A Short History of Nearly Everything - Kindle Highlights

As a student, frustrated by the limitations of conventional mathematics, he invented an entirely new form, the calculus, but then told no-one about it for twenty-seven years. LOCATION: 800

In 1936, the economist John Maynard Keynes bought a trunk of Newton’s papers at auction and discovered with astonishment that they were overwhelmingly preoccupied not with optics or planetary motions, but with a single-minded quest to turn base metals into precious ones.

Once in a great while, a few times in history, a human mind produces an observation so acute and unexpected that people can’t quite decide which is the more amazing – the fact or the thinking of it.

The precise distance, we now know, is 149.597870691 million kilometres.)

John Michell, among a great deal else, he perceived the wavelike nature of earthquakes, conducted much original research into magnetism and gravity, and, quite extraordinarily, envisioned the possibility of black holes two hundred years before anyone else – a leap that not even Newton could make.

Each time you pick up a book from a table or a coin from the floor you effortlessly overcome the gravitational exertion of an entire planet.

Cavendish announced that the Earth weighed a little over 13,000,000,000,000,000,000,000 pounds, or six billion trillion metric tons23, to use the modern measure. (A metric ton, or tonne, is 1,000 kilograms or 2,205 pounds.)

Today, scientists have at their disposal machines so precise they can detect the weight of a single bacterium and so sensitive that readings can be disturbed by someone yawning seventy-five feet away,

Human beings would split the atom and invent television, nylon and instant coffee before they could figure out the age of their own planet.

Nowadays, and speaking very generally, geological time is divided first into four great chunks known as eras: Precambrian, Palaeozoic (from the Greek meaning ‘old life’), Mesozoic (‘middle life’) and Cenozoic (‘recent life’). These four eras are further divided into anywhere from a dozen to twenty subgroups, usually called periods though sometimes known as systems. Most of these are also reasonably well known: Cretaceous, Jurassic, Triassic, Silurian and so on.fn1

Karl (or Carl) Scheele

Scheele was both an extraordinary and an extraordinarily luckless fellow. A humble pharmacist with little in the way of advanced apparatus, he discovered eight elements – chlorine, fluorine, manganese, barium, molybdenum, tungsten, nitrogen and oxygen – and got credit for none of them

He also discovered many useful compounds, among them ammonia, glycerin and tannic acid, and was the first to see the commercial potential of chlorine as a bleach – all breakthroughs that made other people extremely wealthy.

Even more remarkable was Scheele’s failure to receive credit for the discovery of chlorine. Nearly all textbooks still attribute chlorine’s discovery to Humphry Davy, who did indeed find it, but thirty-six years after Scheele.

Somewhere in all this, it was thought, there also resided a mysterious élan vital, the force that brought inanimate objects to life. No-one knew where this ethereal essence lay, but two things seemed probable: that you could enliven it with a jolt of electricity (a notion Mary Shelley exploited to full effect in her novel Frankenstein); and that it existed in some substances but not others, which is why we ended up with two branches of chemistry4: organic (for those substances that were thought to have it) and inorganic (for those that did not).

And his fancy equipment did in fact come in very handy. For years, he and Mme Lavoisier occupied themselves with extremely exacting studies requiring the finest measurements. They determined, for instance, that a rusting object doesn’t lose weight, as everyone had long assumed, but gains weight – an extraordinary discovery. Somehow, as it rusted the object was attracting elemental particles from the air. It was the first realization that matter can be transformed but not eliminated.

In the early 1800s there arose in England a fashion for inhaling nitrous oxide, or laughing gas, after it was discovered that its use ‘was attended by a highly pleasurable thrilling11’. For the next half-century it would be the drug of choice for young people.

It wasn’t until 1846 that anyone got around to finding a practical use for nitrous oxide, as an anaesthetic.

It is perhaps telling that one of the most important observations of the century, Brownian motion, which established the active nature of molecules, was made not by a chemist but by a Scottish botanist, Robert Brown. (What Brown noticed13, in 1827, was that tiny grains of pollen suspended in water remained indefinitely in motion no matter how long he gave them to settle. The cause of this perpetual motion – namely, the actions of invisible molecules – was long a mystery.)

Sweden’s J.J. Berzelius brought a much-needed measure of order to matters by decreeing that the elements be abbreviated on the basis of their Greek or Latin names, which is why the abbreviation for iron is Fe (from the Latin ferrum) and for silver is Ag (from the Latin argentum

Mendeleyev was said to have been inspired by the card game known as solitaire in North America and patience elsewhere, wherein cards are arranged by suit horizontally and by number vertically. Using a broadly similar concept, he arranged the elements in horizontal rows called periods and vertical columns called groups.

He noticed that in any sample of radioactive material, it always took the same amount of time for half the sample to decay – the celebrated half-lifefn3 – and that this steady, reliable rate of decay could be used as a kind of clock. By calculating backwards from how much radiation a material had now and how swiftly it was decaying, you could work out its age.

For a long time it was assumed that anything so miraculously energetic as radioactivity must be beneficial. For years, manufacturers of toothpaste and laxatives put radioactive thorium in their products,

Radiation, in fact, is so pernicious and long-lasting that even now her papers from the 1890s – even her cookbooks – are too dangerous to handle.

if you are an average-sized adult you will contain within your modest frame no less than 7 × 1018 joules of potential energy15 – enough to explode with the force of thirty very large hydrogen bombs,

Fly across the

United States and you will step from the plane a quinzillionth of a second, or something, younger than those you left behind.

Spacetime is usually explained by asking you to imagine something flat but pliant – a mattress, say, or a sheet of stretched rubber – on which is resting a heavy round object, such as an iron ball. The weight of the iron ball causes the

material on which it is sitting to stretch and sag slightly.

Now, if you roll a smaller ball across the sheet, it tries to go in a straight line as required by Newton’s laws of motion, but as it nears the massive object and the slope of the sagging fabric, it rolls downwards,

ineluctably drawn to the more massive object. This is gravity – a product of the bending of spacetime.

Astronomers today believe there are perhaps 140 billion galaxies in the visible universe.

The great Caltech physicist Richard Feynman once observed that if you had to reduce scientific history to one important statement it would be: ‘All things are made of atoms

At sea level, at a temperature of 0 degrees Celsius, one cubic centimetre of air (that is, a space about the size of a sugar cube) will contain 45 billion billion molecules2.

Every atom you possess has almost certainly passed through several stars and been part of millions of organisms on its way to becoming you.

We are each so atomically numerous and so vigorously recycled at

death that a significant number of our atoms – up to a billion for each of us, it has been suggested3 – probably once belonged to Shakespeare.

When we die, our atoms will disassemble and move off to find new uses elsewhere – as part of a leaf or other human being or drop of dew.

That’s the scale of an atom: one ten-millionth of a millimetre.

one atom is to that millimetre line above as the thickness of a sheet of paper is to the height of the Empire State Building.

‘We might as well attempt to introduce a new planet into the solar system6 or annihilate one already in existence, as to create or destroy a particle of hydrogen,

Although Dalton tried to avoid all honours, he was elected to the Royal Society against his wishes, showered with medals and given a handsome government pension.

The way it was explained to me is that protons give an atom its identity, electrons its personality.)

It is still a fairly astounding notion to consider that atoms are mostly empty space, and that the solidity we experience all around us is an illusion.

When two objects come together in the real world – billiard balls are most often used for illustration – they don’t actually strike each other. ‘Rather,’ as Timothy Ferris explains, ‘the negatively charged fields of the two balls repel each other … [W]ere it not for their electrical charges they could, like galaxies, pass right through each other unscathed26.’ When you sit in a chair, you are not actually sitting there, but levitating above it at a height of one angstrom (a hundred millionth of a centimetre), your electrons and its electrons implacably opposed to any closer intimacy.

electrons are not like orbiting planets at all, but more like the blades of a spinning fan, managing to fill every bit of space in their orbits simultaneously (but with the crucial difference that the blades of a fan only seem to be everywhere at once; electrons are).

(Because neutrons have no charge, they aren’t repelled by the electrical fields at the heart of an atom and thus could be fired like tiny

torpedoes into an atomic nucleus, setting off the destructive process known as fission.)

As physicists delved deeper, they realized they had found a world not only where electrons could jump from one orbit to another without travelling across any intervening space, but where matter could pop into existence from nothing at all37 – ‘provided’, in the words of Alan Lightman of MIT, ‘it disappears again with sufficient haste.

Wolfgang Pauli’s Exclusion Principle of 1925, that certain pairs of subatomic particles, even when separated by the most considerable distances, can each instantly ‘know’ what the other is doing.

