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The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
By the start of the Carboniferous Period, the Earth begins to resemble its present state. Insects roamed the land and would soon take to the skies; sharks swam the oceans as top predators, [83] and vegetation covered the land, with seed-bearing plants and forests soon to flourish.
The diversity of life forms did not increase significantly because of a series of mass extinctions that define widespread biostratigraphic units called biomeres. [159] After each extinction pulse, the continental shelf regions were repopulated by similar life forms that may have been evolving slowly elsewhere. [ 160 ]
Human history is the record of humankind from prehistory to the present. Modern humans evolved in Africa around 300,000 years ago and initially lived as hunter-gatherers.They migrated out of Africa during the Last Ice Age and had spread across Earth's continental land except Antarctica by the end of the Ice Age 12,000 years ago.
Evolutionary thought, the recognition that species change over time and the perceived understanding of how such processes work, has roots in antiquity. With the beginnings of modern biological taxonomy in the late 17th century, two opposed ideas influenced Western biological thinking: essentialism, the belief that every species has essential characteristics that are unalterable, a concept ...
Panspermia did not get much scientific support and deflects the need of an answer instead of explaining observable phenomena. Although interest in panspermia grew when traces of organic materials were found in meteorites, it is currently accepted that life started locally on Earth.
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Big History is the branch with the broadest scope, covering everything from the Big Bang to the present, incorporating elements of cosmology, geology, biology, and anthropology. [128] World history is another branch with a wide topic. It examines human history as a whole, starting with the evolution of human-like species. [129]