One reason is that the metric system is based on the number ten. The metric system emerged in the late eighteenth century out of a need to bring standardization to measurement, which had up to then been fickle, depending upon the preference of the ruler of the day. But ten was important well before the metric system. Nicomachus of Gerasa (c. 60–c. 120), a second-century neo-Pythagorean from Judea, considered ten a “perfect” number, the figure of divinity present in creation with mankind’s fingers and toes. Pythagoreans believed ten to be “the first-born of the numbers, the mother of them all, the one that never wavers and gives the key to all things.” Shepherds of West Africa counted sheep in their flocks by colored shells based on ten, and ten had evolved as a “base” of most numbering schemes. Some scholars believe the reason ten developed as a base number had more to do with ease: ten is easily counted on fingers and the rules of addition, subtraction, multiplication, and division for the number ten are easily memorized.