| ERA | PERIOD | EPOCH | BEGINNING | MAJOR EVENTS | |
|---|---|---|---|---|---|
|
Cenozoic (age of mammals) |
Quaternary | Holocene | 10,000 | present climate; modern mammals |
|
| Pleistocene | 1,640,000 | recent ice ages; various human species |
|||
| Tertiary | Pliocene | 5,200,000 | near-human species and other near-modern mammals |
||
| Miocene | 23,300,000 | apes flourish; savanna grazing animals evolve |
|||
| Oligocene | 35,400,000 | monkeys, apes, and other mammal families evolve |
|||
| Eocene | 56,500,000 | prosimians flourish; possible early monkeys |
|||
| Paleocene | * 65,000,000 | earliest primates (proto- prosimians) |
|||
|
Mesozoic (age of reptiles) |
Cretaceous | 146,000,000 | archaic mammals and birds begin to replace dinosaurs; flowering plants |
||
| Jurassic | 208,000,000 | dinosaurs dominant; primitive mammals spread; toothed birds |
|||
| Triassic | * 245,000,000 | first dinosaurs and first egg-laying mammals |
|||
|
Paleozoic (ancient life forms) |
Permian |
 |
290,000,000 | spread of reptiles and insects; first mammal-like reptiles |
|
| Carboniferous | * 363,000,000 | amphibians dominant; forests flourish; reptiles and modern insects appear |
|||
| Devonian | 409,000,000 | fish dominant; amphibians appear; first forests |
|||
| Silurian | * 439,000,000 | first land plants; fish with jaws; air breathing animals |
|||
| Ordovician | * 510,000,000 | invertebrates dominant; first vertebrates (jawless fish) |
|||
| Cambrian | * 570,000,000 | invertebrates dominant (worms, jellyfish, trilobites, etc.) |
|||
| P r e C a m b r i a n |
Proterozoic (earliest life forms) |
|
|
3,000,000,000 | protozoa, sponges, and algae |
| 3,500,000,000 | first
clear evidence of life (one celled bacteria) |
||||
| Azoic (no life forms) |
|
|
4,550,000,000 | origin of the earth | |