[asa] Origins of Life

From: Randy Isaac <randyisaac@comcast.net>
Date: Thu Jun 04 2009 - 16:23:57 EDT

The frequent posts on the topic of the origin of life finally prompted me to listen to the Teaching Company course entitled Origins of Life, taught by Prof. Robert Hazen from George Mason U/Carnegie Institution of Washington. He's a geologist who has devoted his career to the study of the origins of life and wrote, among others, the book "Genesis: The Scientific Quest for Life's Origins" http://hazen.ciw.edu/publications/books. I've just listened to the first half dozen or so lectures but I'm already very impressed with his balanced and professional approach. Two concepts from his early lectures are noteworthy for this list, I think.

First of all, in discussing the definition of life, he stresses the gradual, virtually seamless transition from non-life to life. He notes that once-sharp distincions between plants and animals or single-celled and multi-celled organisms have become blurred. He says "I believe that any attempt to formulate an absolute definition of life, any definition that makes a sharp distinction between life and non-life, must represent a similar false dichotomy. Here's why I say that, I think it's obvious that the first living cell did not just appear fully formed, with all its chemical complexity and genetic machinery intact. Rather, I suspect that life must have arisen through a step-wise sequence of emergent events. I see life's origin as a process of increasing chemical complexity. That process began with diverse processes of molecular synthesis in a variety of environments. Synthesis was followed by the selection, concentration, encapsulation, and organization of those molecules into diverse molecular structures. Next was the emergence of self-replicating molecules of increasing complexity and mutability. Then, self-replicating molecular systems evolved through the process of natural selection, driven by competition for limited raw materials. That sequential process provides the organizing theme for much of this lecture series."

I mainly want to note the emphasis on the gradual rather than sudden transition. This is similar to the message Denis Lamoureux emphasizes in his book Evolutionary Creation when he repeatedly notes the gradual transition from non-human to human, embryo to human, etc. In his polysyllabic words, "...gradual polygenism vs punctiliar monogenism".

The second aspect of note were the two lectures he devotes to two particular scientific announcements in the last dozen years or so. He articulates very well the essence of the scientific method, the role of subjectivity in science, and the importance of peer review. The first incident was the NASA announcement of the discovery of life on Mars. Published to great fanfare in Science in 1996, the analysis of the meteorite from Mars dubbed ALH84001, found in the Allan Hills region of Antarctica, NASA claimed to have discovered evidence of life on Mars. The relevant peer review in this case is not whether or not to publish in a noted journal, but the response of colleagues. One of the most vocal critics reviewing the findings was UCLA paleontologist William Schopf. In his book published in 1999, "Cradle of Life", he criticized the NASA team for inadequate analysis. Today that "discovery" is no longer credible.

The other announcement was by Schopf himself back in 1993 when he claimed to have discovered the oldest fossil evidence for life on earth. He identified single cells in Apex Chert in Australia, dating to 3.465 bya. Schopf was known to be a very scrupulous and careful scientist and his findings were widely accepted. Until another paleontologist, Martin Brasier, reexamined the fossils and challenged Schopf on every point of analysis in what Hazen describes a "dramatic high on April 9, 2002, at the second biennial NASA Astrobiology Science Conference." (Were any of you paleontologists at that meeting?) Today, the conflict is not definitively resolved but the two scientists have turned it into a constructive channel for vigorously searching for new fossils.

These are quite dramatic examples of how science works. The intense desire to be the first to find evidence of life leads to dramatic announcements and tremendous hype while any extraordinary claim draws extraordinary close examination. I recall reading about the above announcements but, not being active in the field, I hadn't appreciated the way in which it had played out in the scientific community.

Randy

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Received on Thu Jun 4 16:24:45 2009

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