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Molecular Evolution: Proteins ‘Clock’ the Origins of All Creatures—Great and Small

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Science  26 Jan 1996:
Vol. 271, Issue 5248, pp. 448
DOI: 10.1126/science.271.5248.448


Using a “protein clock,” researchers have dated a basic split in the tree of life, between prokaryotes—cells without nuclei—and eukaryotes, to 2 billion years ago. The results, reported on page 470 of this issue, are at odds with some other studies, which have placed this division anywhere from 3.5 billion to 1.6 billion years ago. The scientists have also used this clock, based on differences among 57 different enzymes found in 15 groups of organisms from bacteria to baboons, to date the origins of all major groups of organisms on the planet.