- published: 06 Jun 2012
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The history of the Earth describes the most important events and fundamental stages in the development of the planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to the understanding of the main events of the Earth's past. The age of Earth is approximately one-third of the age of the universe. An immense amount of biological and geological change has occurred in that time span.
Earth formed around 4.54 billion years ago by accretion from the solar nebula. Volcanic outgassing likely created the primordial atmosphere, but it contained almost no oxygen and would have been toxic to humans and most modern life. Much of the Earth was molten because of extreme volcanism and frequent collisions with other bodies. One very large collision is thought to have been responsible for tilting the Earth at an angle and forming the Moon. Over time, such cosmic bombardments ceased, allowing the planet to cool and form a solid crust. Water that was brought here by comets and asteroids condensed into clouds and the oceans took shape. Earth was finally hospitable to life, and the earliest forms that arose enriched the atmosphere with oxygen. Life on Earth remained small and microscopic for at least one billion years. About 580 million years ago, complex multicellular life arose, and during the Cambrian period it experienced a rapid diversification into most major phyla. Around six million years ago, the primate lineage that would lead to chimpanzees (our closest living relatives) diverged from the lineage that would lead to modern humans.