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See Inside April 2010

Readers Respond on "Expanding the Limits of Life"

Letters to the editor from the December 2009 issue of Scientific American


Lost Nucleotides
Although Alexander S. Bradley’s article “Expanding the Limits of Life” provides a fascinating account of the discovery of microbes in a previously unknown kind of hydrothermal vent ecosystem on the seafloor, it does not substantiate his claim that the findings hint that life may have originated in an environment like the Lost City hydrothermal vent.

Bradley suggests that Lost City produces “small organic acids such as formate and acetate” and that similar vents might have produced “simple organic acids” and “even more complex fatty acids” or “at least simple organic compounds.” Such statements do not begin to address the conditions and processes that led to the assembly of the nucleotides—adenine, guanine, cytosine, thymine and uracil—nor do the statements indicate that the materials necessary to form the nucleotides might be present in hydrothermal vents.

Studies of life in hydrothermal vents and of the chemistry of hydrothermal vents have provided no information about the evolution of RNA and DNA and of their nucleotides from inorganic and simple organic molecules.

Richard A. Ely
Dallas, Tex.

BRADLEY REPLIES: The reader calls attention to a long-standing question in origins of life research. Scientists widely agree that RNA preceded DNA as the molecule of heredity. But it is not clear whether RNA preceded or followed the origin of metabolism, which relies on the chemistry of much simpler organic compounds. Reconciliation of the geochemical requirements for the origins of RNA and metabolism has remained elusive—we do not yet have a theory for the origin of life. Until we do, sites like Lost City provide critical constraints on the range of potential prebiotic environments on Earth and beyond.

Zoned In
Having long argued that tradable rights and subleasing options are critical components of ocean zoning, I was encouraged to see these ideas displayed so prominently in “Zoning for Oceans” [Perspectives]. The ability to trade and negotiate encourages participation in what otherwise could be a very rigid top-down management approach. It can also encourage more efficient use of fish and other resources that are prone to shift over space and time, reducing the necessity during the design phase of trying to match the ecosystem scale with the policy scale—nearly impossible given the myriad socioeconomic and ecological considerations. For more details, please visit Resources for the Future (www.rff.org/oceanzoning).

James N. Sanchirico
Department of Environmental Science and Policy
University of California, Davis

The Incredible Mechanism
After the marvel, shock and awe of the Antikythera mechanism described by Tony Freeth in “Decoding an Ancient Computer,” there are more questions. This machine was obviously not a one-off or even the first of its kind; there had to be predecessors. Otherwise it would be as if someone 1,000 years from now found an Infiniti Q45 buried in mud and said we must have got tired of walking. We need to find the “Ardi” of the Antikythera.

Then there is the manufacturing. Making machine gears requires precision tools and considerable expertise. These were not Rolex watches, but they had to have a high level of precision to operate so many gears in the drive train. Below a certain level of precision the inefficiency of the gearing would make the whole thing inoperable. To make a large, thin gear on a shaft with very small gear teeth mesh without wobbling, run in both directions, and control dials and pointers several gear sets away without much play or lash requires a level of sophistication in metallurgy, machine design and precision machining on a level with the concept, design and purpose of this incredible mechanism.

Lowndes Whatley
Roswell, Ga.

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