Genes.media Deep Time

The history of Earth

Four thousand five hundred and forty million years are not told in two hundred steps: they are walked. This page keeps the milestones — the ones the corpus rates the spine of the story, or a first-order landmark: sixty-five out of two hundred — grouped by era, oldest first. The choice was not made while writing this page. It was made entry by entry, at review, and it already decides what the timeline shows when space runs short. What is left out is not left out for counting less, but because the story holds without it. The full list of two hundred is in the contents.

65 milestones out of 200, in 10 chapters

Hadean4.54 Ga → 4.03 Ga

Five hundred million years without a single rock left to show for them. The eon takes its name from the underworld, and it is the only division of Earth's history defined by the absence of what should record it.

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Eoarchean4.03 Ga → 3.6 Ga

The dawn era, and the first four hundred million years for which any rock survives at all. What it holds is thin, contested, and among the most important evidence there is.

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Paleoarchean3.6 Ga → 3.2 Ga

Four hundred million years in which life stops being a contested trace and becomes a structure you can walk up to and touch.

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Mesoarchean3.2 Ga → 2.8 Ga

Somewhere in this era the crust may start behaving as it does today, one plate sliding beneath another and driving the machinery that builds continents.

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Paleoproterozoic2.5 Ga → 1.6 Ga

Nine hundred million years, and the most violent change the planet has undergone: the air fills with oxygen, and almost everything alive is poisoned by it.

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Mesoproterozoic1.6 Ga → 1 Ga

Six hundred million years in which, as far as anyone can tell, remarkably little happens. They sit at the heart of what the literature calls the boring billion, and the nickname is a confession.

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Neoproterozoic1 Ga → 539 Ma

Four hundred and sixty million years in which ice reaches the tropics more than once, a supercontinent breaks apart, and the first animals appear.

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Paleozoic539 Ma → 252 Ma

Two hundred and eighty-seven million years, from the first shelled animals to the worst extinction in the record. Life leaves the water in this era and never fully returns.

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Mesozoic252 Ma → 66 Ma

A hundred and eighty-six million years between two catastrophes: the only era on the chart that both begins and ends with a mass extinction.

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Cenozoic66 Ma → 2026

The last sixty-six million years, in which mammals inherit a world emptied by an asteroid, grasslands spread, ice returns, and one primate lineage ends up drawing timelines.

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