It is as if, in the words of the science writer Lawrence Joseph, you had two identical pool balls38, one in Ohio and the other in Fiji, and that the instant you sent one spinning the other would immediately spin in a contrary direction at precisely the same speed.

physicists at the University of Geneva sent photons seven miles in opposite directions and demonstrated that interfering with one provoked an instantaneous response in the other.

Schrödinger offered a famous thought experiment in which a hypothetical cat was placed in a box with one atom of a radioactive substance attached to a vial of hydrocyanic acid. If the particle degraded within an hour, it would trigger a mechanism that would break the vial and poison the cat. If not, the cat would live. But we could not know which was the case, so there was no choice, scientifically, but to regard the cat as 100 per cent alive and 100 per cent dead at the same time. This means, as Stephen Hawking has observed with a touch of understandable excitement, that one cannot ‘predict future events exactly40 if one cannot even measure the present state of the universe precisely!

Moreover, the idea of action at a distance – that one particle could instantaneously influence another trillions of miles away – was a stark violation of the special theory of relativity. Nothing could outrace the speed of light and yet here were physicists insisting that, somehow, at the subatomic level, information could.

Even though lead was widely known to be dangerous, by the early years of the twentieth century it could be found in all manner of consumer products.

Beneficial ozone is not terribly abundant, however. If it were distributed evenly throughout the stratosphere, it would form a layer just 2 millimetres or so thick. That is why it is so easily disturbed.

A single kilogram of CFCs can capture and annihilate 70,000 kilograms of atmospheric ozone

A single CFC molecule is about ten thousand times more efficient at exacerbating greenhouse effects than a molecule of carbon dioxide

It was based on the realization that all living things have within them an isotope of carbon called carbon-14, which begins to decay at a measurable rate the instant they die. Carbon-14 has a half-life – that is, the time it takes for half of any sample to disappear – of about 5,600 years, so by working out how much of a given sample of carbon had decayed, Libby could get a good fix on the age of an object

Indeed, and rather extraordinarily, we would be well into the space age before anyone could plausibly account for where all the Earth’s old rocks went.

many meteorites are essentially left-over building materials from the early days of the solar system, and thus have managed to preserve a more or less pristine interior chemistry. Measure the age of these wandering rocks and you would have the age also (near enough) of the Earth.

Patterson announced a definitive age for the Earth of 4,550 million years (plus or minus 70 million years)

But because lead is for ever, Americans alive today each have about 625 times more lead in their blood than people did a century ago22

The amount of lead in the atmosphere also continues to grow, quite legally, by about a hundred thousand tonnes a year23, mostly from mining, smelting and industrial activities.

Clair Patterson died in 1995. He didn’t win a Nobel Prize for his work. Geologists never do. Nor, more puzzlingly, did he gain any fame or even much attention from half a century of consistent and increasingly selfless achievement.

Most geology textbooks don’t mention him. Two recent popular books on the history of the dating of the Earth actually manage to misspell his name

C. T. R. Wilson

Back in the Cavendish Lab in Cambridge he built an artificial cloud chamber – a simple device in which he could cool and moisten the air, creating a reasonable model of a cloud in laboratory conditions. The device worked very well, but had an additional, unexpected benefit. When he accelerated an alpha particle through the chamber to seed his make-believe clouds, it left a visible trail – like the contrails of a passing airliner. He had just invented the particle detector.

Using huge amounts of energy (some operate only at night so that people in neighbouring towns don’t have to witness their lights fading when the apparatus is fired up), they can whip particles into such a state of liveliness that a single electron can do 47,000 laps around a 7-kilometre tunnel in under a second

Every second the Earth is visited by ten thousand trillion trillion tiny, all-but-massless neutrinos (mostly shot out by the nuclear broilings of the Sun) and virtually all of them pass right through the planet and everything that is on it, including you and me, as if it weren’t there. To trap just a few of them, scientists need tanks holding up to 57,000 cubic metres of heavy water (that is, water with a relative abundance of deuterium in it) in underground chambers (old mines, usually) where they can’t be interfered with by other types of radiation. Very occasionally, a passing neutrino will bang into one of the atomic nuclei in the water and produce a little puff of energy.

Breaking up atoms, as James Trefil has noted, is easy6; you do it each time you switch on a fluorescent light. Breaking up atomic nuclei, however, requires quite a lot of money and a generous supply of electricity. Getting down to the level of quarks – the particles that make up particles – requires still more: trillions of volts of electricity and the budget of a small Central American state.

Carl Sagan in Cosmos raised the possibility that if you travelled downwards into an electron, you might find that it contained a universe of its own, recalling all those science-fiction stories of the 1950s. ‘Within it, organized into the local equivalent of galaxies and smaller structures, are an immense number of other, much tinier elementary particles, which are themselves universes at the next level and so on forever13 – an infinite downward regression, universes within universes, endlessly. And upward as well.

The arrangement essentially is that among the basic building blocks of matter are quarks; these are held together by particles called gluons; and together quarks and gluons form protons and neutrons, the stuff of the atom’s nucleus.

Leptons are the source of electrons and neutrinos.

As Donald Goldsmith notes, when astronomers say that the galaxy M87 is 60 million light years away, what they really mean37 (‘but do not often stress to the general public’) is that it is somewhere between 40 million and 90 million light years away – not quite the same thing.

It appears that at least 90 per cent of the universe, and perhaps as much as 99 per cent, is composed of Fritz Zwicky’s ‘dark matter’ – stuff that is by its nature invisible to us. It is slightly galling to think that we live in a universe that for the most part we can’t even see, but there you are.

DUNNOS (for Dark Unknown Nonreflective Nondetectable Objects Somewhere).

Recent evidence suggests not only that the galaxies of the universe are racing away from us, but that they are doing so at a rate that is accelerating. This is counter to all expectations. It appears that the universe may be filled not only with dark matter, but with dark energy. Scientists sometimes also call it vacuum energy or quintessence.

The upshot of all this is that we live in a universe whose age we can’t quite compute, surrounded by stars whose distances from us and each other we don’t altogether know, filled with matter we can’t identify, operating in conformance with physical laws whose properties we don’t truly understand.

Kazakhstan, it turns out, was once attached to Norway and New England.

Pick up a pebble from a Massachusetts beach and its nearest kin will now be in Africa.

Thanks to Global Positioning Systems we can see

that Europe and North America are parting at about the speed a fingernail grows16 – roughly two metres in a human lifetime.

No-one can say what causes the oceans’ chemistry to change so dramatically from time to time, but the opening and shutting of ocean ridges would be an obvious possible culprit.

Manson crater.

‘Suppose that there was a button you could push and you could light up all the Earth-crossing asteroids larger than about ten metres, there would be over a hundred million of these objects in the sky.

In the early 1970s, Walter Alvarez was doing fieldwork in a comely defile known as the Bottaccione Gorge, near the Umbrian hill town of Gubbio, when he grew curious about a thin band of reddish clay that divided two ancient layers of limestone – one from the Cretaceous period, the other from the Tertiary. This is a point known to geology as the KT boundaryf1 and it marks the time, 65 million years ago, when the dinosaurs and roughly half the world’s other species of animals abruptly vanish from the fossil record. Alvarez wondered what it was about a thin lamina of clay, barely 6 millimetres thick, that could account for such a dramatic moment in the Earth’s history.

Tom Gehrels, an asteroid hunter at the University of Arizona, thinks that even a year’s warning would probably be insufficient33 to take appropriate action. The greater likelihood, however, is that we wouldn’t see any object – even a comet – until it was about six months away, which would be much too late.

The distance from the surface of Earth to the middle is 6,370 kilometres4, which isn’t so very far.

most mines on Earth go no more than about 400 metres beneath the surface.

The scale is, of course, more an idea than a thing, an arbitrary measure of the Earth’s tremblings based on surface measurements. It rises exponentially6, so that a 7.3 quake is ten times more powerful than a 6.3 earthquake and 100 times more powerful than a 5.3 earthquake.

Tokyo stands on the meeting point of three tectonic plates in a country already well known for its seismic instability.

We know a little bit about the mantle from what are known as kimberlite pipes14, where diamonds are formed. What happens is that deep in the Earth there is an explosion that fires, in effect, a cannonball of magma to the surface at supersonic speeds. It is a totally random event. A kimberlite pipe could explode in your back garden as you read this. Because they come up from such depths – up to 200 kilometres down – kimberlite pipes bring up all kinds of things not normally found on or near the surface: a rock called peridotite, crystals of olivine and – just occasionally, in about one pipe in a hundred – diamonds.

