made by Russell Vreeland and colleagues at West Chester University22 in Pennsylvania in 2000, when they announced that they had resuscitated 250-million-year-old bacteria called Bacillus permians that had been trapped in salt deposits 600 metres underground in Carlsbad, New Mexico. If so, this microbe is older than the continents. The report met with some understandable dubiousness. Many biochemists maintained that over such a span the microbe’s components would have become uselessly degraded unless the bacterium roused itself from time to time. However, if the bacterium did stir occasionally, there was no plausible internal source of energ...

Revival of bacteria after certuries

At depth, microbes shrink in size and become extremely sluggish. The liveliest of them may divide no more than once a century18, some no more than perhaps once in five hundred years. As The Economist has put it: ‘The key to long life, it seems, is not to do too much19.’ When things are really tough, bacteria are prepared to shut down all systems and wait for better times. In 1997 scientists successfully activated some anthrax spores that had lain dormant for eighty years in a museum display in Trondheim, Norway. Other micro-organisms have leaped back to life after being released from a 118-year-old can of meat and a 166-year-old bottle of beer20. In 1996, scientists at the Russian Academy of Science claimed to have revived bacteria frozen in Siberian permafrost for three million years21. But the record claim for durability so far is one made by Russell Vreeland and colleagues at West Chester University22 in Pennsylvania in 2000, when they announced that they had resuscitated 250-million-year-old bacteria called Bacillus permians that had been trapped in salt deposits 600 metres underground in Carlsbad, New Mexico. If so, this microbe is older than the continents. The report met with some understandable dubiousness. Many biochemists maintained that over such a span the microbe’s components would have become uselessly degraded unless the bacterium roused itself from time to time. However, if the bacterium did stir occasionally, there was no plausible internal source of energ...

Bacteria Bacillus Permians - story of reviving bacteria in laboratory after 250 million years

the late nineteenth century the German naturalist Ernst Haeckel had suggested that bacteria deserved to be placed in a separate kingdom, which he called Monera,

Monera - bacteria kingdom

unlike all plants, fungi don’t photosynthesize, so they have no chlorophyll and thus are not green. Instead they grow directly on their food source, which can be almost anything. Fungi will eat the sulphur off a concrete wall or the decaying matter between your toes – two things no plant will do. Almost the only plant-like quality they have is that they root.

How fungi is different from plants

Even less comfortably susceptible to categorization was the peculiar group of organisms formally called myxomycetes but more commonly known as slime moulds. The name no doubt has much to do with their obscurity. An appellation that sounded a little more dynamic – ‘ambulant self-activating protoplasm’, say – and less like the stuff you find when you reach deep into a clogged drain would almost certainly have earned these extraordinary entities a more immediate share of the attention they deserve, for slime moulds are, make no mistake, among the most interesting organisms in nature. When times are good, they exist as one-celled individuals, much like amoebas. But when conditions grow tough, they crawl to a central gathering place and become, almost miraculously, a slug. The slug is not a thing of beauty and it doesn’t go terribly far – usually just from the bottom of a pile of leaf litter to the top, where it is in a slightly more exposed position – but for millions of years this may well have been the niftiest trick in the universe. And it doesn’t stop there. Having hauled itself up to a more favourable locale, the slime mould transforms itself yet again, taking on the form of a plant. By some curious orderly process the cells reconfigure, like the members of a tiny marching band, to make a stalk atop of which forms a bulb known as a fruiting body. Inside the fruiting body are millions of spores which, at the appropriate moment, are released to the wind to blow away to beco...

Mysterious slime mould

In 1969, in an attempt to bring some order to the growing inadequacies of classification25, an ecologist from Cornell named R. H. Whittaker unveiled in the journal Science a proposal to divide life into five principal branches – kingdoms, as they are known – called Animalia, Plantae, Fungi, Protista and Monera. Protista was a modification of an earlier term, Protoctista, which had been suggested a century earlier by a Scottish biologist named John Hogg, and was meant to describe any organisms that were neither plant nor animal.

RH Whittaker - System of claassification of life in 5 divisions

Genes, however, allowed Woese to approach micro-organisms from another angle. As he worked, Woese realized that there were more fundamental divisions in the microbial world than anyone suspected. A lot of little organisms that looked like bacteria and behaved like bacteria were actually something else altogether – something that had branched off from bacteria a long time ago. Woese called these organisms archaebacteria, later shortened to archaea.

