The Evolutionary Timeline
| Life Forms |
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 |
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.
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