This page lists events in the early prehistory of the universe and the Earth, up to approximately 10,000 BC. Note that many of these dates are speculative or very rough estimates. For events from 10,000 BC onwards, see 10th millennium BC. For greater detail see the articles on the various geological periods.
- 13.7 ± 0.2 billion years ago: beginning of the universe (the Big Bang)
- 13.2 billion years ago: existence of the first known star-forming galaxies
- 4.6 billion years ago: the solar system begins to form
- 4.5 billion years ago: formation of the Earth (see Age of the Earth)
- 3.9 to 4.1 billion years ago: origin of life (cyanobacteria)
- 2.3 billion years ago: first known Snowball Earth ice age
- 1.8 to 2.1 billion years ago: appearance of the earliest Eukaryotes
- 750 million years ago: beginning of a possible Snowball Earth ice age
- 600 million years ago: first complex multicelled lifeforms
- 580 million years ago: end of possible Snowball Earth ice age
- 575 million years ago: origin of the oldest animal fossils
- 540 million years ago: end of the Precambrian period and beginning of the Cambrian. Time of the Cambrian explosion and appearance of the first Vertebrates.
- 500 million years ago: Ordovician period begins
- 435 million years ago: Silurian period begins
- 420 million years ago: first creatures with lungs
- 400 million years ago: Devonian period begins
- 340 million years ago: Carboniferous period begins
- 280 million years ago: Permian period begins
- 251.4 million years ago: the Permian mass extinction; Palaeozoic era ends. Beginning of the Triassic period, the Mesozoic era and of the age of the dinosaurs.
- 195 million years ago: Jurassic period begins; appearance of the earliest mammals
- 135 million years ago: Cretaceous period begins
- 65 million years ago: Cretaceous-Tertiary extinction event at the end of the Cretaceous period (end of the Mesozoic era); start of the Tertiary period (Cenozoic era). End of the age of the dinosaurs.
- 60 million years ago: the first primates begin to evolve
- 49 million years ago: whales return to the water
- 40 million years ago: age of the Catarrhini parvorder; first canines evolve
- 36 million years ago: end of Eocene, start of Oligocene epoch
- 34 million years ago: cats begin to evolve
- 26 million years ago: emergence of the first true elephants
- 24 million years ago: Miocene epoch begins
- 20 million years ago: first forms of grass appear
- 18-12 million years ago: emergence of the Hominidae family
- 5-7 million years ago: Pan/Homo split
- 5.5 million years ago: appearance of the genus Ardipithecus
- 5 million years ago: Pliocene epoch begins
- 4.5 million years ago: appearance of the genus Australopithecus
- 4 million years ago: start of last ice age
- 2.5 million years ago: emergence of the genus Homo
- 1.5 million years ago: Pleistocene epoch (Quaternary period) begins; earliest possible evidence of the controlled use of fire by Homo erectus
- 790,000 years ago: earliest demonstrable evidence of the controlled use of fire by Homo erectus
- 700,000 years ago: last reversal of the earth's magnetic field
- 500,000 years ago: colonisation of Eurasia by Homo erectus
- 300,000 years ago: Homo sapiens separated from Homo erectus (Middle Paleolithic)
- 250,000 years ago: appearance of Homo neanderthalensis
- 200,000 years ago: appearance of Homo sapiens
- 160,000 years ago: split between Homo sapiens idaltu and Homo sapiens sapiens
- 150,000 years ago: time of mitochondrial Eve
- 125,000 years ago: peak of the Eemian interglacial period
- 100,000 years ago: earliest estimate for the domestication of dogs
- 90,000 years ago: time of Y-chromosomal Adam
- 75,000 years ago: ancestors of the Indigenous Australians reached Australia
- 70,000 years ago: possible Toba catastrophic event
- 60,000 years ago: out of Africa migration
- 40,000 years ago: Cro-Magnon colonisation of Europe (Upper Paleolithic)
- 29,000 years ago (27,000 BC): extinction of Homo neanderthalensis.
- 23,000 BC: first colonisation of North America
- 19,000 BC: Last Glacial Maximum
- 18,000 BC: the oldest known tally stick (the Ishango Bone)
- 10,000 BC: land ice leaves Denmark and southern Sweden; start of the Holocene epoch and Neolithic Age and end of the last Ice Age.
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