16.5 — The Connected Dots

A supernova exploded somewhere in this arm of the galaxy about 4.6 billion years ago, and its shock wave compressed a cold cloud of gas and dust past the point where gravity took over.

Follow the thread from there to the phone in your hand, without a break.

The thread

The cloud collapsed and flattened into a disc, because any rotation speeds up as a cloud shrinks (Chapter 1.2). The centre ignited into the Sun. Dust stuck to dust, pebbles swarmed and collapsed into rocks, rocks grew into planets.

Inside the frost line, only metal and silicate could survive as solids, so the inner planets were small and rocky. Earth was one of the leftovers.

A body the size of Mars struck it a glancing blow, and the debris became the Moon — which gave the planet a stable tilt, a slowing spin, and tides.

The planet melted and separated: iron core, rock mantle, thin crust (Chapter 1.3). The liquid iron core convects and generates the magnetic field that keeps the solar wind from stripping the atmosphere away, which is what appears to have happened to Mars.

Heat still leaking out of that interior moves the plates (Chapter 1.5). Plates carrying continents collide, and where India met Asia the crust doubled in thickness and rose (Chapter 1.8).

That wall of mountains, with a plateau behind it heating the air five kilometres up, created the monsoon (Chapter 2.5) — and the rivers running off it ground the mountains into the most fertile large plain on Earth.

Life appeared early and was single-celled for two billion years (Chapter 3.1). One cell swallowed another and kept it, which is why your cells have mitochondria. Photosynthesis released oxygen, which poisoned most of what was alive, rusted the iron out of the oceans into the ore that the steel age would later mine (Chapter 1.12), and built the ozone layer that made dry land survivable.

Five times, most of it was destroyed. The last time, an asteroid struck a shallow sulphur-rich shelf at Chicxulub, blocked the sunlight, and ended the dinosaurs (Chapter 1.10). The small nocturnal mammals that survived had the world to themselves.

The climate cooled as the Himalaya rose and weathered. Forests shrank, grasslands spread, and an African ape stood up to cross them (Chapter 3.2). It walked before it thought — the brain came three million years later, paid for by meat, marrow and fire (Chapter 3.4).

It made tools, wore clothes, spoke, painted, and walked to every continent (Chapter 3.5, 3.6).

Then the ice retreated and the climate steadied, and within a few thousand years people in eleven separate places began planting seeds (Chapter 3.7). It made them shorter and sicker and it fed more of them, so there was no way back.

Surplus grain could be stored, counted and taken. So there were priests, soldiers, kings, taxes and writing — which began as a receipt (Chapter 3.11, 4.1).

Bronze required tin from one place and copper from another, which made the first international system, and when a drought hit it, it collapsed everywhere at once (Chapter 4.6). Iron ore was everywhere, so iron armed everybody, cleared the Gangetic forests, and fed the kingdoms in which the Buddha argued (Chapter 3.12, 6.3).

Empires learned that terror is cheap and brittle and co-option is expensive and durable (Chapter 4.7). Rome turned defeated enemies into citizens and conquered the Mediterranean, and destroyed its own republic doing it (Chapter 5.3).

Ships followed the monsoon between India and the Mediterranean, carrying pepper west and silver east, and Buddhism and the plague along the same roads (Chapter 5.7).

Arabic scholars preserved Greek learning, corrected it, invented algebra and the hospital, and passed it to a Europe that would later claim it had leapt over the gap (Chapter 7.2, 8.1).

The Mongols connected the continent and the connection carried the Black Death, which killed a third of Europe and, by making labour scarce, broke serfdom in its western half and raised wages (Chapter 7.6, 7.7).

High wages and cheap coal made machines worth building in Britain and nowhere else (Chapter 9.5). A goldsmith's press, a metal alloy and an oily ink had already made knowledge cumulative (Chapter 8.2). Gunpowder made war expensive enough to force the invention of the tax state and the national debt (Chapter 8.3, 9.2).

Ships with gunports crossed oceans. Microbes that ten thousand years of living beside cattle had prepared Europeans for, and had not prepared Americans for, emptied two continents (Chapter 8.5). Sugar needed labour that killed the workforce, so 12.5 million people were shipped across the Atlantic and the traders kept the accounts (Chapter 8.6).

Coal from the Carboniferous — laid down when trees evolved lignin before the fungi that rot it caught up — went into the machines (Chapter 1.10, 9.5). Output per person began rising and has not stopped.

A trading company took a subcontinent by making credible offers to people whose loyalty was for sale in a political system that had no way to coordinate against it (Chapter 6.15, 6.16).

