Earliest known life forms
Earliest known life forms: at least 3.5 billion years old, with possible traces back to 4.1 billion years.
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The earliest known life forms on Earth are at least 3.5 billion years old, possibly as early as 4.1 billion years ago, based on evidence from graphite in a zircon grain, stromatolites, and microfossils.
Lore & Background
The earliest evidence of life is 4.1-billion-year-old biologically fractionated graphite inside a single zircon grain from the Jack Hills range of Australia. The earliest evidence in a stratigraphic unit is 3.7-billion-year-old metasedimentary rocks containing graphite from the Isua Supracrustal Belt in Greenland.
The earliest directly known life are stromatolite fossils from 3.48-billion-year-old geyserite in the Dresser Formation of the Pilbara Craton, Western Australia. Microfossils have been found in 3.465-billion-year-old Apex chert rocks from the same region and in 3.42-billion-year-old hydrothermal vent precipitates from Barberton, South Africa. The earliest time for the origin of life is at least 3.5 billion years ago and possibly as early as 4.1 billion years ago—not long after the oceans formed 4.5 billion years ago and after the formation of the Earth 4.54 billion years ago.
Reader's Guide
The oldest undisputed evidence of life dates from at least 3.5 billion years ago according to the stromatolite record. The earliest direct evidence of life are stromatolites found in 3.48-billion-year-old chert in the Dresser formation. The 3.48 Ga Dresser formation also hosts microfossils of prokaryotic filaments in silica veins, the earliest fossil evidence of life on Earth. The 3.43 Ga Strelley Pool Formation in Western Australia hosts stromatolites that demonstrate vertical and horizontal changes, suggesting anoxygenic or oxygenic photosynthesis has been occurring since at least that time.
Frequently Asked Questions
What are the earliest known life forms?
They refer to the first microbial organisms that appeared on Earth, primarily prokaryotic cells capable of building layered structures like stromatolites. These tiny, single-celled ancestors mark the very beginning of the biosphere.
Where was the oldest fossil evidence of early life discovered?
Key sites cluster in Western Australia: the Dresser Formation in the Pilbara Craton yielded 3.48-billion-year-old stromatolites, and the nearby Apex chert produced 3.465-billion-year-old microfossils. Graphite grains from the Jack Hills in the same region also preserve carbon signatures that may predate both.
More in Taxonomy & Evolution
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Earliest known life forms (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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