Earliest Evidence For Life On Earth
The earliest identified organisms were minute and relatively featureless, and their fossils look like small rods, which are very difficult to tell apart from structures that arise through abiotic physical processes. The oldest undisputed evidence of life on Earth, interpreted as fossilized bacteria, dates to 3 Ga. Other finds in rocks dated to about 3.5 Ga have been interpreted as bacteria, with geochemical evidence also seeming to show the presence of life 3.8 Ga. However these analyses were closely scrutinized, and non-biological processes were found which could produce all of the "signatures of life" that had been reported. While this does not prove that the structures found had a non-biological origin, they cannot be taken as clear evidence for the presence of life. Geochemical signatures from rocks deposited 3.4 Ga have been interpreted as evidence for life, although these statements have not been thoroughly examined by critics.
Read more about this topic: Evolutionary History Of Life
Famous quotes containing the words earliest, evidence, life and/or earth:
“The founders of a new colony, whatever Utopia of human virtue and happiness they might originally project, have invariably recognized it among their earliest practical necessities to allot a portion of the virgin soil as a cemetery, and another portion as the site of a prison.”
—Nathaniel Hawthorne (1804–1864)
“Never say a humorous thing to a man who does not possess humour. He will always use it in evidence against you.”
—Herbert, Sir Beerbohm (1853–1917)
“There are some things which cannot be learned quickly, and time, which is all we have, must be paid heavily for their acquiring. They are the very simplest things and because it takes a man’s life to know them the little new that each man gets from life is very costly and the only heritage he has to leave.”
—Ernest Hemingway (1899–1961)
“I traveld thro’ a Land of Men
A Land of Men & Women too,
And heard & saw such dreadful things
As cold Earth wanderers never knew.”
—William Blake (1757–1827)