Scientists are generally agreed15 that the world beneath us is composed of four layers – a rocky outer crust, a mantle of hot, viscous rock, a liquid outer core and a solid inner core.

It may not look it, but all the glass on Earth is flowing downwards under the relentless drag of gravity.

Remove a pane of really old glass from the window of

a European cathedral and it will be noticeably thicker at the bottom than at the top.

Beneath the mantle are the two cores, a solid inner core and a liquid outer one.

They know that the pressures at the centre of the Earth are sufficiently high – something over three million times those found at the surface23 – to turn any rock there solid.

The theory was put forward by E. C. Bullard of Cambridge University in 1949 that this fluid part of the Earth’s core revolves in a way that makes it, in effect, an electrical motor, creating the Earth’s magnetic field.

Bodies that don’t have a liquid core – the Moon and Mars, for instance – don’t have magnetism.

Altogether in the last hundred million years it has reversed itself about two hundred times, and we don’t have any real idea why. This has been called ‘the greatest unanswered question in the geological sciences

Any diminution in magnetism is likely to be bad news, because magnetism, apart from holding notes to refrigerators and keeping our compasses pointing the right way, plays a vital role in keeping us alive. Space is full of dangerous cosmic rays which, in the absence of magnetic protection, would tear through our bodies, leaving much of our DNA in useless shreds. When the magnetic field is working, these rays are safely herded away from the Earth’s surface and into two zones in near space called the Van Allen belts. They also interact with particles in the upper atmosphere to create the bewitching veils of light known as the auroras.

In 1943 at Paricutín in Mexico1 a farmer was startled to see smoke rising from a patch on his land. In one week he was the bemused owner of a cone 152 metres high. Within two years it had topped out at almost 430 metres and was more than 800 metres across.

But there is a second, less celebrated type of volcano that doesn’t involve mountain-building. These are volcanoes so explosive that they burst open in a single mighty rupture, leaving behind a vast subsided pit, the caldera (from a Latin word for cauldron).

The upper limit for life is thought to be about

120 degrees Celsius, though no-one actually knows.

The more I examine the universe and study the details of its architecture, the more evidence I find that the universe in some sense must have known we were coming

It isn’t simply that we can’t breathe in water, but that we couldn’t bear the pressures. Because water is about 1,300 times heavier than air2, pressures rise swiftly as you descend – by the equivalent of one atmosphere for every 10 metres of depth.

Most oceans are of course much shallower, but even at the average ocean depth of 4 kilometres the pressure is equivalent to being squashed beneath a stack of fourteen loaded cement trucks

The air we breathe is 80 per cent nitrogen. Put the human body under pressure, and that nitrogen is transformed into tiny bubbles that migrate into the blood and tissues. If the pressure is changed too rapidly – as with a too-quick ascent by a diver – the bubbles trapped within the body will begin to fizz in exactly the manner of a freshly opened bottle of champagne, clogging tiny blood vessels, depriving cells of oxygen and causing pain so excruciating that sufferers are prone to bend double in agony – hence ‘the bends

For reasons that are still poorly understood, at depths beyond about 30 metres nitrogen becomes a powerful intoxicant.

It is a curiosity of physics that the larger a star is, the more rapidly it burns. Had our sun been ten times as massive, it would have exhausted itself after ten million years instead of ten billion23 and we wouldn’t be here now.

In 1978, an astrophysicist named Michael Hart made some calculations and concluded that the Earth would have been uninhabitable had it been just 1 per cent further from or 5 per cent closer to the Sun. That’s not much, and in fact it wasn’t enough. The figures have since been refined and made a little more generous – 5 per cent nearer and 15 per cent further are thought to be more accurate assessments for our zone of habitability – but that is still a narrow belt.

Apart from much else, our lively interior created the outpourings of gas that helped to build an atmosphere and provided us with the magnetic field that shields us from cosmic radiation. It also gave us plate tectonics, which continually renews and rumples the surface.

Without the Moon’s steadying influence, the Earth would wobble like a dying top, with goodness knows what consequences for climate and weather. The

Moon’s steady gravitational influence keeps the Earth spinning at the right speed and angle to provide the sort of stability necessary for the long and successful development of life. This won’t go on for ever. The Moon is slipping from our grasp at a rate of about 4 centimetres a year27

about 4.4 billion years ago a Mars-sized object slammed into Earth, blowing out enough material to create the Moon from the debris.

There are ninety-four naturally occurring elements on the Earth, plus a further twenty-three or so that have been created in labs,

silicon is the second most common element on the Earth, or that titanium is tenth?

Aluminium is the fourth most common element on Earth,

Carbon is only the fifteenth most common element,

Of every 200 atoms in your body, 126 are hydrogen, 51 are oxygen, and just 19 are carbon

We need iron to manufacture haemoglobin, and without it we would die. Cobalt is necessary for the creation of vitamin B12. Potassium and a very little sodium are literally good for your nerves. Molybdenum, manganese and vanadium

help to keep your enzymes purring. Zinc – bless it – oxidizes alcohol.

The degree to which organisms require or tolerate certain elements is a relic of their evolution

When elements don’t occur naturally on Earth, we have evolved no tolerance for them and so they tend to be extremely toxic to us, as with plutonium.

Temperature is really just a measure of the activity of molecules. At sea level, air molecules are so thick that one molecule can move only the tiniest distance – about eight-millionths of a centimetre, to be precise6 – before banging into another. Because trillions of molecules are constantly colliding, a lot of heat gets exchanged. But at the height of the thermosphere, at 80 kilometres or more, the air is so thin that any two molecules will be miles apart and hardly ever come into contact. So although each molecule is very warm, there are few interactions between them and thus little heat transference.

Although the atmosphere is very thin, if a craft comes in at too steep an angle – more than about 6 degrees – or too swiftly it can strike enough molecules to generate drag of an exceedingly combustible nature. Conversely, if an incoming vehicle hit the thermosphere at too shallow an angle, it could well bounce back into space7, like a pebble skipped across water.

In The Other Side of Everest, the British mountaineer and film-maker Matt Dickinson records how Howard Somervell, on a 1924 British expedition up Everest, ‘found himself choking to death after a piece of infected flesh came loose and blocked his windpipe8’. With a supreme effort Somervell managed to cough up the obstruction. It turned out to be ‘the entire mucous lining of his larynx

Bodily distress is notorious above 7,500 metres – the area known to climbers as the Death Zone – but many people become severely debilitated, even dangerously ill, at heights of no more than 4,500

metres or so.

Sunlight energizes atoms. It increases the rate at which they jiggle and jounce, and in their enlivened state they crash into one another, releasing heat.

Altogether there are about 5,200 million million tonnes of air around us – 25 million tonnes for every square mile of the planet – a not inconsequential volume. When you get millions of tonnes of atmosphere rushing past at 50

or 60 kilometres an hour, it’s hardly a surprise that tree-limbs snap and roof tiles go flying.

One thunderstorm, it has been calculated, can contain an amount of energy equivalent to four days’ use of electricity for the whole United States

A bolt of lightning travels at 435,000 kilometres an hour and can heat the air around it to a decidedly crisp 28,000 degrees Celsius, several times hotter than the surface of the sun.

A form of wave motion popularly known as clear-air turbulence occasionally enlivens aeroplane flights. About twenty such incidents a year are serious enough to need reporting. They are not associated with cloud structures or anything else that can be detected visually or by radar. They are just

pockets of startling turbulence in the middle of tranquil skies.

For instance, stratus clouds – those unlovable, featureless sprawls that give us our overcast skies – happen when moisture-bearing updrafts lack the oomph to break through a level of more stable air above, and instead spread out, like smoke hitting a ceiling. Indeed, if you watch a smoker sometime, you can get a very good idea of how things work by watching how smoke rises from a cigarette in a still room. At first, it goes straight up (this is called a laminar flow if you need to impress anyone) and then it spreads out in a diffused, wavy layer.

What we do know is that because heat from the Sun is unevenly distributed, differences in air pressure arise on the planet. Air can’t abide this, so it rushes around trying to equalize things everywhere. Wind is simply the air’s way of trying to keep things in balance.

A tropical hurricane can release in twenty-four hours as much

energy as a rich, medium-sized nation like Britain or France uses in a year17

The Earth revolves at a brisk 1,675 kilometres an hour at the equator, though as you move towards the poles the speed slopes off considerably, to about 900 kilometres an hour in

London or Paris, for instance.

Once evaporated, they spend no more than a week or so – Drury says twelve days – in the sky before falling again as rain.

