The Ancient Romans had
weeks of eight days, called nundinae,
miles consisting of eight stadia or furlongs, and
their smallest military unit was the contubernium, consisting of eight men.
What was the reason behind this consistent eight-fold division ?
Using only the four fingers of both hands for "counting"1, to the exclusion of the thumbs ?
Computational ease or convenience, based on repeated division by two ?
Or perhaps something else2 entirely ?
1 I am not referring here to some systematic octal counting system, but rather only to an intuitive psychological inclination of creating small groups of four, five, eight, or ten items, based on the natural arrangement of fingers on each hand.
2 Including the distinct possibility that it might all be just a simple coincidence.