New Recipe for Life: Zinc & Zap
Two scientists are overturning the Miller icon of the origin of life – you know, the illustration in almost every textbook showing sparks zapping gases and amino acids emerging from the goo. That doesn’t wash any more, claim Armen Mulkidjanian (University of Osnabrueck) and Michael Galperin (U.S. National Institutes of Health). Instead, Astrobiology Magazine reported, they are thinking zinc. Why? Life needed a source of energy in the realistic atmosphere of the early earth where Miller’s experiment is doomed. Enter the “Zinc World” scenario for the origin of life: zinc and zap.
The two didn’t actually produce any prebiotic molecules in any plausible primordial conditions. They just looked at proteins thought to be “evolutionarily old” and found high proportions of zinc. Ever since the heyday of the Miller experiment in 1953, scientists have come to the glum conclusion that earth’s atmosphere was not like the gas in Miller’s flask. It was not reducing (it did not contain hydrogen and other energetic molecules). It most likely contained carbon dioxide, nitrogen and more neutral molecules. “Researchers who have repeated the Miller-Urey experiment under the new atmospheric assumptions, including Miller, have shown that this new mixture does not produce amino acids.”
To get around the problem, Mulkidjanian and Galperin are suggesting that zinc sulfide at hydrothermal vents might have provided the reactive potential needed to build biomolecules. The zinc in sunscreen, for instance, allows it to store light energy. “Mulkidjanian explains that, once illuminated by UV light, zinc sulfide can efficiently reduce carbon dioxide, just as plants do.” They didn’t mention that plants have sophisticated light-harvesting nanomachines to perform photosynthesis – one of the most complex systems in biology.
The two admitted that a lot of work will be needed to test the zinc theory. NASA astrobiologist Max Bernstein politely agreed: “Whether it will be adopted or not eventually I cannot say, but I expect that many will want to see experimental evidence of the viability of reactions consistent with the hypothesized scheme under prebiotic conditions.”
This joke of a hypothesis does not deserve even a dishonorable mention, but it does accomplish some good in a reverse way: (1) it tells readers that the Miller Myth has been falsified (even though this article included the obligatory icon as a kind of imprimatur), and (2) it illustrates once again that astrobiologists are pseudoscientific storytellers unburdened by the necessity of experimental proof in their quest to find the next Useful Lie (05/02/2003, 08/06/2006, 06/29/2007).