Carl Woese - Discovery of Archaebacteria

In 1976 he startled the world – or at least the little bit of it that was paying attention – by redrawing the Tree of Life to incorporate not five main divisions, but twenty-three. These he grouped under three new principal categories – Bacteria, Archaea and Eukarya (sometimes spelled Eucarya) – which he called domains. The new arrangement was as follows: Bacteria: cyanobacteria, purple bacteria, gram-positive bacteria, green non-sulphur bacteria, flavobacteria and thermotogales Archaea: halophilic archaeans, methanosarcina, methanobacterium, methanoncoccus, thermoceler, thermoproteus and pyrodictium Eukarya: diplomads, microsporidia, trichomonads, flagellates, entameba, slime moulds, ciliates, plants, fungi and animals

Carl Woese classification of life - from 5 to 23

Making a host unwell has certain benefits for the microbe. The symptoms of an illness often help to spread the disease. Vomiting, sneezing and diarrhoea are excellent methods of getting out of one host and into position for boarding another.

Why microbes make us ill

The most effective strategy of all is to enlist the help of a mobile third party. Infectious organisms love mosquitoes because the mosquito’s sting delivers them directly into a bloodstream where they can get straight to work before the victim’s defence mechanisms can figure out what’s hit them. This is why so many grade A diseases – malaria, yellow fever, dengue fever, encephalitis and a hundred or so other less celebrated but often rapacious maladies – begin with a mosquito bite. It is a fortunate fluke for us that HIV, the AIDS agent, isn’t among them – at least not yet. Any HIV the mosquito sucks up on its travels is dissolved by the mosquito’s own metabolism. When the day comes that the virus mutates its way around this, we may be in real trouble.

Why microbes spread mostly by mosquitoes

Because there are so many things out there with the potential to hurt you, your body holds lots of different varieties of defensive white blood cells – some ten million types in all, each designed to identify and destroy a particular sort of invader. It would be impossibly inefficient to maintain ten million separate standing armies, so each variety of white blood cell keeps only a few scouts on active duty. When an infectious agent – what’s known as an antigen – invades, relevant scouts identify the attacker and put out a call for reinforcements of the right type. While your body is manufacturing these forces, you are likely to feel wretched. The onset of recovery begins when the troops finally swing into action. White cells are merciless and will hunt down and kill every last pathogen they can find. To avoid extinction, attackers have evolved two elemental strategies. Either they strike quickly and move on to a new host, as with common infectious illnesses like flu, or they disguise themselves so that the white cells fail to spot them, as with HIV, the virus responsible for AIDS, which can sit harmlessly and unnoticed in the nuclei of cells for years before springing into action.

How immunity (white blood cell) works

Because there are so many things out there with the potential to hurt you, your body holds lots of different varieties of defensive white blood cells – some ten million types in all, each designed to identify and destroy a particular sort of invader. It would be impossibly inefficient to maintain ten million separate standing armies, so each variety of white blood cell keeps only a few scouts on active duty. When an infectious agent – what’s known as an antigen – invades, relevant scouts identify the attacker and put out a call for reinforcements of the right type. While your body is manufacturing these forces, you are likely to feel wretched. The onset of recovery begins when the troops finally swing into action. White cells are merciless and will hunt down and kill every last pathogen they can find. To avoid extinction, attackers have evolved two elemental strategies. Either they strike quickly and move on to a new host, as with common infectious illnesses like flu, or they disguise themselves so that the white cells fail to spot them, as with HIV, the virus responsible for AIDS, which can sit harmlessly and unnoticed in the nuclei of cells for years before springing into action.

How bacteria saves them from immunity

The scariest, most out-of-control bacterial disorder of the moment is a disease called necrotizing fasciitis in which bacteria essentially eat the victim from the inside out39, devouring internal tissue and leaving behind a pulpy, noxious residue. Patients often come in with comparatively mild complaints – a skin rash and fever, typically – but then dramatically deteriorate. When they are opened up it is often found that they are simply being consumed. The only treatment is what is known as ‘radical excisional surgery’ – cutting out every bit of infected area. Seventy per cent of victims die; many of the rest are left terribly disfigured. The source of the infection is a mundane family of bacteria called Group A Streptococcus, which normally do no more than cause strep throat. Very occasionally, for reasons unknown, some of these bacteria get through the lining of the throat and into the body proper, where they wreak the most devastating havoc. They are completely resistant to antibiotics. About a thousand cases a year occur in the United States and no-one can say that it won’t get worse.

Necrotizing fasciitis - disease where bacteria eats person inside out

Precisely the same thing happens with meningitis. At least 10 per cent of young adults, and perhaps 30 per cent of teenagers, carry the deadly meningococcal bacterium, but it lives quite harmlessly in the throat. Just occasionally – in about one young person in a hundred thousand – it gets into the bloodstream and makes them very ill indeed. In the worst cases, death can come in twelve hours. That’s shockingly quick. ‘You can have a person who’s in perfect health at breakfast and dead by evening,’ says Marsh.

