Life in the distant past spans an immense range of geological time, from early environments to ecosystems much closer to the present. Fossils preserve bodies, tracks, burrows and other traces, while the rocks around them help establish age and setting. These records show that life and environments changed, but preservation is selective: many organisms left no fossils, and some ancient deposits are no longer exposed or have been altered. The guides in this collection connect geological time with the evidence that survives, keeping direct observations distinct from reconstructions of ancient worlds.
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Archean Eon
Explore the Archean Eon from 4,031 to 2,500 million years ago: cratons, oceans, microbial life, stromatolites, komatiites and oxygen oases.
Precambrian
Explore the Precambrian from Earth’s formation to 538.8 million years ago: early crust, life, oxygenation, Snowball Earth and Ediacaran animals.
Ectasian Period
Explore the Ectasian Period from 1,400 to 1,200 million years ago: Nuna rifting, Mackenzie magmatism, changing oxygen and eukaryotes.
Eoarchean Era
Explore the Eoarchean Era from 4,031 to 3,600 million years ago: Acasta gneiss, Isua oceans, early crust and disputed biosignatures.
Phanerozoic Eon
Explore the Phanerozoic Eon from 538.8 million years ago to today: its three eras, twelve periods, changing continents, life and extinctions.
Calymmian Period
Explore the Calymmian Period from 1,600 to 1,400 million years ago: platform covers, rifting Nuna, stromatolites and large eukaryotes.
Hadean Eon
Explore the Hadean Eon from 4,567.30 to 4,031 million years ago: Earth’s accretion, Moon formation, magma oceans, first crust and liquid water.
Mesoarchean Era
Explore the Mesoarchean Era from 3,200 to 2,800 million years ago: ancient rivers, Pongola glaciation, oxygen oases and microbial life.
Neoarchean Era
Explore the Neoarchean Era from 2,800 to 2,500 million years ago: growing cratons, iron-rich seas, microbial life and local oxygen oases.
Orosirian Period
Explore the Orosirian Period from 2,050 to 1,800 million years ago: Nuna, mountain building, Vredefort, Sudbury and microbial seas.
Paleoarchean Era
Explore the Paleoarchean Era from 3,600 to 3,200 million years ago: Pilbara and Barberton crust, stromatolites, komatiites and impact beds.
Proterozoic Eon
Explore the Proterozoic Eon from 2,500 to 538.8 million years ago: oxygenation, supercontinents, Snowball Earth, eukaryotes and early animals.
Rhyacian Period
Explore the Rhyacian Period from 2,300 to 2,050 million years ago: oxygenation, glaciation, Lomagundi, Yarrabubba, Bushveld and Gabon fossils.
Siderian Period
Explore the Siderian Period from 2,500 to 2,300 million years ago: banded iron, the Great Oxidation Event, glaciation and craton rifting.
Statherian Period
Explore the Statherian Period from 1,800 to 1,600 million years ago: stable platforms, Nuna, rifting, layered oceans and early eukaryotes.
Stenian Period
Explore the Stenian Period from 1,200 to 1,000 million years ago: Rodinia, Grenvillian mountains, the Midcontinent Rift and Bangiomorpha.
Ediacaran Period
Explore the Ediacaran Period from about 635 to 538.8 million years ago: soft-bodied communities, first animals, movement traces and skeletons.
Cryogenian Period
Explore the Cryogenian Period from about 720 to 635 million years ago: Sturtian and Marinoan ice ages, Snowball Earth and life beneath ice.
Tonian Period
Explore the Tonian Period from 1,000 to about 720 million years ago: Rodinia rifting, algae, testate amoebae, biominerals and predation.
Why many early mammals were small
Explore the ecological opportunities and limits of small body size in Mesozoic mammals, and what fossils can reveal about their lives.
How Ice Ages changed animals
See how glacial cycles reshaped habitats, opened land bridges and changed animal ranges, adaptations and evolutionary histories.
Why some ancient insects reached giant sizes
Learn what fossils and atmospheric evidence reveal about giant Palaeozoic insects and the limits of the oxygen hypothesis.
Why were ancient oceans full of giants?
Explore why marine ecosystems produced giant reptiles, sharks and invertebrates, and how food webs, buoyancy, climate and extinction shaped their size.
How archaeologists find cities hidden beneath the ground
From tells and satellite images to magnetometry and test trenches, see how archaeologists locate buried settlements and check what instruments can really show.
