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Before Darwin Re: "Before Darwin," in which Eric Smith argues that simple metabolic processes likely explain how life emerged,1 Wächtershäuser also made an argument that the reverse citric acid cycle is similar to the first metabolic pathway to evolve.2 However, carbon dioxide fixation hardly is "one of the most conserved reactions throughout the biosphere," as Smith says. " Science will never have all the answers to any question — so what?

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Re: "Before Darwin," in which Eric Smith argues that simple metabolic processes likely explain how life emerged,1 Wächtershäuser also made an argument that the reverse citric acid cycle is similar to the first metabolic pathway to evolve.2 However, carbon dioxide fixation hardly is "one of the most conserved reactions throughout the biosphere," as Smith says. "

To the contrary, a variety of pathways, reactions, and enzymes are being discovered3 that are used to fix CO2: RubisCO in the traditional Calvin cycle found in plants and many proteobacteria, the reverse Krebs cycle (tricarboxylic, TCA), reductive acetyl CoA pathway in methanogenes, the 3-hydroxypropionate pathway, and the 3-hydroxypropionate / 4-hydroxybutyrate cycle.

Peter Gogarten

University of Connecticut

Storrs, CT

gogarten@uconn.edu

I found the article disappointing. What good is it to use so many words to say so little about such an interesting topic? The author avoids considering core aspects of the subject, including the ...

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