Different fossils were laid down at different points in the geological timescale:

• Precambrian (3.8 billion to 570 million years ago)
  • Bacteria and blue-green algae
• Cambrian (570 to 500 million years ago)
  • First invertebrates
• Ordovician (500 to 440 million years ago)
• Silurian (440 to 410 million years ago)
  • First land plants
  • First land invertebrates
• Devonian (410 to 365 million years ago)
  • First ferns and seed plants
  • First insects
  • First amphibians
• Carboniferous (365 to 290 million years ago)
  • First flying insects
  • First reptiles
• Permian (290 to 245 million years ago)
  • Extinction of trilobites
• Triassic (245 to 210 million years ago)
  • First dinosaurs
  • First mammals
• Jurassic (210 to 140 million years ago)
  • First birds
• Cretaceous (140 to 65 million years ago)
  • First flowering plants
  • First primates
  • Extinction of dinosaurs
  • Extinction of ammonites
• Paleocene (65 to 55 million years ago)
  • Diversification and spreading of mammals
• Eocene (55 to 38 million years ago)
• Oligocene (38 to 25 million years ago)
  • First grass
• Miocene (25 to 5 million years ago)
• Pliocene (5 to 2 million years ago)
  • First hominids