Two world wars, a depression between them, and a hundred and fifty million dead by political violence (Chapter 11.12). And in the same century child mortality fell from a third to under four percent, and life expectancy doubled.

The empires ended within a generation (Chapter 10.9). India kept the elections, the courts and the army in barracks, and chose an economic model that cost it forty years (Chapter 6.24, 6.28).

And the carbon that the slow cycle took tens of millions of years to bury has been returned to the air in about two hundred (Chapter 14.1) — which is now warming the planet whose orbital wobbles produced the ice ages that made the climate stable enough for any of this.

And the phone in your hand contains silicon from sand, lithium from a dry basin in the Andes, cobalt from Congo, and rare earths processed in China (Chapter 12.10) — all of it concentrated by the geology of Chapter 1.12, assembled by supply chains that exist because of a steel box (Chapter 12.8), and running on mathematics that came from India through Baghdad (Chapter 3.11).

Every link in that chain is in this volume, and there is no break in it.

What the thread shows

Four things, and they are the volume's conclusions.

Almost nothing was inevitable. The asteroid's arrival time. The Great Khan's death that turned the Mongols back. The wrong turn in Sarajevo. Arkhipov saying no. **Rerun the tape and you get a different world, and the accounts that read history as destiny — national, racial, religious or economic — are wrong about the mechanism.

And almost nothing was arbitrary either. The deserts are at 30 degrees because the Earth is a sphere that spins. Empires collapsed for reasons. India lost battles for institutional reasons that can be named. The mechanisms are real, and they operate in a system with enormous variance, which is why history is neither random nor determined.

The differences between societies are institutional rather than innate. This is the finding this volume commits to most firmly, because it comes from several directions independently — the two Nogales, the two Koreas, the same Indians earning multiples abroad, the same Chinese population under Mao and after Deng (Chapter 9.4, 16.3).

And what has actually improved was built, defended and can be lost. The eight-hour day, the vote, the abolition of slavery, the courts, the vaccines, the peace between great powers. None of it arrived automatically. Chapter 15.4's list was legislated after organisation, against opposition. Chapter 12.2's nuclear taboo has held for eighty years and is maintained by arrangements that are currently lapsing.

What it is for

This volume was written for a reader who wanted to know the world for its own sake, and it should end by saying what that is worth.

Three things.

It makes the news intelligible. A dispute over a sea, a currency movement, an aftershock, a border, an inflation figure, a famine, a strike — each of them now has a mechanism behind it that you can name. You are not dependent on anyone's summary.

It calibrates you. Chapter 16.4's whole argument. The habit of asking who produced this evidence, what would change my mind, and whether my confidence exceeds what I actually know is the single most useful thing in these sixteen Parts, and it applies to your work and your relationships as much as to politics.

And it changes the scale you think on. Chapter 1.1's calendar: the Earth's history as one year, and everything in Parts 4 to 15 in the last thirty seconds. That is not a way of making human life feel small. It is a way of noticing how recent and how fragile everything you take for granted is, and therefore how much of it depends on being maintained.

The last thing

The people in this volume who changed the most were not, in the main, the powerful ones.

A clerk in Liverpool noticed that ships went to the Congo with guns and came back with rubber, and worked out that nothing was being bought (Chapter 11.1).

A Danish seismologist working alone with data in oatmeal boxes found the Earth's inner core (Chapter 1.3).

A Soviet officer decided a warning of five incoming missiles was a false alarm because a real attack would involve hundreds (Chapter 12.2).

A ten-year-old on a beach in Thailand recognised what a receding sea meant, because she had learned it in a geography lesson two weeks earlier (Chapter 1.6).

A group of librarians in Timbuktu moved several hundred thousand manuscripts out of a city in rice sacks (Chapter 7.8).

And Berkeley Earth's physicist, funded by people who expected him to debunk the temperature record, rebuilt it from scratch, found it was right, and said so publicly (Chapter 14.2).

None of them held office. Each of them knew something specific, and acted on it when it counted.

That is what this volume is for.

Where to go next

Volume VI is the mind — psychology, learning, emotion and communication — which is the machinery this volume kept referring to and never explained.

Volume VII is philosophy and the traditions of meaning, which takes the questions Chapter 4.8 raised and gives them the serious treatment a history could not.

Volume IX is survival: what to do in the sixty seconds when the geology, the weather or the medicine in this book stops being interesting and starts being urgent.

And Volume V is your own body, which is the one piece of the physical world you are responsible for.

Read them in any order. The thread runs through all of them, and you have the whole of it now.