Water is marvellous at holding and transporting heat – unimaginably vast quantities of it. Every day, the Gulf Stream carries an amount of heat to Europe equivalent to the world’s output of coal for ten years30, which is why Britain and Ireland have such mild winters compared with Canada and Russia.

The seas do one other great favour for us. They soak up tremendous volumes of carbon and provide a means for it to be safely locked away. One of the oddities of our solar system is that the Sun burns about 25 per cent more brightly now than when the solar system was young. This should have resulted in a much warmer Earth.

So what keeps the planet stable and cool? Life does. Trillions upon trillions of tiny marine organisms that most of us have never heard of – foraminiferans and coccoliths and calcareous algae – capture atmospheric carbon, in the form of carbon dioxide, when it falls as rain and use it (in combination with other things) to make their tiny shells. By locking the carbon up in their shells, they

keep it from being re-evaporated into the atmosphere where it would build up dangerously as a greenhouse gas. Eventually all the tiny foraminiferans and coccoliths and so on die and fall to the bottom of the sea, where they are compressed into limestone.

Eventually much of that limestone will end up feeding volcanoes and the carbon will return to the atmosphere and fall to the Earth in rain, which is why the whole is called the long-term carbon cycle. The process takes a very long time – about half a million years for a typical carbon atom – but in the absence of any other disturbance it works

remarkably well at keeping the climate stable.

‘There is a critical threshold where the natural biosphere stops buffering us from the effects of our emissions and actually starts to amplify them.’ The fear is that there would be a very rapid increase in the Earth’s warming. Unable to adapt, many trees and other plants would die, releasing their stores of carbon and adding to the problem.

Most liquids when chilled contract by about 10 per cent. Water does too, but only down to a point. Once it is within whispering distance of freezing, it begins – perversely, beguilingly, extremely improbably – to

expand. By the time it is solid, it is almost a tenth more voluminous than it was before4. Because it expands, ice floats on water

The hydrogen atoms cling fiercely to their oxygen host, but also make casual bonds with other water molecules. The nature of a water molecule means that it engages in a kind of dance with other water molecules, briefly pairing and then moving on, like the ever-changing partners in a quadrille6, to use Robert Kunzig’s nice phrase. A glass

of water may not appear terribly lively, but every molecule in it is changing partners billions of times a second. That’s why water molecules stick together to form bodies like puddles and lakes, but not so tightly that they can’t be easily separated as when, for instance, you dive into a pool of them.

In one sense the bond is very strong – it is why water molecules can flow uphill when siphoned and why water droplets on a car bonnet show such a singular determination to bead with their partners. It is also why water has surface tension. The molecules at the surface are attracted more powerfully to the like molecules beneath and beside them than to the air molecules above. This creates a sort of membrane strong enough to support insects and skipping stones.

There are 1.3 billion cubic kilometres of water on Earth and that is all we’re ever going to get11. The system is closed: practically speaking, nothing can be added or subtracted.

We have better maps of Mars than we do of our own seabeds.

A typical submersible costs about \$25,000 a day to operate, so they are hardly dropped into the water on a whim, still less put to sea in the hope that they will randomly stumble on something of interest.

It had been known for centuries that rivers carry minerals to the sea and that these

minerals combine with ions in the ocean water to form salts. So far no problem. But what was puzzling was that the salinity levels of the sea were stable. Millions of gallons of fresh water evaporate from the ocean daily, leaving all their salts behind, so logically the seas ought to grow more salty with the passing years, but they don’t. Something takes an amount of salt out of the water equivalent to the amount being put in. For a very long time, no-one could figure out what could be responsible for this. Alvin’s discovery of the deep-sea vents provided the answer.

As water is taken down into the Earth’s crust, salts are stripped from it, and eventually clean water is blown out again through the chimney stacks. The process is not swift – it can take up to ten million years to clean an ocean

Yet no scientist – no person, as far as we know – has ever seen a giant squid alive. Zoologists have devoted careers to trying to capture, or just glimpse, living giant squid and have always failed. They are known mostly from being washed up on beaches – particularly, for unknown reasons, the beaches of the South Island of New Zealand.

The World Wildlife Fund estimated in 1994 that the number of sharks killed each year was between 40 million and 70 million.

Perhaps as much as 22 million tonnes of such unwanted fish are dumped back in the sea each year, mostly in the form of corpses44. For every kilogram of shrimp harvested, about four kilograms of fish and other marine creatures are destroyed.

The southern oceans around Antarctica52 produce only about 3 per cent of the world’s phytoplankton – far too little, it would seem, to support a complex ecosystem, and yet they do. Crab-eater seals are not a species of animal that most of us have heard of, but they may actually be the second most numerous large species of animal on Earth, after humans. As many as 15 million of them may live on the pack ice around Antarctica.

In 1953 Stanley Miller, a graduate student at the University of Chicago, took two flasks – one containing a little water to represent a primeval ocean, the other holding a mixture of methane, ammonia and hydrogen sulphide gases to represent the Earth’s early atmosphere – connected them with rubber tubes and introduced some electrical sparks as a stand-in for lightning. After a few days, the water in the flasks had turned green and yellow in a hearty broth of amino acids1, fatty acids, sugars and other organic compounds.

Proteins are what you get when you string amino acids together, and we need a lot of them. No-one really knows, but there may be as many as a million types of protein in the human body3, and each one is a little miracle. By all the laws of probability proteins shouldn’t exist. To make a protein you need to assemble amino acids (which I am obliged by long tradition to refer to here as ‘the building blocks of life’) in a particular order, in much the same way that

you assemble letters in a particular order to spell a word.

To make collagen, you need to arrange 1,055 amino acids in precisely the right sequence. But – and here’s an obvious but crucial point – you don’t make it. It makes itself, spontaneously, without direction, and this is where the unlikelihoods come in.

To be of use, a protein must not only assemble amino acids in the right sequence, it must then engage in a kind of chemical origami and fold itself into a very specific shape. Even having achieved

this structural complexity, a protein is no good to you if it can’t reproduce itself, and proteins can’t. For this you need DNA. DNA is a whiz at replicating – it can make a copy of itself in seconds6 – but can do virtually nothing else. So we have a paradoxical situation. Proteins can’t exist without DNA and DNA has no purpose without proteins. Are we to assume, then, that they arose simultaneously with the purpose of supporting each other? If so: wow. And there is more still. DNA, proteins and the other components of life couldn’t prosper without some sort of membrane to contain them. No atom or molecule has ever achieved life independently. Pluck any atom from your body and it is no more alive than is a grain of sand. It is only when they come together within the nurturing refuge of a cell that these diverse materials can take part in the amazing dance that we call life. Without the cell, they are nothing more than interesting chemicals. But without the chemicals, the cell has no purpose. As Davies puts it, ‘If everything needs everything else, how did the community of molecules ever arise in the first place7?

As Richard Dawkins argues in The Blind Watchmaker, there must have been some kind of cumulative selection process that allowed amino acids to assemble8 in chunks. Perhaps two or three amino acids linked up for some simple purpose and then after a time bumped into some other similar small cluster and in so doing ‘discovered’ some additional improvement.

Lots of molecules in nature get together to form long chains called polymers9. Sugars constantly assemble to form starches. Crystals can do a number of lifelike things – replicate, respond to environmental stimuli, take on a patterned complexity.

If you wished to create another living object, whether a goldfish or a head of lettuce or a human being, you would need really only four principal elements11, carbon, hydrogen, oxygen and nitrogen, plus small amounts of a few others, principally sulphur, phosphorus, calcium and iron. Put these together in three dozen or so combinations to form some sugars, acids and other basic

compounds and you can build anything that lives. As Dawkins notes: ‘There is nothing special about the substances from which living things are made12. Living things are collections of molecules, like everything else.

The actual chemistry of all this is a little arcane for our purposes here, but it is enough to know that if you make monomers wet they don’t turn into polymers – except when creating life on the Earth. How and why it happens then and not otherwise is one of biology’s great unanswered questions.

Halley’s comet, it is now thought, is about 25 per cent organic molecules. Get enough of those crashing into a suitable place – Earth, for instance – and you have the basic elements you need for life.

Whatever prompted life to begin, it happened just once. That is the most extraordinary fact in biology, perhaps the most extraordinary fact we know.

We are all the result of a

single genetic trick handed down from generation to generation over nearly four billion years, to such an extent that you can take a fragment of human genetic instruction and patch it into a faulty yeast cell and the yeast cell will put it to work as if it were its own. In a very real sense, it is its own.