Mammoth hunting: evidence, risk and resource use
Mammoth bones at a camp do not automatically prove a hunt. Embedded weapons, cut marks, bone patterns and site context help separate hunting from scavenging or natural deaths.
Megalodon
Otodus megalodon was a giant Cenozoic shark known mainly from enormous teeth and rare vertebral sets. Fossils constrain its feeding and growth, while its full body shape and exact maximum size remain model-dependent.
What Earth looked like 300 million years ago
See Earth 300 million years ago, when Pangaea was assembling, coal forests covered humid lowlands and early amniotes lived beside giant arthropods.
When were sharks larger than dinosaurs?
Sharks appeared long before dinosaurs. Meet Carboniferous forms such as Helicoprion and the later giant megalodon, and see what their fossils can tell us.
Giant amphibians of the Carboniferous and Permian
Why some early tetrapods grew large, where the best-known giants lived, and what their fossils can and cannot tell us about swamp ecosystems.
The Paleozoic world before dinosaurs
From Cambrian marine ecosystems to Permian synapsids, explore the Paleozoic world that preceded dinosaurs and the extinction that ended it.
Dinosaurs of Gondwana: changing faunas of the southern continents
Gondwanan dinosaur fossils reveal distinctive southern faunas, continental connections and major gaps in the Cretaceous record.
Mesozoic tectonics: Pangaea broke apart in stages
Pangaea's breakup was a staged process from Triassic rifting to later ocean opening, reshaping coastlines, climates and routes for life.
Why did non-avian dinosaurs not survive the K–Pg extinction?
What impact debris, boundary rocks and fossil patterns reveal about the end-Cretaceous extinction, and why its ecological effects were so severe.
When did dinosaurs live?
Dinosaurs are securely known from about 233 million years ago. Follow their Triassic, Jurassic and Cretaceous history to birds alive today.
Dinosaur diversification in the Cretaceous
Cretaceous dinosaurs diversified into varied regional faunas, but apparent peaks depend on changing fossil sampling and classification.
Animals that lived alongside the first dinosaurs
The first dinosaurs shared Triassic ecosystems with pseudosuchians, synapsids, amphibians, fish and many other animals. Fossils reveal neighbours, not one universal community.
How vertebrates moved onto land
Follow the move of vertebrates onto land through lobe-finned fish, Tiktaalik, early tetrapods, Ichthyostega and the later amniotic egg.
The age of giant trees and insects
Explore Carboniferous coal forests, their giant lycopsids and horsetails, huge griffinflies, Arthropleura, coal formation and eventual decline.
Geological time scale
Explore Earth’s 4.54-billion-year history through eons, eras and periods, with current boundary dates and a clear guide to how the scale is built.
How did life on Earth change through deep time?
A concise timeline of life on Earth, from early microbial traces and oxygenation to animals, life on land, mass extinctions and humans.
Geological time calculator
Enter an age in millions of years to find its geological eon, era, period and selected epoch on the current international time scale.
Mass extinctions
Explore the Big Five mass extinctions, their dates, likely causes, rock-record evidence, survivor patterns and the limits of extinction estimates.
Pangaea: how the supercontinent formed and broke apart
Discover how Pangaea assembled, how its vast interior shaped climate, why the supercontinent broke apart and what evidence supports continental drift.
How palaeontologists study fossils
Follow a fossil from its geological context through excavation, preparation, imaging and comparison, and see what each method can and cannot establish.
How fossils form
How remains become fossils, why soft tissues usually disappear, and how burial, minerals, rock formation and erosion shape the fossil record.
When did the first animals appear on Earth?
What fossils suggest about early animals, the debated Ediacaran biota and the growing diversity recorded in Cambrian rocks.
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Frequently asked questions
What does the fossil record show about life in the distant past?
It documents organisms and traces preserved in rocks, including changes in anatomy, diversity and environments through time. It is incomplete because preservation and later discovery are uneven.
How do researchers place fossils in geological time?
They use stratigraphic relationships, fossil comparisons and radiometric dating where suitable minerals are available. The methods can provide different kinds of age constraints, which are interpreted together.
Can fossils reveal what an ancient environment was like?
Fossils can be compared with sediment, rock structures, plants and other organisms from the same setting. Those clues support environmental reconstructions, but a fossil site is only a partial record of a place and time.
Why are some ancient organisms missing from the fossil record?
Fossilisation requires particular conditions, and remains can be destroyed by erosion, heat or pressure. Animals and plants with delicate bodies or limited geographic ranges are especially unlikely to be represented evenly.