Timeline Information

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Biological Events Timeline: (MY = Million years before present)

• First bacteria - 3500 MY
• Early eukaryotes - 1900-1700 MY
• Trace animal fossils - 1000 MY
• Abundant soft-bodied animals - 700 MY
• First fish - 505 MY
• Early land plants - 438 MY
• First amphibians - 370 MY
• First reptiles - 310 MY
• End Permian mass extinction event (destroyed 82% of all genera) - 245 MY
• Dinosaurs appear - 240 MY
• First mammals - 225 MY
• First birds - 200 MY
• Flowering plants appear - 140 MY
• End Cretaceous mass extinction event (including last dinosaurs); age of mammals begins - 66 to 65 MY
• Early horses adn other familiar animals - 37 MY
• Earliest humans - 2 MY
• Humans dominant - 0 MY (now)

Geological Events Timeline:

• Formation of Earth - 4600 MY
• Oldest rocks yet discovered - 3950 MY
• Significant oxygen in atmosphere - 1500 MY
• Start of formation of Appalachian Mountains - 450 MY
• Start of supercontinent Pangaea (all continents pushed together) - 360 MY
• Abundant coal-forming swamps - 320 MY
• Break-up of Pangaea begins 225 MY
• Massive volcanic activity marking opening of north Atlantic Ocean - 60 MY
• Formation of Rocky Mountains - 60 MY
• Major deformation of Alps and Himalayas - 50 MY
• Ice Age which covered much of Ohio - 1.6 MY to 10,000 years
• Hawaii (big island) eruptions start - 0.7 MY
• Eruption of Mount St. Helens - 0 MY (May 1980)

Geological Eras Information:

• Archaean Era 3600-4600 MY(origin of life, beginning of photosynthesis, increaed abundance of oxygen in atmosphere, diversification of prokaryotes)
• Proterozoic Era 2500-3600 MY(earliest eukaryotes, trace animal fossils, first multicellular fossils)
• Paleozoic Era 290-2500 MY
  • Cambrian Period 543-2500 MY(marine animals diversify, diverse algae)
  • Ordovician Period 500-543 MY(diversification of invertebrates, mass extinction at the end of this period)
  • Sulurian Period 439-500 MY(earliest terrestrial vascular plants)
  • Devonian Period 409-439 MY(diversification of boney fishes, mass extinction at the end of this period)
  • Carboniferous Period 354-409 MY(Gondwanaland and small northern continents form, early winged insects, first reptiles)
  • Permian Period 290-354 MY(Pangaea, glaciations, major mass extinction of marine life at end of this period)
• Mesozoic Era 144-290 MY
  • Triassic Period 251-290 MY(continents begin to separate, first dinosaurs, first mammals)
  • Jurassic Period 206-251 MY(first birds, gymnosperms dominate, evolution of angiosperms)
  • Cretaceous Period 144-206 MY(most continents separated, mass extinction at end of period including dinosaurs)
• Cenozoic Era 0.01-144 MY
  • Tertiary Period 5.2-144 MY (continentss near modern positions, climate cools, radiation of mammals, birds, snakes, pollinating insects, angiosperms)
    • Paleocene Epoch 65-144 MY
    • Eocene Epoch 55.6-65 MY
    • Oligocene Epoch 33.5-55.6 MY
    • Miocene Epoch 23.8-33.5 MY
    • Pliocene Epoch 5.2-23.8 MY
  • Quaternary Period 0.01-5.2 MY (continents in modern positions, repeated glaciations, lowering of sea level, extinctions of large mammals, evolution of Homo erectus and Homo sapiens, rise of agriculture)
    • Pleistocene Epoch 1.8-5.2 MY
    • Recent (Holocene) Epoch 0.01-1.8 MY

Other Information on the Age and History of the Earth is Available at:

• The Age of the Earth - a page that discusses evidence dating the earth, it is a highly scientific analysis but good background for advanced classes
• The Geologic Time Scale - a page explaining divisions in the geologic time scale and the principles and theories on which the time scale is based

This information was adapted from a compilation of resources including Evoluationary Biology by Douglas J. Futuyma, Sunderland, MA: Sinauer Associates, Inc. 1998.

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