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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 ...
Early micro-fossils may have come from a hot world of gases such as methane, ammonia, carbon dioxide, and hydrogen sulfide, toxic to much current life. [230] Analysis of the tree of life places thermophilic and hyperthermophilic bacteria and archaea closest to the root, suggesting that life may have evolved in a hot environment. [ 231 ]
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.
Today, scientists agree that all current life descends from earlier life, which has become progressively more complex and diverse through Charles Darwin's mechanism of evolution by natural selection. Darwin wrote to J.D. Hooker on 29 March 1863 stating that "It is mere rubbish, thinking at present of the origin of life; one might as well think ...
The Paleozoic ("old life") era was the first and longest era of the Phanerozoic eon, lasting from 538.8 to 251.9 Ma. [105] During the Paleozoic, many modern groups of life came into existence. Life colonized the land, first plants, then animals. Two significant extinctions occurred.
Primordial soup, also known as prebiotic soup and Haldane soup, is the hypothetical set of conditions present on the Earth around 3.7 to 4.0 billion years ago. It is an aspect of the heterotrophic theory (also known as the Oparin–Haldane hypothesis) concerning the origin of life, first proposed by Alexander Oparin in 1924, and J. B. S. Haldane in 1929.
Pier Antonio Micheli, c. 1729, observed that when fungal spores were placed on slices of melon, the same type of fungi were produced that the spores came from, and from this observation he noted that fungi did not arise from spontaneous generation. [42] In 1745, John Needham performed a series of experiments on boiled broths. Believing that ...
The question does not include the timing of when anything came to exist. Some have suggested the possibility of an infinite regress, where, if an entity cannot come from nothing and this concept is mutually exclusive from something, there must have always been something that caused the previous effect, with this causal chain (either deterministic or probabilistic) extending infinitely back in ...