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Published March 2011 | public
Journal Article

Monomer Abundance Distribution Patterns as a Universal Biosignature: Examples from Terrestrial and Digital Life


Organisms leave a distinctive chemical signature in their environment because they synthesize those molecules that maximize their fitness. As a result, the relative concentrations of related chemical monomers in life-bearing environmental samples reflect, in part, those compounds' adaptive utility. In contrast, rates of molecular synthesis in a lifeless environment are dictated by reaction kinetics and thermodynamics, so concentrations of related monomers in abiotic samples tend to exhibit specific patterns dominated by small, easily formed, low-formation-energy molecules. We contend that this distinction can serve as a universal biosignature: the measurement of chemical concentration ratios that belie formation kinetics or equilibrium thermodynamics indicates the likely presence of life. We explore the features of this biosignature as observed in amino acids and carboxylic acids, using published data from numerous studies of terrestrial sediments, abiotic (spark, UV, and high-energy proton) synthesis experiments, and meteorite bodies. We then compare these data to the results of experimental studies of an evolving digital life system. We observe the robust and repeatable evolution of an analogous biosignature in a digital lifeform, suggesting that evolutionary selection necessarily constrains organism composition and that the monomer abundance biosignature phenomenon is universal to evolved biosystems.

Additional Information

© 2011 Springer Science+Business Media, LLC. Received: 16 September 2010. Accepted: 3 January 2011. Published online: 21 January 2011. The research described in this work was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA), with support from the Director's Research and Development Fund (DRDF) and from the National Science Foundation under contract Nos. DEB-9981397, FIBR-0527023 and NSF's BEACON Center for Evolution in Action, under contract No. DBI-0939454. We thank Claus Wilke, Ronald V. Dorn III, and Diana Sherman for discussions. Finally, we are grateful to three anonymous reviewers for extensive and constructive comments on the manuscript.

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