Earliest known life forms

The earliest known life forms on Earth are putative fossilized microorganisms found in hydrothermal vent precipitates.[1] The earliest time that life forms first appeared on Earth is at least 3.77 billion years ago, possibly as early as 4.28 billion years,[1] or even 4.5 billion years;[3][4] not long after the oceans formed 4.41 billion years ago, and after the formation of the Earth 4.54 billion years ago.[1][2][5][6] The earliest direct evidence of life on Earth are microfossils of microorganisms permineralized in 3.465-billion-year-old Australian Apex chert rocks.[7][8]

For the "Origin of life", see Abiogenesis, Astrobiology, Biogenesis, and Panspermia.
"Earliest life" redirects here. For non-scientific views of the earliest life, see Creation myth.
This article is about things that were once living. For other uses, see Lifeform (disambiguation). For longest lifespans, see List of longest-living organisms.
Evidence of possibly the oldest forms of life on Earth have been found in hydrothermal vent precipitates.[1][2]

Biosphere

Currently, Earth remains the only place in the universe known to harbor life.[9][10] The Earth's biosphere extends down to at least 19 km (12 mi) below the surface,[11][12][13][14] and up to at least 76 km (47 mi)[15] into the atmosphere,[16][17][18] and includes soil, hydrothermal vents, and rock.[19][20] Further, the biosphere has been found to extend 800 m (2,600 ft; 0.50 mi) below the ice of Antarctica,[21][22] and includes the deepest parts of the ocean,[23][24][25] down to rocks kilometers below the sea floor.[24][26][27] In July 2020, marine biologists reported that aerobic microorganisms (mainly), in "quasi-suspended animation", were found in organically-poor sediments, up to 101.5 million years old, 250 feet below the seafloor in the South Pacific Gyre (SPG) ("the deadest spot in the ocean"), and could be the longest-living life forms ever found.[28][29] Under certain test conditions, life forms have been observed to survive in the vacuum of outer space.[30][31] The total mass of the biosphere has been estimated to be as much as 4 trillion tons of carbon.[32] According to one researcher, "You can find microbes everywhere – [they are] extremely adaptable to conditions, and survive wherever they are."[24]

Of all species of life forms that ever lived on Earth, over five billion,[33] more than 99%, are estimated to be extinct.[34][35] Some estimates on the number of Earth's current species range from 10 million to 14 million,[36] of which about 1.2 million have been documented and over 86 percent remain undescribed.[37] However, a May 2016 scientific report estimates 1 trillion species currently on Earth, with only one-thousandth of one percent described.[38] Additionally, there are an estimated 10 nonillion (10 to the 31st power) individual viruses (including the related virions) on Earth, the most numerous type of biological entity,[39] and which some biologists consider to be life forms.[40] Moreover, there are more individual viruses than all the estimated stars in the universe;[41] which, in turn, are considered to be more numerous than all the grains of beach sand on planet Earth.[42] About 200 virus types are known to cause diseases in humans.[41] Other possible virus-like forms, some pathogenic, less likely to be considered living, much smaller than viruses and possibly much more primitive, include viroids, virusoids and prions.[43]

NASA scientists study earliest known life forms on Earth
Stromatolites studied in the Pilbara region of North West Australia
Related video: 3:03

Earliest life forms
Archaea, prokaryotic microbes, were first found in extreme environments, such as hydrothermal vents.

The age of the Earth is about 4.54 billion years;[44][45][46] the earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago.[47][48][49] There is evidence that suggests life began as early as 4.5 billion years ago.[3][4]

A December 2017 report stated that 3.465-billion-year-old Australian Apex chert rocks once contained microorganisms, the earliest direct evidence of life on Earth.[7][8] A 2013 publication announced the discovery of microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia.[50][51][52][53] Evidence of biogenic graphite,[54] and possibly stromatolites,[55][56][57] were discovered in 3.7 billion-year-old metasedimentary rocks in southwestern Greenland, and described in 2014 in the journal Nature. Potential "remains of life" were found in 4.1 billion-year-old rocks in Western Australia, and described in a 2015 study.[58]

The theory of panspermia suggests that life on Earth may have come from biological matter carried by space dust[59] or meteorites.[60]

A 2016 genetic study concluded that the last universal common ancestor (LUCA) may have lived in deep-sea hydrothermal vents 3.5 to 3.8 billion years ago.[61] A 2018 study from the University of Bristol, applying a molecular clock model, places the LUCA shortly after 4.5 billion years ago, within the Hadean.[3][4] In March 2017, fossilized microorganisms (microfossils) were announced to have been discovered in hydrothermal vent precipitates from an ancient sea-bed in the Nuvvuagittuq Belt of Quebec, Canada. These may be as old as 4.28 billion years, the oldest evidence of life on Earth, suggesting "an almost instantaneous emergence of life" after ocean formation 4.41 billion years ago.[1][2][5][6] Some researchers even speculate that life may have started nearly 4.5 billion years ago.[3][4] According to biologist Stephen Blair Hedges, "If life arose relatively quickly on Earth … then it could be common in the universe."[62][63][64]

As for life on land, in 2019 scientists reported the discovery of a fossilized fungus, named Ourasphaira giraldae, in the Canadian Arctic, that may have grown on land a billion years ago, well before plants were living on land.[65][66][67] In July 2018, scientists reported that the earliest life on land may have been bacteria 3.22 billion years ago.[68] In May 2017, evidence of microbial life on land may have been found in 3.48 billion-year-old geyserite in the Pilbara Craton of Western Australia.[69][70]

In January 2018, a study found that 4.5 billion-year-old meteorites found on Earth contained liquid water along with prebiotic complex organic substances that may be ingredients for life.[60][71]

Earliest known life forms (click "show" on right for more images)
Life on Earth
(view • discuss)
0.2 Mya
Humans
180 Mya
Flowers
200 Mya
Mammals
240 Mya
Dinosaurs
3500 Mya
Oxygen
4000 Mya
Microbes
4410 Mya
Water
4540 Mya
Earth
gollark: Pretty okay. I have some holiday time right nwo.
gollark: From Amazon, I mean, though maybe Waterstones has support for that too (never checked).
gollark: I mostly get ebooks anyway.
gollark: I have a signed How To book somewhere, since Waterstones happened to sell them signed.
gollark: https://what-if.xkcd.com/48/

See also

References
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