It is a common belief that we use a base 10 representation of integers because we have 10 fingers.

Does there exist historical evidence which supports the claim that this is true and that the number of fingers indeed was the major reason that we use 10 over similar candidates like 8 or 12?

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    $\begingroup$ Base 10 is used since very ancient times (probably pre-dates writing) and no justification of this base seems to exist except the number of fingers. There is also ample evidence, including written one that people really used fingers to count. The concluson seems inevitable. $\endgroup$ – Alexandre Eremenko Jul 22 '18 at 12:15
  • $\begingroup$ If "we" refers to all humans, I would quibble with the premise of the question, since numeral systems with bases other than ten are and have been in use. For example, there are vestiges of a base-20 system visible in various European languages: In French, 80 is quatre-vingts (four twenties); in Danish, 50 is halvtreds (shortened form of a longer word that literally translates as two-and-a-half twenties; even in English we have "score" as in "four score and seven years ago" = 87 years ago. $\endgroup$ – njuffa Jul 22 '18 at 16:49
  • $\begingroup$ @njuffa: Don't you think that base 20 is also based on fingers (and toes)? $\endgroup$ – Alexandre Eremenko Jul 23 '18 at 6:26
  • $\begingroup$ @AlexandreEremenko Absolutely. I upvoted your comment. I was challenging the "over similar candidates like 8 or 12" part of the question. While the decimal system is clearly dominant, other systems exist(ed), see the list in Wikipedia. I admit it's a somewhat nit-picky challenge :-) $\endgroup$ – njuffa Jul 23 '18 at 7:08
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    $\begingroup$ Placing two facts next to each other, the base and the number of fingers, does not establish a causal connection between the two. There are no historical records establishing it explicitly, and the commonly used "because" is not just speculative, but can only work in a very loose sense, if any. The same "because" would equally "explain" 5, or really any number from 2 to 10, or even 20, while the first positional system, Babylonian, had base 60. "We" use 10 because of a number of historical contingencies and cultural peculiarities involving Indians, Arabs, etc., it could easily be otherwise. $\endgroup$ – Conifold Jul 23 '18 at 23:11

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