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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 ...
At long irregular intervals, Earth's biosphere suffers a catastrophic die-off, a mass extinction, [9] often comprising an accumulation of smaller extinction events over a relatively brief period. [10] The first known mass extinction was the Great Oxidation Event 2.4 billion years ago, which killed most of the planet's obligate anaerobes.
The transition from non-life to life has never been observed experimentally, but many proposals have been made for different stages of the process. The study of abiogenesis aims to determine how pre-life chemical reactions gave rise to life under conditions strikingly different from those on Earth today.
The history of life on Earth traces how organisms have evolved from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and all life on Earth, both living and extinct, descended from a last universal common ancestor that lived about 3.5 billion years ago .
All life on Earth—including humanity—shares a last universal common ancestor (LUCA), [9] [10] [11] which lived approximately 3.5–3.8 billion years ago. [12] The fossil record includes a progression from early biogenic graphite [ 13 ] to microbial mat fossils [ 14 ] [ 15 ] [ 16 ] to fossilised multicellular organisms .
Nickelback may be part of the reason we have life on Earth. Now, the researchers weren’t just super into late-90s Canadian hard rock—there’s a scientific reason behind the moniker.
The first eon in Earth's history, the Hadean, begins with Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of Earth's crust and Earth itself.
The oldest clear evidence of life on Earth dates to , although there have been reports, often disputed, of fossil bacteria from and of geochemical evidence for the presence of life [ 18 ] [ 83 ] Some scientists have proposed that life on Earth was "seeded" from elsewhere , [ 84 ] [ 85 ] [ 86 ] but most research concentrates on various ...