The Problem of Fantasy

One of the big problems in modern fantasy novels is that the writers rarely do the necessary research to understand the state of pre-industrial societies. Law Dog gives an example of this with his discussion of grocers.

I offered my opinion that it was for the same reason that many cultures use a base twelve system -- 12 signs in the Zodiac, 12 inches to the foot, two x 12 hours in a day, five x 12 seconds in a minute, same number of minutes in an hour, so on and so forth -- twelve is the highest number that can be counted to using one hand, and 144 is the highest number that can be counted to using both hands.

He goes on to explain how you do this using your thumb and the bones on your fingers. One commenter explains how you can actually count to 16 on one hand using knuckles which might explain the difference between some archaic unit types (like US vs. Imperial measures).

12 also has the advantage that it is easily divisible without complex tools. It can be cut in half or thirds. You can cut those in half again to make fourths or sixths. With 16, you can get subdivisions simply by cutting it in half repeatedly. And people are pretty good at cutting things in half.

Nobody used base ten. Why? Because dividing things by five or ten is hard without using relatively modern tools. Most of the scientific equipment of the Renaissance is all base two. Fahrenheit was supposed to be base two with freezing water at 32 and body temperature at 96. This gave Fahrenheit 64 (2^6) graduations between his calibration points.

Many early units of measure also had very practical values. A foot or hand was based on anatomy. A barleycorn or poppyseed were length units based on the size of a common seed pod. A furlong (660 feet) was the distance plow team could work without taking a break. An acre is an area one furlong by a surveying chain wide, it is approximately how much land could be plowed in a day. A league (3 miles) was how about how far a person could walk in an hour. Very practical, but not very standardized.

Unfortunately most modern fantasy seems to stick with base ten. This is practical in that the readers can understand it, but unrealistic in that nobody with a medieval level of science and technology would actually be able to use such a thing. Similar things happen with sexual relations and religion. Far far too modern for the setting.