memorization of so many signs, the Sumerians also used base 10 like steps of a ladder
between the various orders of magnitude. For example, the numbers followed the
sequence 1, 60, 60^2 , 60^3 , and so on. Each one of the iterations had a specific name,
making the numbering system extremely complex.
No one truly knows why the Sumerians chose such a high base number. Theories
range from connections to the number of days in a year, weights and measurements,
and even that it was easier to use for their purposes. Today, this numbering system is
still visible in the way we tell time (hours, minutes, seconds) and in our definitions of
circular measurements (degrees, minutes, seconds).
How did the Sumerian written counting system change over time?
Around 3200 BCE, the Sumerians developed a written number system, attaching a spe-
cial graphical symbol to each of the larger numbers at various intervals (1, 10, 60,
3,600, etc.). Because of the rarity of stone, and the difficulty in preserving leather,
parchment, or wood, the Sumerians used a material that would not only last but
would be easy to imprint: clay. Each symbol was written on wet clay tablets, then
baked in the hot sunlight. This is why many of the tablets are still in existence today.
The Sumerian number system changed over the centuries. By about 3000 BCE, the
Sumerians decided to turn their numbering symbols counterclockwise by 90 degrees.
And by the 27th century BCE, the Sumerians began to physically write the numbers in
a different way, mainly because they changed writing utensils from the old stylus that
was cylindrical at one end and pointed at the other to a stylus that was flat. This
change in writing utensils, but not the clay, created the need for new symbols. The 7
HISTORY OF MATHEMATICS
Who were the Mesopotamians?
T
he explanation of who the Mesopotamians were is not easy because there are
many historians who disagree on how to distinguish Mesopotamians from
other cultures and ethnic groups. In most texts, the label “Mesopotamian” refers
to most of the unrelated peoples who used cuneiform (a way of writing numbers;
see below), including the Sumerians, Persians, and so on. They are also often
referred to as Babylonians, after the city of Babylon, which was the center of
many of the surrounding empires that occupied the fertile plain between the
Tigris and Euphrates Rivers. But this area was also called Mesopotamia. There-
fore, the more correct label for these people is probably “Mesopotamians.”
In this text, Mesopotamians will be referred to by their various subdivisions
because each brought new ideas to the numbering systems and, eventually, math-
ematics. These divisions include the Sumerians, Akkadians, and Babylonians.