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| Timeline: Universal Origins |
How did the Earth -- and everything on it -- come into existence? This timeline shows the progression from empty space to life as we know it.
Earth formed 4.6 billion years ago.
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4.6 billion years ago
Solar system and Earth formed. Radioactive and gravitational heating leads to multi-layered structure and outgassing of methane, ammonia, hydrogen, nitrogen, and carbon dioxide.
3.8 billion years ago
Earth's crust solidifies. Oldest rocks found on Earth today are formed. Water is condensed into oceans.
3.5 to 2.8 billion years ago
First signs of life -- prokaryotic cells -- develop. Simple blue-green algae begins photosynthesis, releasing oxygen into atmosphere.
1500 to 600 million years ago
Multicellular organisms arise. First animals with shells and skeletons arise, all marine. Trilobites dominant.
500 to 450 million years ago
First fish arise.
420 million years ago
Millipedes, the first land animals, evolve.
375 million years ago
Appalachian mountains are formed when North American, African, and European plates collide. Primitive sharks appear.
350 to 300 million years ago
Amphibians, primitive insects, primitive ferns evolve.
300 to 200 million years ago
Climate is warming. Continental plates begin to break into continents. Reptiles, winged insects, roaches, termites, bees, primitive crocodiles, and mammals evolve. First dinosaurs.
200 to 20 million years ago
Climate warmer than present. Kangaroos, cranes, modern sharks, herons, storks, koalas evolve. Dinosaurs disappear and mammals begin their reign. Flowering plants and modern trees emerge. Volcanism forms Rocky Mountains. Arabia and Africa split at Red Sea Rift. California collides with mid-Pacific ridge. Forests reduced, grassy plains increase.
20 to 2 million years ago
Chimpanzees and earliest humans evolve. Stone tools used. Volcanism forms isthmus between North and South America.
2 to .1 million years ago
Most recent ice age.
1.6 to .2 million years ago
Homo erectus exists, tames fire. Mastodons, mammoths become extinct.
.5 to 0 million years ago
Rise of Homo sapiens -- modern humans.
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