If you were to step from a time machine into that ancient Archaean world, you would very swiftly scamper back inside, for there was no more oxygen to breathe on the Earth back then than there is on Mars today. It was also full of noxious vapours from hydrochloric and sulphuric acids powerful enough to eat through clothing and blister skin23

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.

Our white blood cells actually use oxygen to kill invading bacteria25

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 phenomenon vividly recorded in the banded iron deposits that provide so much of the world’s iron ore today.

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.

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 complex chapter in life’s history.

It took about two billion years, roughly 40 per cent of Earth’s history, for oxygen levels to reach more or less modern levels of concentration in the atmosphere. But 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.) 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.

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.

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.

Your digestive system alone is host to more than a hundred trillion microbes, of at least four hundred types3

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.

Clostridium perfringens, the disagreeable little organism that causes gangrene, can reproduce in nine minutes8 and then begin at once to split again. At such a rate, a single bacterium could theoretically produce more offspring in two days than there are protons in the universe

‘Given an adequate supply of nutrients, a single bacterial cell can generate 280,000 billion individuals in a single day

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.

They have been found living in boiling mud pots and lakes of caustic soda, deep inside rocks, at the bottom of the sea, in hidden pools of icy water in the McMurdo Dry Valleys of Antarctica, and 11 kilometres down in the Pacific Ocean where pressures are more than a thousand times greater than at the surface, or equivalent to being squashed beneath fifty jumbo jets. Some of them seem to be practically indestructible. Deinococcus radiodurans is, according to The Economist, ‘almost immune to radioactivity’. Blast its DNA with radiation and the pieces immediately re-form ‘like the scuttling limbs of an undead creature from a horror movie14’. Perhaps the most extraordinary survival yet found

was that of a Streptococcus bacterium that was recovered from the sealed lens of a camera that had stood on the Moon for two years

Considering how wildly adaptable they are in nature, it is an odd fact that the one place they seem not to wish to live is a petri dish.

It is a natural human impulse to think of evolution as a long chain of improvements, of a never-ending advance towards largeness and complexity – in a

word, towards us. We flatter ourselves. Most of the real diversity in evolution has been small-scale. We large things are just flukes – an interesting side branch.

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.

A great deal of sickness arises not because of what the organism has done to you but because of what your body is trying to do to the organism. In its quest to rid the body of pathogens, the immune system sometimes destroys cells or damages critical tissues, so often when you are unwell what you are feeling is not the pathogens but your own immune responses.

One of the odder aspects of infection is that microbes that normally do no harm at all sometimes get into the wrong parts of the body and ‘go kind of crazy

‘It happens all the time with car accidents when people suffer internal injuries. Microbes that are normally benign

in the gut get into other parts of the body – the bloodstream, for instance – and cause terrible havoc.

Remarkably, by one estimate some 70 per cent of the antibiotics used in the developed world are given to farm animals, often routinely in stock feed, simply to promote growth or as a precaution against infection. Such applications give bacteria every opportunity to evolve a resistance to them. It is an opportunity that they have enthusiastically seized.

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.

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.

Viruses prosper by hijacking the genetic material of a living cell, and using it to produce more virus.

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.

Only about 15 per cent of rocks can preserve fossils

Only about one bone in a billion, it is thought, ever becomes fossilized.

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.

the fact is that there is one other extremely pertinent quality about life on Earth: it goes extinct. Quite regularly. For all the trouble they take to assemble and preserve themselves, species crumple and die remarkably routinely. And the more complex they get, the more quickly they appear to go extinct. Which is perhaps one reason why so much of life isn’t terribly ambitious.

In fact, the first visible mobile residents on dry land were probably much more like modern woodlice, sometimes also known as pillbugs or sow bugs. These are the little bugs (crustaceans, in fact) that are commonly thrown into confusion when you upturn a rock or log.

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.

Each of these massive transformations, as well as many smaller ones between and since, was dependent on that paradoxically important motor of

progress: extinction. It is a curious fact that on Earth species death is, in the most literal sense, a way of life.

A typical solar flare – something we wouldn’t even notice on Earth – will release the energy equivalent of a billion hydrogen bombs and fling into space 100 billion tonnes or so of murderous high-energy particles. The magnetosphere and atmosphere between them normally swat these back

into space or steer them safely towards the poles (where they produce the Earth’s comely auroras), but it is thought that an unusually big blast, say a hundred times the typical flare, could overwhelm our ethereal defences.

Such an outburst is not easily imagined26, but, as James Lawrence Powell has pointed out, if you exploded one Hiroshima-sized bomb for every person alive on Earth today you would still be about a billion bombs short of the size of the KT impact. Yet even that alone may not have been enough to wipe out 70 per cent of Earth’s life, dinosaurs included.

Consider dinosaurs. Museums give the impression that we have a global abundance of dinosaur fossils. In fact, overwhelmingly museum displays are artificial.

We are so used to the notion of our own inevitability as life’s dominant species that it is hard to grasp that we are here only because of timely extraterrestrial bangs and other random flukes.

Plant collecting in the eighteenth century became a kind of international mania. Glory and wealth alike awaited those who could find new species, and botanists and adventurers went to the most incredible lengths to satisfy the world’s craving for horticultural novelty.

In a well-known exercise in the 1980s, Terry Erwin of the Smithsonian Institution saturated a stand of nineteen rainforest trees in Panama with an insecticide fog, then collected everything that fell into his nets from the canopy. Among his haul

(actually hauls, since he repeated the experiment seasonally to make sure he caught migrant species) were twelve hundred types of beetle.

In practical terms, this is not always a bad thing. You might not slumber quite so contentedly if you were aware that your mattress is home to perhaps two million microscopic mites26, which come out in the wee hours to sup on your sebaceous oils and feast on all those lovely, crunchy flakes of skin that you shed as you doze and toss.

Indeed, if your pillow is six years old – which is apparently about the average age for a pillow – it has been estimated that one tenth of its weight will be made up of ‘sloughed skin, living mites, dead mites and mite dung

Go out into the woods – any woods at all – bend down and scoop up a handful of soil, and you will be holding up to ten billion bacteria, most of them unknown to science.

At least 99 per cent of flowering plants have never been tested for their medicinal properties. Because they can’t flee from predators, plants have had to contrive elaborate chemical defences, and so are particularly rich in intriguing compounds. Even now, nearly a quarter of all prescribed medicines are derived from just forty plants, with another 16 per cent coming from

animals or microbes, so there is a serious risk with every hectare of forest felled of losing medically vital possibilities.

In the 1980s, amateur cave explorers entered a deep cave in Romania that had been sealed off from the outside world for a long but unknown period and found thirty-three species of insects and other small creatures – spiders, centipedes, lice – all blind, colourless and new to science. They were living off the microbes in the surface scum of pools, which in turn were feeding on hydrogen sulphide from hot springs.

you have 140,000 trillion (140,000,000,000,000,000) cells in your body and are ready to spring forth as a human being.fn1 And every one of those cells knows exactly what to do to preserve and nurture you from the moment of conception to your last breath. You have no secrets from your cells. They know far more about you than you do. Each one carries a copy of the complete genetic code – the instruction manual for your body – so it knows how to do not only its own job but every other job in the body too.

To build the most basic yeast cell, for example, you would have to miniaturize about the same number of components as are found in a Boeing 777 jetliner1 and fit them into a sphere just 5 microns across; then somehow you would have to persuade that sphere to reproduce.

In nature, nitric oxide is a formidable toxin and a common component of air pollution. So scientists were naturally a little surprised when, in the mid-1980s, they found it being produced in a curiously devoted manner in human cells. Its purpose was at first a mystery, but then scientists began to find it all over the place3 – controlling the flow of blood and the energy levels of cells, attacking cancers and other pathogens, regulating the sense of smell, even assisting in penile erections. It also explained why

nitroglycerine, the well-known explosive, soothes the heart pain known as angina.

If you are an average-sized adult you are lugging around over 2 kilograms of dead skin6, of which several billion tiny fragments are sloughed off each day. Run a finger along a dusty shelf and you are drawing a pattern very largely in old skin.

Brain cells last as long as you do. You are issued with a hundred billion or so at birth and that is all you are ever going to get.

Indeed, it has been suggested that there

isn’t a single bit of any of us – not so much as a stray molecule8 – that was part of us nine years ago. It may not feel like it, but at the cellular level we are all youngsters.

What Leeuwenhoek had found

were protozoa. He calculated that there were 8,280,000 of these tiny beings in a single drop of water11 – more than the number of people in Holland.

