The smell of a 2-billion-year-old earth

Life in the Paleoproterozoic Era consisted of microbes. The earth was already more than 2.5 billion years old, but dinosaurs as we know them would not evolve for another 1.65 billion years. Activity consisted of bacteria eating other bacteria – an act which has been deduced through chemical analysis, but only now has been visualized in the fossil record. Paleobiologist Martin Brasier of Oxford University in London and his colleagues created detailed, 3-dimensional images of microfossils in the Gunflint chert formation discovered 60 years ago on the north shore of Lake Superior. The cylindrical, photosynthetic Gunflintia microbes pumped the atmosphere full of oxygen, which paved the way for complex life. But the smaller, spherical bacteria which fed on them (IMAGE HERE) gave off carbon dioxide and hydrogen sulfide, which gave ancient earth an unmistakable odor. Brasier describes, "The whole world didn't smell of rotten eggs but if you had a sensitive nose, it would have been very widespread indeed."

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