| GEOLOGIC TIME This infographic depicts the history of the Earth and the life that devel-
oped upon it. The Earth has been around for nearly 4.6 billion years and
much has happened in that immense span of time, from global glaciations
to massive asteroid impacts. Scientists have learned about the long, com-
plex history of the planet by studying layers of rock in the Earth’s crust.
These layers contain fossils of plants and animals that lived on Earth, only a
tiny fraction of which still exist today. By examining the composition of
rocks and the types of fossils in them, scientists have created a timeline of
Earth’s history. It is broken up into sections based on major events, like
global climate changes and mass extinctions. Use this infographic to
explore the evolution of Earth and the life upon it.
ARCHEAN PROTEROZOIC MESOZOIC CENOZOIC
4.6 billion years ago: Earth is formed. The moon forms about 100 million years afterwards.
3.5 billion years ago: First evidence of single-celled organisms.
2.4 billion years ago: Earth’s atmosphere fills with oxygen. A million years
later Earth freezes over, creating the first “Snowball Earth.”
2 billion years ago: First evidence of eukaryotic cells—cells that contain internal
“organs” (organelles), including a DNA-containing nucleus. Recent discoveries
suggest multicellular life may have also developed during this time.
535 million years ago: Many different types of organisms evolve in a relatively short period of
time (a few million years) called the Cambrian Explosion. During this “explosion” the first true
vertebrate (animal with a backbone) appears.
500 million years ago: Plants begin to colonize land.
397 million years ago: The first animals with four legs (tetrapods) evolve. This is
the common ancestor of all creatures with two or four legs, including humans.
340 million years ago: The first amphibians develop.
310 million years ago: The four-legged animals, not including amphibians, split into two groups—
reptiles and “mammal-like” reptiles. Mammals eventually evolve from the second group.
250 million years ago: Dinosaurs evolve and begin to dominate Earth.
200 million years ago: The first mammals appear.
150 million years ago: Archaeopteryx,
“the first bird,” lives in Europe.
130 million years ago: The first flowering plants evolve.
60 million years ago: The first primates appear.
6.5 million years ago: Hominins—early ancestors of
humans—evolve from the other primates.
300,000 years ago: The first “modern” human—Homo sapiens—evolves in Africa.
Eo-archean
Paleo-proterozoic
Meso-proterozoic
Neo-proterozoic
Cambrian
Ordovician
Devonian
Carboniferous
Permian
Jurassic
Cretaceous
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
Triassic
Anthropocene: Age of Man
252.2 million years ago
PALEOZOIC
Silurian
2.5 billion years ago
4 billion years ago
Neo-archean
65.5 milion years ago
Paleo-archean
Meso-archean
541 million years ago
HADEAN
Mass Extinction event
Extinct
We live in the Holocene epoch, but
many scientists argue that human
impacts, like climate change and
increased extinction rates, place us
in a new epoch: the Anthropocene.