To begin with there is no up or down inside the cell (gravity doesn’t meaningfully apply at the cellular scale), and not an atom’s width of space is unused. There is activity everywhere and a ceaseless thrum of electrical energy. You may not feel terribly electrical, but you are. The food we eat and the oxygen we breathe are combined in the cells into electricity. The reason we don’t give each other massive shocks or scorch the sofa when we sit down is that it is all happening on a tiny scale: a mere 0.1 volts travelling distances measured in nanometres.

You can see that a cell is just millions of objects – lysosomes, endosomes, ribosomes, ligands, peroxisomes, proteins of every size and shape – bumping into millions of other objects and performing mundane tasks: extracting energy from nutrients, assembling structures, getting rid of waste, warding off intruders, sending and receiving messages, making repairs. Typically a cell will contain some twenty thousand different types of protein, and of these about two thousand types will each be represented by at least fifty thousand molecules.

heart must pump 343 litres of blood an hour, over 8,000 litres every day, 3 million litres in a year – that’s enough to fill four Olympic-sized swimming pools – to keep all those cells freshly oxygenated.

The oxygen is taken up by the mitochondria. These are the cells’ power stations and there are about a thousand of them in a typical cell, though the number varies considerably depending on what a cell does and how much energy it requires.

Virtually all the food and oxygen you take into your body are delivered, after processing, to the mitochondria, where they are converted into a molecule called adenosine tri-phosphate, or ATP.

ATP molecules are essentially little battery packs that move through the cell providing energy for all the cell’s processes, and you get through a lot of it. At any given moment, a typical cell in your body will have about one billion ATP molecules in it21, and in two minutes every one of them will have been drained dry and another billion will have taken their place. Every day you produce and use up a volume of ATP equivalent to about half your body weight22. Feel the warmth of your skin. That’s your ATP at work.

Every day billions of your cells die for your benefit and billions of others clean up the mess. Cells can also die violently – for instance, when infected – but mostly they die because they are told to. Indeed, if not told to live – if not given some kind of active instruction from another cell – cells automatically kill themselves. Cells need a lot of reassurance.

When, as occasionally happens, a cell fails to expire in the prescribed manner, but rather begins to divide and proliferate wildly, we call the result cancer. Cancer cells are really just confused cells. Cells make this mistake fairly regularly, but the body has elaborate mechanisms for dealing with it. It is only very rarely that the process spirals out of control. On average, humans suffer one fatal malignancy for each 100 million billion cell divisions23. Cancer is bad luck in every possible sense of the term.

In ways that we have barely begun to understand, trillions upon trillions of reflexive chemical reactions add up to a mobile, thinking, decision-making you – or, come to that, a rather less reflective but still incredibly organized dung beetle. Every living thing, never forget, is a wonder of atomic engineering.

Darwin was invited to sail on the naval survey ship HMS Beagle, essentially as dinner company for the captain, Robert FitzRoy, whose rank precluded his socializing with anyone other than a gentleman. FitzRoy, who was very odd, chose Darwin in part because he liked the shape of Darwin’s nose.

At the time of the Beagle voyage, Darwin was fresh out of university and not yet an accomplished naturalist, and so failed to see that the Galápagos birds were all of a type. It was his friend the ornithologist John Gould9 who realized that what Darwin had found was lots of finches with different talents.

Darwin kept his theory to himself because he well knew the storm it would cause. In 1844, the year he locked his notes away, a book called Vestiges of the Natural History of Creation roused much of the thinking world to fury by suggesting that humans might have evolved from lesser primates without the assistance of a divine creator.

Much less amenable to Darwin’s claim of priority was a Scottish gardener named Patrick Matthew17 who had, rather remarkably, also come up with the principles of natural selection more than twenty years earlier – in fact, in the very year that Darwin had set sail in the Beagle

Together, without realizing it, Darwin and Mendel laid the groundwork for all of life sciences in the twentieth


It is fairly amazing to reflect that at the beginning of the twentieth century, and for some years beyond, the best scientific minds in the world couldn’t actually tell you, in any meaningful way, where babies came from.

If you go back sixty-four generations, to the time of the Romans, the number of people on whose co-operative efforts your eventual existence depends has risen to approximately one million trillion, which is several thousand times the total number of people who have ever lived. Clearly something has gone wrong with our maths here. The answer, it may interest you to learn, is that your line is not pure. You couldn’t be here without a little incest – actually quite a lot of incest – albeit at a genetically discreet remove.

We are also uncannily alike. Compare your genes with any other human being’s and on average they will be about 99.9 per cent the same. That is what makes us a species. The tiny differences in that remaining 0.1 per cent – ‘roughly one nucleotide base in every thousand1’, to quote the British geneticist and recent Nobel laureate John Sulston – are what endow us with our individuality.

Inside the cell is a nucleus and inside each nucleus are the chromosomes – forty-six little bundles of complexity, of which twenty-three come from your mother and twenty-three from your father. With a very few exceptions, every cell in your body – 99.999 per cent of them, say – carries the same complement of chromosomes.

DNA exists for just one reason – to create more DNA – and you have a lot of it inside you: nearly 2 metres of it squeezed into almost every cell. Each length of DNA comprises some 3.2 billion letters of coding, enough to provide 101,920,000,000 possible combinations, ‘guaranteed to be unique against all conceivable odds3’, in the words of Christian de Duve. That’s a lot of possibility – a one followed by more than three billion zeroes.

Altogether, according to one calculation, you may have as much as 20 billion kilometres of DNA bundled

up inside you

No molecule is, but DNA is, as it were, especially unalive. It is ‘among the most nonreactive, chemically inert molecules6 in the living world’, in the words of the geneticist Richard Lewontin. That is why it can be recovered from patches of long-dried blood or semen in murder investigations and coaxed from the bones of ancient Neandertals.

Working with a kind of chemical clerk called a ribosome, RNA translates information from a cell’s DNA into terms proteins can understand and act upon.

Finally, in 1944, after fifteen years of effort, a team at the Rockefeller Institute in Manhattan, led by a brilliant but diffident Canadian named Oswald Avery, succeeded with an exceedingly tricky experiment in which an innocuous strain of bacteria was made permanently infectious by crossing it with alien DNA, proving that DNA was far more than a passive molecule and almost certainly was the active agent in heredity.

Crystallography had been used successfully to map atoms in crystals (hence ‘crystallography’), but DNA molecules were a much more finicky proposition.

It was known that DNA had four chemical components – called adenine, guanine, cytosine and thiamine – and that these paired up in particular ways. By playing with pieces of cardboard cut into the shapes of molecules, Watson and Crick were able to work out how the pieces fit together.

The 25 April 1953 edition of Nature carried a 900-word article by Watson and Crick titled ‘A Structure for Deoxyribose Nucleic Acid23’. Accompanying it were separate articles by Wilkins and Franklin. It was an eventful time in the world – Edmund Hillary was just about to clamber to the top of Everest, while Elizabeth II was shortly to be crowned Queen – so the discovery of the secret of life was mostly overlooked. It received a small mention in the News Chronicle and was ignored elsewhere

Ninety-seven per cent of your DNA consists of nothing but long stretches of meaningless garble – ‘junk’ or ‘non-coding DNA’ as biochemists prefer to put it. Only here and there along each strand do you find sections that control and organize vital functions. These are the curious and long-elusive genes. Genes are nothing more (nor less) than instructions to make proteins. This they do with a certain dull fidelity. In this sense, they are rather like the keys of a piano, each playing a single note and nothing else28, which is obviously a trifle monotonous. But combine the genes, as you would combine piano keys, and you can create chords and melodies of infinite variety. Put all these genes together and you have (to continue the metaphor) the great symphony of existence known as the human genome. An alternative and more common way to regard the genome is as a kind of instruction manual for the body. Viewed this way, the chromosomes can be imagined as the book’s chapters and the genes as individual instructions for making proteins. The words in which the instructions are written are called codons and the

letters are known as bases. The bases – the letters of the genetic alphabet – consist of the four nucleotides mentioned a page or two back: adenine, thymine, guanine and cytosine.

The shape of a DNA molecule, as everyone knows, is rather like a spiral staircase or twisted rope ladder: the famous double helix. The uprights of this structure are made of a type of sugar called deoxyribose and the whole of the helix is a nucleic acid – hence the name ‘deoxyribonucleic acid’. The rungs (or steps) are formed by two bases joining across the space between, and they can combine in only two ways: guanine is always paired with cytosine and thymine always with adenine. The order in which these letters appear as you move up or down the ladder constitutes the DNA code; logging it has been the job of the Human Genome Project.

