The most primitive tribes of Australia and Africa, like the Eskimos of today, have not yet reached finger-counting, nor do they have numbers in series. Instead they have a binary system of independent numbers for one and two, with composite numbers up to six. After six, they perceive only “heap.” Lacking the sense of series, they will scarcely notice when two pins have been removed from a row of seven. They become aware at once, however, if one pin is missing. Tobias Dantzig, who investigated these matters, points out (in Number: The Language of Science) that the parity or kinesthetic sense of
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