The Evolutionary Timeline

Life Forms1 Millions of Years Ago Period Era
Humans 0 Quaternary Cenozoic
Mammals arrive 50 Tertiary
Dinosaurs flourish, Tyrannosaurus rex, Triceratops, etc 100 Cretaceous Mesozoic
Reptiles, pre-bird, archaeopteryx 150-175 Jurassic
Proliferation of land plant life 200 Triassic
Reptile branches, pre-mammalian forms. Dinosaurs arrive. 250 Permian Paleozoic
Amphibians and first reptiles on land 300 Carboniferous
plants from the sea began to colonize the land. 350 Devonian
Vertebrate fish, jawless, 425 Silurian
Marine Invertebrates, trilobites, cephalopods... 450-500 Ordovician
Trilobites, snails, brachipods 500-575 Cambrian
Multicellular life forms. Soft-bodied animals, worms, jellyfish, etc. 600-650 Algonkian PreCambrian
Life begins 3.5 billion years ago
  • 1. This chart was adapted from an insert called the "Tower of Time" by John Gurche as reproduced in The Thread of Life: The Smithsonian Looks at Evolution, by Roger Lewin, Smithsonian Books, Washington, D.C., Distributed by W.W. Norton & Company, New York, N.Y. 1982.