When it is time to produce a new DNA molecule, the two strands part down the middle, like the zip on a jacket, and each half goes off to form a new partnership. Because each nucleotide along a strand pairs up with a specific other nucleotide, each strand serves as a template for the creation of a new matching strand. If you possessed just one strand of your own DNA, you could easily enough reconstruct the matching side by working out the necessary partnerships:

Most of the time our DNA replicates with dutiful accuracy, but just occasionally – about one time in a million – a letter gets into the wrong place. This is known as a single nucleotide polymorphism, or SNP, familiarly known to biochemists as a ‘Snip’. Generally these Snips are buried in stretches of non-coding DNA and have no detectable consequence for the body. But occasionally they make a difference. They might leave you predisposed to some disease, but equally they might confer some slight advantage – more protective pigmentation, for instance, or increased production of red blood cells for someone living at altitude.

An increase in red blood cells can help a person or group living at high elevations to move and breathe more easily, because more red cells can carry more oxygen. But additional red cells also thicken the blood. Add too many ‘and it’s like pumping oil’, in the words of Temple University anthropologist Charles Weitz. That’s hard on the heart. Thus, those designed to live at high altitude get increased breathing efficiency, but pay for it with higher-risk hearts. By such means does Darwinian natural selection look after us.

The 97

per cent of our DNA commonly called junk is largely made up of clumps of letters that, in Matt Ridley’s words, ‘exist for the pure and simple reason that they are good at getting themselves duplicated31

Even when DNA includes instructions for making genes – when it codes for them, as scientists put it – it is not necessarily with the smooth functioning of the organism in mind. One of the commonest genes we have is for a protein called reverse transcriptase, which has no known beneficial function in human beings at all. The one thing it does do is make it possible for retroviruses, such as HIV, to slip unnoticed into the human system.

All organisms are in some sense slaves to their genes. That’s why salmon and spiders and other types of creature more or less beyond counting are prepared to die in the process of mating. The desire to breed, to disperse one’s genes, is the most powerful impulse in nature.

In one, they took the gene that controlled the development of a mouse’s eye and inserted it into the larva of a fruit fly. The thought was that it might produce something interestingly grotesque. In fact, the mouse-eye gene not only made a viable eye in the fruit fly, it made a fly’s eye. Here were two creatures that hadn’t shared a common ancestor for 500 million years35, yet could swap genetic material as if they were sisters.

In field after field, researchers found that whatever organism they were working on – whether nematode worms or human beings – they were often studying essentially the same genes. Life, it appeared, was drawn up from a single set of blueprints. Further probings revealed the existence of a clutch of master control genes, each directing the development of a section of body, which were dubbed homeotic (from a Greek word meaning ‘similar’) or hox genes38. Hox genes answered the long-bewildering

question of how billions of embryonic cells, all arising from a single fertilized egg and carrying identical DNA, know where to go and what to do – that this one should become a liver cell, this one a stretchy neuron, this one a bubble of blood, this one part of the shimmer on a beating wing. It is the hox genes that instruct them, and they do it for all organisms in much the same way. Interestingly, the amount of genetic material and how it is organized doesn’t necessarily, or even generally, reflect the level of sophistication of the creature that contains it.

Until recently it was thought that humans had at least one hundred thousand genes, possibly a good many more, but that number was drastically reduced by the first results of the Human Genome Project, which suggested a figure more like thirty-five thousand or forty thousand genes – about the same number as are found in grass.

Unfortunately, thirty-five thousand genes functioning independently is not nearly enough to produce the kind of physical complexity that makes a satisfactory human being. Genes clearly, therefore, must co-operate. A few disorders – haemophilia, Parkinson’s disease, Huntington’s disease and cystic fibrosis, for example – are caused by lone dysfunctional genes, but as a rule disruptive genes are weeded out by natural selection long before they can become permanently troublesome to a species or population. For the most part our fate and comfort – and even our eye colour – are determined not by individual genes but by complexes of genes working in alliance.

Even thinking, it turns out, affects the ways genes work. How fast a man’s beard grows, for instance, is partly a function of how much he thinks about sex42 (because thinking about sex produces a testosterone surge). In the early 1990s, scientists made an even more profound discovery when they found they could knock out supposedly vital genes from embryonic mice, and still see the mice often not only

born healthy, but sometimes actually fitter than their brothers and sisters who had not been tampered with. When certain important genes were destroyed, it turned out, others were stepping in to fill the breach.

So now the quest is to crack the human proteome – a concept so novel that the term proteome didn’t even exist a decade ago. The proteome is the library of information that creates proteins. ‘Unfortunately,’ observed Scientific American in the spring of 2002, ‘the proteome is much more complicated than the genome43.

To function, a protein not only must have the necessary chemical components, properly assembled, but then must also be folded into an extremely specific shape. ‘Folding’ is the term that’s used, but it’s a misleading one as it suggests a geometrical tidiness that doesn’t in fact apply. Proteins loop and coil and crinkle into shapes that are at once extravagant

and complex. They are more like furiously mangled coat hangers than folded towels.

a handy archaism) the swingers of the biological world. Depending on mood and metabolic circumstance, they will allow themselves to be phosphorylated, glycosylated, acetylated, ubiquitinated44, farneysylated, sulphated and linked to glycophosphatidylinositol anchors, among rather a lot else. Often it takes relatively little to get them going, it appears. Drink a glass of wine, as Scientific American notes, and you materially alter the number and types of proteins at large in your system45

All the tiny, deft chemical processes that animate cells – the co-operative efforts of nucleotides, the transcription of DNA into RNA – evolved just once and have stayed pretty well fixed ever since across the whole of nature.

Every living thing is an elaboration on a single original plan. As humans we are mere increments – each of us a musty archive of adjustments, adaptations, modifications and providential tinkerings stretching back 3.8 billion years. Remarkably, we are even quite closely related to fruit and vegetables. About half the chemical functions that take place in a banana are fundamentally

the same as the chemical functions that take place in you.

Alexander von Humboldt, yet another friend, may have had Agassiz at least partly in mind when he observed that there are three stages in scientific discovery7: first, people deny that it is true; then they deny that it is important; finally they credit the wrong person.

It is thought that an ice age could start from a single unseasonal summer. The leftover snow reflects heat and exacerbates the chilling effect.

It is mildly disconcerting to reflect that the whole of meaningful human history – the development of farming, the creation of towns, the rise of mathematics and writing and science and all the rest – has taken place within an atypical patch of fair weather. Previous interglacials have lasted as little as eight thousand years. Our own has already passed its ten-thousandth anniversary.

If Earth did freeze over, then there is the very difficult question of how it ever got warm again. An icy planet should reflect so much heat that it would stay frozen for ever. It appears that rescue may have come from our molten interior. Once again we may be indebted to tectonics for allowing us to be here.

If ice sheets advanced again, we have nothing in our armoury that could deflect them. In 1964, at Prince William Sound in Alaska, one of the largest glacial fields in North America was hit by the strongest earthquake ever recorded on the continent. It measured 9.2 on the Richter scale. Along the fault line, the land rose by as much as 6 metres. The quake was so violent, in fact, that it made water slosh out of pools in Texas. And what effect did this unparalleled outburst have on the glaciers of Prince William Sound? None at all. They just soaked it up and kept on moving.

For a long time it was thought that we moved into and out of ice ages gradually, over hundreds or thousands of years, but we now know that that has not been the case. Thanks to ice cores from Greenland we have a detailed record of climate for something over a hundred thousand years, and what is found there is not comforting. It shows that for most of its recent history the Earth

has been nothing like the stable and tranquil place that civilization has known, but rather has lurched violently between periods of warmth and brutal chill.

What is most alarming is that we have no idea – none – what natural phenomena could so swiftly rattle the Earth’s thermometer. As Elizabeth Kolbert, writing in the New Yorker, has observed: ‘No known external force, or even any that has been hypothesized, seems capable of yanking the temperature back and forth as violently, and as often, as these cores have shown to be the case.

It is natural to suppose that global warming would act as a useful counterweight to the Earth’s tendency to plunge back into glacial conditions. However, as Kolbert has pointed out, when you are confronted with a fluctuating and unpredictable climate, ‘the last thing you’d want to do is conduct a vast unsupervised experiment on it28’. It has even been suggested, with more plausibility than would at first seem evident, that an ice age might actually be induced by a rise in temperatures. The idea is that a slight warming would enhance evaporation rates29 and increase cloud cover, leading in the higher latitudes to more persistent accumulations of snow. In fact, global warming could plausibly, if paradoxically, lead to powerful localized cooling in North America and northern Europe.

