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Proceedings Paper

Searching for an alternative form of life on Earth
Author(s): P. C. W. Davies
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Paper Abstract

Biologists tacitly assume that all life on Earth descended from a common origin. This assumption is based on biochemical similarities and gene sequencing, which enables organisms to be positioned on a common tree of life. However, most terrestrial organisms are microbes, and it is impossible to deduce their biochemical nature from morphology alone. The vast majority of microbes remain unclassified, leaving open the possibility that some of them might be an alternative form of life, arising either from an independent origin, or representing a hitherto overlooked very ancient branch of the known tree. Thus there may exist an extinct, or even extant, shadow biosphere. I discuss various research proposals for locating and identifying "alien" organisms on Earth, both ecologically separate and ecologically integrated.

Paper Details

Date Published: 9 October 2007
PDF: 10 pages
Proc. SPIE 6694, Instruments, Methods, and Missions for Astrobiology X, 66940K (9 October 2007); doi: 10.1117/12.742355
Show Author Affiliations
P. C. W. Davies, The Beyond Ctr., Arizona State Univ. (United States)

Published in SPIE Proceedings Vol. 6694:
Instruments, Methods, and Missions for Astrobiology X
Richard B. Hoover; Gilbert V. Levin; Alexei Y. Rozanov; Paul C. W. Davies, Editor(s)

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