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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 ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 6 January 2025. Problem of the lack of evidence for alien life despite its apparent likelihood This article is about the absence of clear evidence of extraterrestrial life. For a type of estimation problem, see Fermi problem. Enrico Fermi (Los Alamos 1945) The Fermi paradox is the discrepancy between the ...
The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia.
Earth's surface temperature will reach around 420 K (147 °C; 296 °F), even at the poles. [78] [94] 2.8 billion High estimate until all remaining Earth life goes extinct. [78] [94] 3–4 billion The Earth's core freezes if the inner core continues to grow in size, based on its current growth rate of 1 mm (0.039 in) in diameter per year.
It can also be termed as the zone of life on Earth, a closed system (apart from solar and cosmic radiation and heat from the interior of the Earth), and largely self-regulating. [95] Organisms exist in every part of the biosphere, including soil , hot springs , inside rocks at least 19 km (12 mi) deep underground, the deepest parts of the ocean ...
The Rare Earth hypothesis argues that planets with complex life, like Earth, are exceptionally rare.. In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity, such as sexually reproducing, multicellular organisms on Earth, and subsequently human intelligence, required an improbable combination of astrophysical ...
Big Historians point out that this limits study to the past 5,000 years and neglects the much longer time when humans existed on Earth. Henry Kannberg sees Big History as being a product of the Information Age, a stage in history itself following speech, writing, and printing. [25]
Earth is the only known place that has ever been habitable for life. Earth's life developed in Earth's early bodies of water some hundred million years after Earth formed. Earth's life has been shaping and inhabiting many particular ecosystems on Earth and has eventually expanded globally forming an overarching biosphere. [242]