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Evidence for Life on Earth before 3,800 Million Years AgoIt is unknown when life first appeared on Earth. The earliest known microfossils (approx. 3,500 Myr before present) are structurally complex, and if it is assumed that the associated organisms required a long time to develop this degree of complexity, then the existence of life much earlier than this can be argued. But the known examples of crustal rocks older than approx. 3,500 Myr have experienced intense metamorphism, which would have obliterated any fragile microfossils contained therein. It is therefore necessary to search for geochemical evidence of past biotic activity that has been preserved within minerals that are resistant to metamorphism. Here we report ion-microprobe measurements of the carbon-isotope composition of carbonaceous inclusions within grains of apatite (basic calcium phosphate) from the oldest known sediment sequences a approx. 3,800 Myr-old banded iron formation from the Isua supracrustal belt, West Greenland, and a similar formation from the nearby Akilia island that is possibly older than 3,850 Myr. The carbon in the carbonaceous inclusions is isotopically light, indicative of biological activity; no known abiotic process can explain the data. Unless some unknown abiotic process exists which is able both to create such isotopically light carbon and then selectively incorporate it into apatite grains, our results provide evidence for the emergence of life on Earth by at least 3,800 Myr before present.
Document ID
19980037618
Document Type
Contractor Report (CR)
External Source(s)
Authors
Mojzsis, S. J. (Scripps Institution of Oceanography La Jolla, CA United States)
Arrhenius, G. (Scripps Institution of Oceanography La Jolla, CA United States)
McKeegan, K. D. (California Univ. Los Angeles, CA United States)
Harrison, T. M. (California Univ. Los Angeles, CA United States)
Nutman, A. P. (Australian National Univ. Canberra, Australia)
Friend, C. R. L. (Oxford Univ. Oxford, United Kingdom)
Date Acquired
September 6, 2013
Publication Date
November 7, 1996
Publication Information
Publication: Nature
Volume: 384
Subject Category
Life Sciences (General)
Report/Patent Number
NAS 1.26:207592
NASA/CR-96-207592
Funding Number(s)
CONTRACT_GRANT: NAGw-2881
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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