If pebbles or sticks are used instead of fingers, the system will probably be decimal.

But back of the stick and pebble counting the 10 natural counters always exist, and to them we must always look for the origin of this scale.
In any collection of the principal vigesimal number systems of the world, one would naturally begin with those possessed by the Celtic races of Europe.

These races, the earliest European peoples of whom we have any exact knowledge, show a preference for counting by twenties, which is almost as decided as that manifested by Teutonic races for counting by tens.

It has been conjectured by some writers that the explanation for this was to be found in the ancient commercial intercourse which existed between the Britons and the Carthaginians and Phoenicians, whose number systems showed traces of a vigesimal tendency.

Considering the fact that the use of vigesimal counting was universal among Celtic races, this explanation is quite gratuitous.