What is life? New answers to an age-old question in astrobiology

January 13, 2011, Mary Ann Liebert, Inc.
Astrobiology is the authoritative resource for the most up-to-date information and perspectives on exciting new research findings and discoveries emanating from interplanetary exploration and terrestrial field and laboratory research programs. The journal is published 10 times a year in print and online, and is the official journal of Astrobiology Society. Complete tables of content and a free sample issue may be viewed online. Credit: © Mary Ann Liebert Inc. publishers

Biologists have been unable to agree on a definition of the complex phenomenon known as "life." In a special collection of essays in Astrobiology, a peer-reviewed journal from Mary Ann Liebert, Inc., leaders in the fields of philosophy, science, and molecular evolution present a variety of perspectives on defining life. Tables of content and a free sample issue are available online.

Why is a definition of life so important yet so elusive? As David Deamer, Guest Editor and Research Professor of Biomolecular Engineering, University of California, Santa Cruz, writes in his Introduction, a definition is needed to help determine what is and is not life as scientists begin to develop artificial life forms in the laboratory and, in the future, dispatch exploratory rovers that investigate what appear to be life forms on other planets.

Mark Bedau, Reed College (Portland, OR) and the University of Southern Denmark (Odense), relies on the Program-Metabolism-Container (PMC) model to define minimal chemical life. He supports his belief that this integrated triad of chemical systems is all that is needed for a to maintain its existence, grow, reproduce, and evolve, in the essay entitled, "An Aristotelian Account of Minimal Chemical Life."

Antonio Lazcano, National Autonomous University of Mexico, and colleagues present an historical perspective of the many definitions of life put forth over the years and why they have been unsatisfactory, in the essay, "The Definition of Life: A Brief History of an Elusive Scientific Endeavor."

Steven Benner, Foundation for Applied and The Westheimer Institute for Science and Technology (Gainesville, FL), explores the various definitions of life popular in the astrobiology community and how each is connected to a "theory of life." In the essay "Defining Life," Benner describes how capable of might be useful as universal biosignatures.

Finally, an essay adapted from the writings of deceased Ukranian scientist Sergey Tsokolov asserts that feedback loops should be an essential component of any definition of life. Life could not exist in the absence of negative feedback, concludes Tsokolov in the essay "A Theory of Circular Organization and Negative Feedback: Defining Life in a Cybernetic Context."

David Deamer commented, "These essays represent a remarkable effort on the part of the authors. We asked them to address a question that has challenged some of the great minds in biology, including Schrödinger himself, who initiated the discussion in 1944 with his book entitled "What Is ?" Our authors rose to the challenge, and their ideas and perspectives are genuinely new. It was a pleasure to work with them and help them wrestle with this difficult and complex problem." Deamer is the new Senior Editor in charge of essays on timely topics for Astrobiology.

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not rated yet Jan 13, 2011
hmmmm... what IS life? I would put it as an organism that can reproduce in some way, takes and uses energy, grow/divide, and dies.

(the first and last being in my views the most important, make no mistake they're all important.)
not rated yet Jan 13, 2011
Let's call BS here.

"Superficially, this observation would seem to imply that pCO2 does not exert dominant control on Earth's climate at time scales greater than about 10 My. A wealth of evidence, however, suggests that pCO2 exerts at least some control [see Crowley and Berner (30) for a recent review]. Fig. 4 cannot by itself refute this assumption. Instead, it simply shows that the “null hypothesis” that pCO2 and climate are unrelated cannot be rejected on the basis of this evidence alone."

Calling this paper evidence of lack of correlation between pCO2 and temperatures is exactly what he cautions against. More anti-GCC nonsense.
5 / 5 (1) Jan 13, 2011
^^ wrong thread...
1 / 5 (1) Jan 14, 2011
When I look at this, all I see is an advertisement.

It is disguised as an abstract to a scientific article, and not even too well, at that. And it just so happens that the publication right now has a free sample issue to read on-line.

The content of this "article" is hardly more than the list of contents page. I hope PhysOrg has understood to charge appropriately for this "full-page" ad.

As a reader, I am not thrilled.
1 / 5 (1) Jan 16, 2011
hmmmm... what IS life? I would put it as an organism that can reproduce in some way, takes and uses energy, grow/divide, and dies.

(the first and last being in my views the most important, make no mistake they're all important.)

By that defintion, nano-robots are "alive" as would be the robots from the 1980's movie "Batteries Not Included".

For that matter, any self replicating system would be "alive" even if none of it's components individually meet the definition of life. Here thinking of the "factory" of self-replicating robots, such as the obelisks in the movie 2001, or the Star Wars World Devastators.

Basicly any robot or system of robots capable of copying itself or making an improved version of itself would meet the defintion of "life".

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