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Scientists debate life's origins

February 23, 2011

Renowned scientists in fields ranging from astrobiology to genetics disputed the origin of life on Earth as we know it and the definition of life itself during a panel discussion titled “The Great Debate: What is Life?” at Arizona State University on Feb. 12.

Many of the debaters agreed that the key to understanding our own origins and life itself was to find another example of life that evolved separate from our own. Although we may grasp how life has evolved on Earth, it is difficult to recognize how “non-life” became “life” when we have only one known example – our own – to study, according to Paul Davies, an ASU physicist and astrobiologist.

But where would we find life with a different origin from our own? The debaters suggested three possible places to search: On other planets, right here on Earth (“Life 2.0”), or created in a laboratory.

Chris McKay, a planetary scientist at the NASA Ames Research Center, suggested that we begin a search for life that is “not related to us at a fundamental level,” either genetically or biochemically, in outer space on “water worlds” like Europa or Enceladus. One advantage to this strategy would be that if we did find life elsewhere in the universe, this finding would imply that life is actually a common occurrence in the universe and, therefore, relatively abundant, said McKay.

Davies, who teaches in the Department of Physics at ASU’s College of Liberal Arts and Sciences, suggested that the search for a new kind of life should begin on Earth because searching our own planet is both cheaper and easier than searching others.

New life on Earth, commonly known as “Life 2.0,” might be found in one of two places: Beyond the reach of areas that are hospitable to known life, or, perhaps intermingled right next to our own kind of life.

Additionally, discovering a new origin of life on our own planet rather than elsewhere, such as Mars, would solve the Panspermia Hypothesis conundrum. This problem arises from the possibility that asteroids may have spread our own type of life to Mars or other planets and, therefore, that the life we may eventually discover there would have no different origins than our own, Davies said.

Nobel laureate Sidney Altman took a different route. “It doesn’t matter to know geographically where life started,” he said. Instead, he argued that what matters is to understand the chemistry of life and ask what will be the relevance of your experiments.

“The most important (aspect) is the chemistry,” Altman stressed.

J. Craig Venter, who created the world’s first genetically synthesized bacteria, hinted at a third method to study the origins of life: Create it in the laboratory. When his lab transformed a natural bacterium into a synthetic one in 2007, “it was the first one whose parent is a computer,” said Venter.

While some scientists at the Great Debate discussed where best to find a new origin of life, Leland “Lee” H. Hartwell, Nobel laureate and chief scientist at the ASU Biodesign Institute’s Center for Sustainable Health, tackled the definition of life or “how would we know it if we saw it?”

He argued that it would be difficult, if not impossible, to identify new forms of life on other planets. “We can’t expect the chemistry to look like what we know,” he said. Hartwell, however, put forward two characteristics necessary for the term “alive” to be bestowed upon a possible life form: The ability to replicate itself and the ability to metabolize substrates.

Additionally, alternative life forms would be sophisticated and complex, Hartwell said, since organisms compete with one another and improve over time.

Richard Dawkins, bestselling author of popular science books such as “The Selfish Gene” and “The God Delusion,” said the ability of life forms to “pass on the coded information that built them in the first place” was the key to distinguishing life from non-life. For example, some non-life entities such as a forest fire may still replicate themselves, spread and utilize energy. Instead, he defined life as something both highly statistically improbable and that retained a specific direction, such as the evolution guided by natural selection. The passing on of genes, consequently, gave life “it’s very very peculiar property” of having an “illusion of purpose,” or evolution, said Dawkins.

“The Great Debate: What is Life?” is the second in a series of great debates hosted by the ASU Origins Project, an ongoing initiative that addresses profound questions and topics meant to stir discussion.

Lawrence Krauss, the founding director of the ASU Origins Project and a Foundation Professor in physics and the School of Earth and Space Exploration, also participated in the discussion noting that attempts to find organisms on Earth outside the tree of life might necessarily fail.

The nucleic acids that form the basis of genetic inheritance may be composed the way they are for chemical and thermodynamic principles that would not permit any other molecule to perform that role, making any life form derived from a second genesis indistinguishable from those on the currently know tree of life.

In addition, any novel form of life could be “crowded out” from any ecological niche by already established organisms, he said, falling into extinction before it can gain a foothold on the planet.

“Darwin said it would be eaten by us,” Dawkins said in agreement.

“Yeah, but only if it’s tasty,” Davis quipped, noting that known organisms may not be able to metabolize life forms based on a radically different chemistry.

“The Great Debate” was sponsored by the ASU Origins Project in partnership with the Science Network, J. Epstein Foundation and the NASA Astrobiology Institute. Moderating the discussion was Roger Bingham of the Science Network. A videotape of the great debate is being edited by the Science Network and is planned to be available on the Web in March.

Written by Erin Lough and Erick O’Donnell with contributions by Serena Del Mundo, Ando Muneno, Allie Nicodemo, Maggie Pingolt, Noreen Qureshi and Cristina Rayas.

Carol Hughes,
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