Natural History Museum

Life Through Time Exhibit

Richard Paselk*


The development of life over the last 3,700 million years of the Earth's history is one of the great stories told by modern science. During most of this time living things left only traces to indicate their existence. Then, about 544 million years ago, during what is referred to as the Cambrian explosion, animals learned how to make hard, mineralized body parts. Suddenly rocks resulting from sand and mud deposits become laden with fossil remains, and our picture of ancient life grows enormously in scope and detail.



4,570 to 542.0 Million years ago
The Precambrian encompasses nearly 90% of Earth's history, and almost a third of the history of the Universe. It begins with the formation of the Earth from the dust and gas of the solar nebula, includes the origin and early evolution of life, the beginning of plate tectonics, and the development of an oxygen atmosphere. It ends with one of Earth's great extinction events, making way for the development of modern plants and animals. Case #1. View case index

PHANEROZOIC EON (542.0 Million years ago to present):

Paleozoic Era (542.0 to 251.0 Million years ago) 

Cambrian Period

542.0 to 488.3 Million years ago
Sudden appearance of fossil remains referred to as the Cambrian explosion. Marine animals with skeletons make their first appearance in shallow seas. The domination of trilobites is reflected by the large number in our exhibit, which also includes early brachiopods and burrows. Case #2. View case index

Ordovician Period

488.3 to 443.7 Million years ago
More complex shelled animals lived in seas during this period, which ended in a mass extinction. Case #3. View case index

Silurian Period

443.7 to 416.0 Million years ago
A warm climate and high sea level gave rise to large reefs, while on land simple land plants emerged. Case #4. View case index 

Devonian Period

416.0 to 359.2 Million years ago
New predators such as sharks, bony fishes and ammonoids ruled the oceans. On land, scorpions, spiders, wingless insects and the first amphibians were starting to thrive. Case #5. View case index 

Carboniferous Period

359.2 to 299.0 Million years ago

Mississippian Subperiod

359.2 to 318.1 Million years ago
During this period, sea lilies dominated the limestone seas and reptiles began to appear along with ferns. Case #6. View case index

Pennsylvanian Subperiod

318.1 to 299.0 Million years ago
Coal swamp forests thrived during this period. A dragonfly ancestor lived then with a 29-inch wing inch. Case #7. View case index

Permian Period

299.0 to 251.0 Million years ago
Reptiles started to thrive in water and on land and conifer forests appear in this period. The Permian ended with greatest mass extinction event known in Earth's history. Case #8. View case index 

Mesozoic Era (251.0 to 65.5 Million years ago)

Triassic Period

251.0 to 199.6 Million years ago
The Permian extinction event was so severe that entirely new fauna and flora appear in the Triassic. Mammals and dinosaurs started to appear in this period. Case #9. View case index 

Jurassic Period

199.6 to 145.5 Million years ago
Ammonites and dinosaurs made a huge comeback after near extinction at the end of the Triassic. The first bird fossils and flying pterosaurs showed up in the fossil record. Case #10. View case index 

Cretaceous Period

145.5 to 65.5 Million years ago
The first flowering plants appeared at the end of the Mesozoic era, along with the extinction of dinosaurs, pterosaurs, mesosaurs and ammonoids, to name a few. Case #11. View case index 

Cenozoic Era (65.5 Million years ago to present)

Paleogene Period

65.5 to 23.03 Million years ago
Primitive mammals and birds began to flourish. The Paleogene includes what used to be the first part of the Tertiary. The Paleogene has three divisions:

  • Paleocene Epoch (65.5 to 55.8 Million years ago).
  • Eocene Epoch (55.8 to 33.9 Million years ago)
  • Oligocene Epoch (33.9 to 23.03 Million years ago).

Case #12. View case index 

Neogene Period

23.03 Million years ago to present
Mammals evolved in oceans and on land. The Neogene now includes Geologic time up to the present, covering what used to be the later Tertiary and the Quaternary. The Neogene has four divisions:

  • Miocene Epoch (23.03 to 5.332 Million years ago)
  • Pliocene epoch (5.332 to 1.806 Million years ago)
  • Pleistocene Epoch (1.806 to 0.0115 Million years ago)
  • Holocene Epoch (11.5 thousand years ago to the present). The Holocene may actually simply be the latest interglacial of the Pleistocene.

Case #13. View case index

Prehistoric Mammals of the Cenozoic

65.5 Million years ago to present
Six cases highlight major mammal groups found in North America over the entire Cenozoic.

Other Ways to Navigate the Life Through Time Exhibit

1. You can also explore the Museum's Life Through Time Mural. The organisms on this mural are linked to images of fossils of these organisms. The time line at the bottom of the mural will lead to illustrated essays for each geological period.

2. View an interactive Geological Timeline that serves as a key to the Life Through Time cases in the museum.

Life Through Time Mural icon
Life Through Time Mural
Geological Timeline icon
Geological Timeline

*The Life Through Time exhibit web pages were researched, written and designed by Richard Paselk, associate curator.

Last modified 4 October 2012