Echoes of Life: What Fossil Molecules Reveal about Earth by Susan M. Gaines

By Susan M. Gaines

In 1936 a German chemist pointed out yes natural molecules that he had extracted from historic rocks and oils because the fossil is still of chlorophyll--presumably from crops that had lived and died thousands of years some time past. It was once one other twenty-five years earlier than this perception was once built and the time period ''biomarker'' coined to explain fossil molecules whose molecular constructions may show the presence of differently elusive organisms and techniques. Echoes of Life is the tale of those molecules and the way they're illuminating the historical past of the earth and its existence. it's also the tale of the way a couple of maverick natural chemists and geologists defied the dictates in their disciplines and--at a time whilst the average sciences have been fragmenting into ever-more-specialized sub-disciplines--reunited chemistry, biology and geology in a typical pastime. The infrequent mix of rigorous technology and literary style--woven right into a old narrative that strikes clearly from the straightforward to the complex--make Echoes of Life a e-book to be learn for excitement and contemplation, in addition to schooling.

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Extra resources for Echoes of Life: What Fossil Molecules Reveal about Earth History

Sample text

1-billion-year-old Fig Tree Formation in South Africa. . Pristane, phytane, and a preponderance of 17-carbon n-alkane all implied that photosynthetic microbes had been present. In the Soudan shale, Meinschein tentatively identified ring compounds that seemed to be related to sterols like cholesterol—known constituents of the cell membranes of more complex eukaryotic organisms. But when did life begin? Were there any rocks old enough to have recorded a time before life imposed its order, a time when the only organic compounds on Earth comprised the random assortment made by abiotic chemical reactions?

They are, then, chemically indistinguishable until they interact with other asymmetric molecules, at which point they react differently, much as when two people try to shake hands right to left instead of right to right. The amino acids that make up proteins and enzymes are asymmetric—with a chiral carbon atom bonded to an amino group, an acid group, a carbon chain, and a hydrogen atom—and one of the most crucial, and inexplicable, steps in the origin and evolution of life is the adoption of just one configuration from each of the possible pairs.

And yet some fatty acids appeared to be surprisingly persistent. Petroleum geochemists found them in shales and crude oils, and for a time even postulated that fatty acids play a pivotal role in petroleum formation. Abelson and others found them in the Green River shale, and Kvenvolden found them in even older Cretaceous-age rocks. Like the n-alkanes, the fatty acids in the oils and ancient rocks posed a number of enigmas that couldn’t be explained by their known occurrence in organisms. Though the only known biosynthetic pathways for fatty acids produced mostly acids with an even number of carbon atoms, and these were by far dominant in organisms, the distributions of fatty acids in older oils and rocks didn’t seem to reflect this.

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