Finger Counting

Finger counting is a human universal.  All cultures have been found to do some form of finger counting though the exact form varies and informs the culture.  Base numbers are formed via finger counting and some are not easily used for math nor are they intended to be used mathematically.  In some cases the numbers are not easily distinguished (other-thumb, other-finger, other-middle being used for six, seven, and eight is not uncommon but may present difficulty to  separate them as unique number words) and virtually any combination may be used but finger counting can be seen to this day in a variety of ways.  That is one of the unique things about counting technology - old methods may fade in importance but they never disappear completely.  To this day we still use finger counting, tallies, notched items, tokens,  and other counting methods exist side by side with our notation system.

Our time keeping system comes from a base 60 that can be counted quite easily on the fingers.  The thumb is not used in the count (it can be used to count) which starts with the first knuckle of the pointer finger and continues down before starting with the knuckle of the middle finger.  This is repeated for all fingers ending with the last knuckle of the pinky.  The other hand is used to show how many times twelve there are.  When all fingers and thumb are raised 60 is the result.

Base 10 is a system we are most familiar with.  Each digit represents a single number without use of multiplication.  Even this can vary in use, with starting from thumb or pointer finger being the most common.  The knuckles may also be used to count tactilely, though this is less common.  Full hands are therefore 10 and our number system reflects that by changing every ten numbers.  Like the Base 60 system shown above Base 10 systems also end at 9 and loop back to 1 with placeholders showing the total loops.

Base 10 and Base 60 have two things in common.  Both use only hands to count and both are able to be used arithmetically.  Neither are required functions of finger counting.  A good example of this is the Base 27 system used by the Oksapmin in Papua New Guinea.  This counting system starts at the thumb and ends at the opposite thumb but includes arms, shoulders, and head as parts to be counted.  It was later adapted to be able to perform arithmetic when western influence changed their traditional lifestyle but it retained the Base 27 system and was often used alongside other notational systems. 

Notaby, the Oksapmin use the "other" system for counting.  Their numbers are as follows:

As you can see the number words repeat  themselves with the "tan-" prefix.  This is a common method of number creation and shows an example of compound words.

With finger counting as a universal why would other forms need to develop?  Fingers, though innate, are very limited.  Not just in amount (as you saw finger counting can go up to 60 without aid), but in the amount of attention that they require.  As pointed out by Overmann et all (Bootstrapping Ordinal Thinking, 2017 Overmann et all) finger counting cannot be distributed across time and distance, handle extremely large or complex numbers, or be in use when the attention of the user is pulled elsewhere.  You cannot handle an object while showing your count nor is more than simple arithmetic possible.  Finger counting may have started humanity on the road to counting but the limitations on it pushed them into external artifacts such as notched bone, tallies, and knotted string to continue.