Woese chose one of the subunits from the ribosome, a single machine part, so to speak, and compared its sequence across different species, from bacteria such as E. coli to yeast to humans. His findings were a revelation, and turned our world view on its head. He could distinguish between the bacteria and complex eukaryotes without any difficulty, laying out the branching tree of genetic relatedness within and between each of these magisterial groups. The only surprise in this was how little difference there is between plants and animals and fungi, the groups that most biologists have spent
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