Take Antarctica. For at least 20 million years after it settled over the South Pole Antarctica remained covered in plants and free of ice. That simply shouldn’t have been possible.

One thought to bear in mind is that if the ice sheets did start to form again, for whatever reason, there is a lot more water for them to draw on this time32. The Great Lakes, Hudson Bay, the countless lakes of Canada – these weren’t there to fuel the last ice age. They were created by it. On the other hand, the next phase of our history could see us melting a lot of ice rather than making it. If all the ice sheets melted, sea levels would rise by 60 metres – the height of a twenty-storey building – and every coastal city in the world would

be inundated.

The extraordinary fact is that we don’t know which is more likely: a future offering us aeons of perishing frigidity or one giving us equal expanses of steamy heat. Only one thing is certain: we live on a knife edge.

To Dubois’ dismay, Schwalbe thereupon produced a monograph10 that received far more sympathetic attention than anything Dubois had written, and followed it with a lecture tour in which he was celebrated nearly as warmly as if he had dug up the skull
NOTE: Sometimes, people–intelligent or stupid–tend to behave in an appallingly irrational way.

For years, the skull – today recognized as one of the supreme

treasures of anthropology – sat as a paperweight on a colleague’s desk14.

For the first 99.99999 per cent of our history as organisms, we were in the same ancestral line as chimpanzees

A human body has 206 bones, but many of these are repeated. If you have the left femur from a specimen, you don’t need the right to know its dimensions. Strip out all the redundant bones and the total you are left with is 120 – what is called a half skeleton.

Homo habilis (‘handy man’) was named by Louis Leakey and colleagues in 1964 and was so called because it was the first hominid to use tools, albeit very simple ones.

‘One of the hardest ideas for humans to accept,’ he says, ‘is that we are not the culmination of anything. There is nothing inevitable about our being here. It is part of our vanity as humans that we tend to think of evolution as a process that, in effect, was programmed to produce us.

According to the Java Man authors, Homo erectus is the dividing line45: everything that came before him was apelike in character; everything that came after him was humanlike. Homo erectus was the first to hunt, the first to use fire, the first to fashion complex tools, the first to leave evidence of campsites, the first to look after the weak and frail.

What is certain is that some time well over a million years ago, some new, comparatively modern, upright beings left Africa and boldly spread out across much of the globe. They possibly did so quite rapidly, increasing their range by as much as 40 kilometres a year on average, all while dealing with mountain ranges, rivers, deserts and other impediments and adapting to differences in climate and food sources.

But it is worth remembering, before we move on, that all of these evolutionary jostlings over five million years, from distant, puzzled australopithecine to fully modern human, produced a creature that is still 98.4 per cent genetically indistinguishable from the modern chimpanzee. There is more difference between a zebra and a horse, or between a dolphin and a porpoise, than there is between you and the furry creatures your distant ancestors left behind when they set out to take over the world.

Sometime about a million and a half years ago, some forgotten genius of the hominid world did an unexpected thing. He (or very possibly she) took one stone and carefully used it to shape another. The result was a simple teardrop-shaped hand-axe, but it was the world’s first piece of advanced technology.

‘Do you know that when nineteenth-century anthropologists first got to Papua New Guinea, they found people in the highlands of the interior, in some of the most inaccessible terrain on earth, growing sweet potatoes. Sweet potatoes are native to South America. So how did they get to Papua New Guinea? We don’t know.

The whole of India has yielded just one ancient human fossil, from

about three hundred thousand years ago. Between Iraq and Vietnam – that’s a distance of some five thousand kilometres – there have been just two: the one in India and a Neandertal in Uzbekistan.’ He grinned.

The traditional theory to explain human movements – and the one still accepted by the majority of people in the field – is that humans dispersed across Eurasia in two waves. The first wave consisted of Homo erectus who left Africa remarkably quickly – almost as soon as they emerged as a species – beginning nearly two million years ago. Over time, as they settled in different regions, these early erects further evolved into distinctive types – into Java Man and Peking Man in Asia, and into Homo heidelbergensis and finally Homo neanderthalensis in Europe. Then, something over a hundred thousand years ago, a smarter, lither species of creature – the ancestors of every one of us alive today – arose on the African plains and began radiating outwards in a second wave. Wherever they went, according to this theory, these new Homo sapiens displaced their duller, less adept predecessors. Quite how they did this has always been a matter of disputation. No signs of slaughter have ever been found, so most authorities believe the newer

hominids simply outcompeted the older ones, though other factors may also have contributed.

Nobody can even quite agree where truly modern humans first appear in the fossil record.

As we have noted elsewhere in the book, modern human beings show remarkably little genetic variability – ‘there’s more diversity in one social group of fifty-five chimps than in the entire human population20,’ as one authority has put it – and this would explain why. Because we are recently descended from a small founding population, there hasn’t been time enough or people enough to provide a source of great variability.

‘Data from any single gene cannot really tell you anything so definitive. If you follow the mitochondrial DNA backwards, it will take you to a certain place – to an Ursula or Tara or whatever. But if you take any other bit of DNA, any gene at all, and trace it back, it will take you someplace else altogether.

Great Rift Valley,

So we are left with the position that for a million years – far,

far longer than our own species has even been in existence, much less engaged in continuous co-operative efforts – early people came in considerable numbers to this particular site to make extravagantly large numbers of tools that appear to have been rather curiously pointless.

We don’t know precisely the circumstances, or even the year, attending the last moments of the last dodo, so we don’t know which arrived first, a world that contained a Principia or

one that had no dodos, but we do know that they happened at more or less the same time. You would be hard pressed, I would submit, to find a better pairing of occurrences to illustrate the divine and felonious nature of the human being – a species of organism that is capable of unravelling the deepest secrets of the heavens while at the same time pounding into extinction, for no purpose at all, a creature that never did us any harm and wasn’t even remotely capable of understanding what we were doing to it as we did it.

According to the University of Chicago palaeontologist David Raup, the background rate of extinction on Earth throughout biological history has been one species lost every four years on average. According to Richard Leakey and Roger Lewin in The Sixth Extinction, human-caused extinction now may be running at as much as 120,000 times that level5.

The result was an extraordinary book called A Gap in Nature, constituting the most complete – and, it must be said, moving – catalogue of animal extinctions from the last three hundred years.

Take the case of the lovely Carolina parakeet. Emerald green, with a golden head, it was arguably the most striking and beautiful bird ever to live in North America – parrots don’t usually venture so far north, as you may have noticed – and at its peak it existed in vast numbers, exceeded only by the passenger pigeon. But the Carolina parakeet was also considered a pest by farmers and easily hunted because it flocked tightly and had a peculiar habit of flying up at the sound of gunfire (as you would expect), but then returning almost at once to check on fallen comrades.

is a truly astounding fact that for a very long time the people who were most intensely interested in the world’s living things were the ones most likely to extinguish it.

Millions of years of isolation had allowed Hawaii10 to evolve 8,800 unique species of animals and plants.

Altogether, during the decade or so of Rothschild’s most intensive collecting, at least nine species of Hawaiian birds vanished, but it may have been more.

In 1890, New York State paid out over one hundred bounties for eastern mountain lions, even though it was clear that the much-harassed creatures were on the brink of extermination. Right up until the 1940s many states continued to pay bounties for almost any kind of predatory creature. West Virginia gave out an annual college scholarship to whoever brought in the greatest number of dead pests –

and ‘pests’ was liberally interpreted to mean almost anything that wasn’t grown on farms or kept as pets.

The impulse to exterminate was by no means exclusively American. In Australia, bounties were paid on the Tasmanian tiger (properly the thylacine), a doglike creature with distinctive ‘tiger’ stripes across its back, until shortly before the last one died, forlorn and nameless, in a private Hobart zoo in 1936.

mention all this to make the point that if you were designing an organism to look after life in our lonely cosmos, to monitor where it is going and keep a record of where it has been, you wouldn’t choose human beings for the job.

A United Nations report of 1995, on the other hand, put the total number of known extinctions in the last four hundred years at slightly under five hundred for animals and slightly over six hundred and fifty for plants – while allowing that this was ‘almost certainly an underestimate14’, particularly with regard to tropical species. A few interpreters think most extinction figures are grossly inflated. The fact is, we don’t know. Don’t have any idea. We don’t know when we started doing many of the things we’ve done.

Behaviourally modern humans have been around for less than 0.01 per cent of Earth’s history – almost nothing, really – but even existing for that little while has required a nearly endless string of good fortune.

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