|4.6 billion years ago
|Formation of Earth
|Our planet initially formed from dust and gas left over after the formation of the Sun.
|4 billion years ago
|Appearance of Life (Prokaryotes)
|The first forms of life were simple cells (prokaryotes), which lacked a nucleus or any other cell organelles. They primarily lived in the ocean.
|~3.5 billion years ago
|Some of these early prokaryotic cells developed the ability to perform photosynthesis, which created oxygen as a byproduct.
|~2.7 billion years ago
|The steady production of oxygen by photosynthesizing bacteria started to gradually change the Earth’s atmosphere.
|~2 billion years ago
|More complex cells (eukaryotes) emerged that contained organelles, including a nucleus.
|~1.5 billion years ago
|Multicellular Life Begins
|Some eukaryotes evolved into multicellular organisms.
|~600 million years ago
|The first large, complex multicellular organisms appeared.
|541 – 485.4 million years ago
|There was a rapid diversification and increase in the number and variety of animal species. Many of the major groups of animals that exist today first appeared during this time.
|~360 million years ago
|Plants Colonize Land
|Plants developed adaptations that allowed them to survive and reproduce outside of water, leading to the colonization of land.
|350 – 300 million years ago
|Insects and Amphibians Emerge
|The first insects and amphibians evolved, diversifying life on land further.
|~252 million years ago
|Permian Mass Extinction
|This was the Earth’s most catastrophic extinction event, with as much as 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct.
|230 – 66 million years ago
|Age of Dinosaurs (Mesozoic Era)
|Dinosaurs were the dominant terrestrial vertebrates. This era saw the diversification of birds, mammals, and flowering plants.
|~66 million years ago
|The dinosaurs went extinct, possibly due to a large asteroid or comet impact. Mammals subsequently diversified.
|66 million years ago – present
|Age of Mammals (Cenozoic Era)
|Mammals became the dominant land animals and human beings eventually appeared.