Meningitis - bacterial disease that kills in 12 hour

In 1952, penicillin was fully effective against all strains of staphylococcus bacteria, to such an extent that by the early 1960s the US surgeon-general, William Stewart, felt confident enough to declare: ‘The time has come to close the book on infectious diseases40. We have basically wiped out infection in the United States.’ Even as he spoke, however, some 90 per cent of those strains were in the process of developing immunity to penicillin41. Soon one of these new strains, called methicillin-resistant staphylococcus aureus, began to show up in hospitals. Only one type of antibiotic, vanomycin, remained effective against it, but in 1997 a hospital in Tokyo reported the appearance of a strain that could resist even that42. Within months it had spread to six other Japanese hospitals. All over, the microbes are beginning to win the war again: in US hospitals alone, some fourteen thousand people a year die from infections they pick up there. As James Surowiecki noted43 in a New Yorker article, given a choice between developing antibiotics that people will take every day for two weeks and antidepressants that people will take every day for ever, drug companies not surprisingly opt for the latter. Although a few antibiotics have been toughened up a bit, the pharmaceutical industry hasn’t given us an entirely new antibiotic since the 1970s.

How bacteria evolved against penicillin and other antibiotics

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.

Virus that makes bacteria ill

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.

Virus

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 at once sink 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

Mysterious Viral Sleeping Sickness in 1916

Swine flu arose as a normal, non-lethal 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 many 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 autumn 1918 and spring the following year, 548,452 people died of the flu in America. The toll in Britain was 220,000, with similar numbers 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 twenty million and probably more like fifty million. Some estimates have put the global total as high as a hundred million. In an attempt to devise a vaccine, medical authorities conducted experiments on volunteers at a military prison on Deer Island in Boston Harbor52. 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 straig...

Story of horrifying swine flu epidemic of 1918

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.

A recurring H1N1 virus epidemic

Fortey knows an awful lot about an awful

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 three million 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. They reigned for 300 million years – twice the span of dinosaurs, which were themselves among history’s great survivors. Humans, Fortey points out, have survived so far for one-half of 1 per cent as long

Trilobites - Animal that survived longest - 300 mn years

lichens grew on bare rock without evident nourishment or the production of seeds, many people – educated people – believed they were stones caught in the process of becoming plants. ‘Spontaneously, inorganic stone becomes living plant2!’ rejoiced one observer, a Dr Hornschuch, in 1819. Closer inspection showed that lichens were more interesting than magical. They are in fact a partnership between fungi and algae. The fungi excrete acids which dissolve the surface of the rock, freeing minerals that the algae convert into food sufficient to sustain both. It is not a very exciting arrangement, but it is a conspicuously successful one. The world has more than twenty thousand species of lichens3.

Lichens - how they feed them on bare rocks

If you imagine the 4,500 million years of Earth’s history compressed into a normal earthly day5, then life begins very early, about 4 a.m., with the rise of the first simple, single-celled organisms, but then advances no further for the next sixteen hours. Not until almost eight-thirty in the evening, with the day five-sixths over, has the Earth anything to show the universe but a restless skin of microbes. Then, finally, the first sea plants appear, followed twenty minutes later by the first jellyfish and the enigmatic Ediacaran fauna first seen by Reginald Sprigg in Australia. At 9.04 p.m. trilobites swim onto the scene, followed more or less immediately by the shapely creatures of the Burgess Shale. Just before 10 p.m. plants begin to pop up on the land. Soon after, with less than two hours left in the day, the first land creatures follow. Thanks to ten minutes or so of balmy weather, by 10.24 the Earth is covered in the great carboniferous forests whose residues give us all our coal, and the first winged insects are evident. Dinosaurs plod onto the scene just before 11 p.m. and hold sway for about three-quarters of an hour. At twenty-one minutes to midnight they vanish and the age of mammals begins. Humans emerge one minute and seventeen seconds before midnight. The whole of our recorded history, on this scale, would be no more than a few seconds, a single human lifetime barely an instant. Throughout this greatly speeded-up day, continents slide about and bang together...

History of earth compressed in a day

And how, you may reasonably wonder, can scientists know what oxygen levels were like hundreds of millions of years ago? The answer lies in a slightly obscure but ingenious field known as isotope geochemistry. The long-ago seas of the Carboniferous and Devonian swarmed with tiny plankton which wrapped themselves inside tiny protective shells. Then, as now, the plankton created their shells by drawing oxygen from the atmosphere and combining it with other elements (carbon especially) to form durable compounds such as calcium carbonate. It’s the same chemical trick that goes on in (and is discussed elsewhere in relation to) the long-term carbon cycle – a process that doesn’t make for terribly exciting narrative but is vital for creating a habitable planet. Eventually in this process all the tiny organisms die and drift to the bottom of the sea, where they are slowly compressed into limestone. Among the tiny atomic structures the plankton take to the grave with them are two very stable isotopes – oxygen-16 and oxygen-18. (If you have forgotten what an isotope is, it doesn’t matter, though for the record it’s an atom with an abnormal number of neutrons.) This is where the geochemists come in, for the isotopes accumulate at different rates depending on how much oxygen or carbon dioxide is in the atmosphere8 at the time of their creation. By comparing the ancient rates of deposition of the two isotopes, geochemists can read conditions in the ancient world – oxygen levels, air and...

