The eight eras of the timeline

The last five centuries: the period in which the world became connected, then industrial, then digital. Printing spreads ideas faster than handwriting can; empires and revolutions redraw the map; steam, electricity and engines change how people work; two world wars and a cold war reshape the century; then screens, the internet and the smartphone compress everything again. Most of the moments you know best live here, which makes this era a trap: it is easy to be twenty years out and feel certain.

In the game: the Modern Era is the narrow, crowded end of the timeline. Technology words are the best clue: “broadcast”, “computer”, “smartphone”. If a statement mentions anything digital, you are almost certainly in the last few decades.

The thousand years or so between the end of the Western Roman Empire and the Renaissance: castles and cathedrals, monasteries and universities, trade caravans and pilgrimage routes, plagues and dynasties. It is not a single “dark age” — the period includes the Islamic Golden Age, Song-dynasty printing, Gothic architecture and the first universities.

In the game: watch for castles, cathedrals, crusades, monks, knights and parchment. Names of polities help — a “kingdom” or “caliphate” usually points here rather than to the modern state system.

The first cities and the invention of writing: Mesopotamia, Egypt, the Indus valley, Shang China, Persia, Greece, Rome and the empires of Mesoamerica. Writing appears around five thousand years ago, and with it the historical record begins — kings, taxes, laws, epic poems, and the first calendars. It is an era of firsts: law codes, coinage, libraries, the olympics.

In the game: look for ziggurats, pharaohs, city-states, bronze, amphorae, legions and cuneiform. “First” moments about laws, money, cities and written records cluster here. Remember that the era ends at the fall of the Western Roman Empire in 476 CE, which is a useful right-hand fence.

The long stretch in which humans — and before us, other hominins — lived as hunter-gatherers. Fire, knapped stone tools, cave painting, the first jewellery and the first burials all belong here, and so does the great migration out of Africa. Near the end of the era comes one of the biggest changes in human history: farming. Agriculture appears around 12,000 years ago in several places independently, and the first villages follow.

In the game: the Stone Age is the first band where the timeline starts to compress dramatically. A bracket here can sensibly cover tens of thousands of years. Watch for cave art, mammoth bones, flint, and the first crops or pottery — those last two sit near the boundary with the Ancient World.

The game's biggest shorthand. This band covers the long age of mammals after the non-avian dinosaurs disappeared: the rise of grasslands, the evolution of whales, horses, primates and early hominins. It includes the Pleistocene ice ages that gave the era its name — the great ice sheets and the mammoths — but it also includes the much warmer epochs before them. In textbook terms this spans most of the Cenozoic.

In the game: think in millions of years, not thousands. If a moment involves a woolly mammoth, a sabre-toothed cat or an early human ancestor, it is here. If it involves the first primates or the spread of grasslands, it is here too — both are much older than the Ice Age's popular image.

The great age of animals. It opens with the Cambrian explosion around 541 million years ago, when complex animal life radiated in the oceans; continues through fish, the first land plants, insects, amphibians and the Permian extinction, the largest mass extinction we know of; then enters the Mesozoic, when dinosaurs dominated the land and the first birds evolved from them. It ends with the asteroid impact 66 million years ago, which wiped out the non-avian dinosaurs.

In the game: even though the band is called Dinosaurs, it starts hundreds of millions of years before the first dinosaur. Look for trilobites, coal forests, amphibians, and the first birds alongside T. rex. If a moment says “first”, ask whether it means “first animal” (early in this band) or “first dinosaur” (middle of it).

A molten planet cools, oceans form, and life switches on. This band covers the Hadean — Earth's formation and the giant impact that created the Moon — then the Archean, when the first single-celled life appears, and the Proterozoic, when oxygen fills the atmosphere, complex cells evolve and the planet goes through enormous ice ages. It is more than four billion years of Earth's history,

In the game: this is a band where being wrong by a hundred million years is not really wrong. Watch for geology and atmosphere: continents forming, oxygen, ice ages, the first cells. If a moment is about rocks or oceans rather than creatures, it belongs here.

The opening act of everything. The Big Bang itself, then the first stars, the first galaxies, the formation of the Milky Way and the heavy elements that later made planets and people possible. This band takes up roughly the first nine billion years of the universe — most of the timeline —

In the game: think in billions. A sensible range can cover hundreds of millions or even a couple of billion years. Watch for stars, galaxies, nebulae and the formation of the solar system, which sits at the boundary with the next band.