Isotope geochemistry - Simulating atmosphere millions of years ago

The principal reason oxygen levels were able to build so robustly throughout the period of early terrestrial life was that much of the world’s landscape was dominated by giant tree ferns and vast swamps, which by their boggy nature disrupted the normal carbon recycling process. Instead of completely rotting down, falling fronds and other dead vegetative matter accumulated in rich, wet sediments, which were eventually squeezed into the vast coal beds that sustain much economic activity even now.

Reason For high atmospheric oxygen level (35%) millions of years ago

The heady levels of oxygen clearly encouraged outsized growth. The oldest indication of a surface animal yet found is a track left 350 million years ago by a millipede-like creature on a rock in Scotland. It was over a metre long. Before the era was out some millipedes would reach lengths more than double that.

Oldest land animal fossil

Since life on land began, it has consisted of four megadynasties, as they are sometimes called. The first consisted of primitive, plodding but sometimes fairly hefty amphibians and reptiles. The best-known animal of this age was the Dimetrodon, a sail-backed creature that is commonly confused with dinosaurs (including, I note, in a picture caption in the Carl Sagan book Comet). The Dimetrodon was in fact a synapsid. So, once upon a time, were we. Synapsids were one of the four main divisions of early reptilian life, the others being anapsids, euryapsids and diapsids. The names simply refer to the number and location of small holes found in the sides of their owners’ skulls12. Synapsids had one hole in their lower temples; diapsids had two; euryapsids had a single hole higher up. Over time, each of these principal groupings split into further subdivisions, of which some prospered and some faltered. Anapsids gave rise to the turtles, which for a time, perhaps a touch improbably, appeared poised to predominate as the planet’s most advanced and deadly species, before an evolutionary lurch let them settle for durability rather than dominance. The synapsids divided into four streams, only one of which survived beyond the Permian. Happily, that was the stream we belonged to, and it evolved into a family of protomammals known as therapsids. These formed Megadynasty 2. Unfortunately for the therapsids, their cousins the diapsids were also productively evolving, in their case into d...

Evolution of mammals and dinosaur

The Earth has seen five major extinction episodes in its time – the Ordovician, Devonian, Permian, Triassic and Cretaceous, in that order – and many smaller ones. The Ordovician (440 million years ago) and Devonian (365 million) each wiped out about 80 to 85 per cent of species. The Triassic (210 million years ago) and Cretaceous (65 million years) each wiped out 70–75 per cent of species. But the real whopper was the Permian extinction of about 245 million years ago, which raised the curtain on the long age of the dinosaurs.

5 major extinctions of species on earth

In the Permian, at least 95 per cent of animals known from the fossil record checked out, never to return18. Even about a third of insect species went – the only occasion on which they were lost en masse19. It is as close as we have ever come to total obliteration. ‘It was, truly, a mass extinction20, a carnage of a magnitude that had never troubled the Earth before,’ says Richard Fortey. The Permian event was particularly devastating to sea creatures. Trilobites vanished altogether. Clams and sea urchins nearly went. Virtually all other marine organisms were staggered. Altogether, on land and in the water, it is thought that the Earth lost 52 per cent of its families – that’s the level above genus and below order on the grand scale of life (the subject of the next chapter) – and perhaps as many as 96 per cent of all its species. It would be a long time – as much as 80 million years by one reckoning – before species totals recovered.

Permian extinction - biggest of the 5 major extinctions

In between the big kill-offs, there have also been many smaller, less well-known extinction episodes – the Hemphillian, Frasnian, Famennian, Rancholabrean and a dozen or so others – which were not so devastating to total species numbers, but often critically hit certain populations. Grazing animals, including horses, were nearly wiped out in the Hemphillian event23 about five million years ago. Horses declined to a single species, which appears so sporadically in the fossil record as to suggest that for a time it teetered on the brink of oblivion. Imagine a human history without horses, without grazing animals.

Minor extintions - example of extinction of grazing animals

At least two dozen potential culprits have been identified as causes or prime contributors24, including global warming, global cooling, changing sea levels, oxygen depletion of the seas (a condition known as anoxia), epidemics, giant leaks of methane gas from the sea floor, meteor and comet impacts, runaway hurricanes of a type known as hypercanes, huge volcanic upwellings and catastrophic solar flares.

Probable culprits for historical species extinction