For a more extensive discussion, see N. Gregory Mankiw, Macroeconomics, Fourth Edition (New York, N.Y.: Worth Publishers, 2000), pp. 90-97; or Olivier Blanchard, Macroeconomics, Second Edition (Upper Saddle River, N.J.: Prentice Hall, 2000), pp. 214-220.
There is a more extensive discussion in Macroeconomics, Fourth Edition.
During the Stone Age, these early farmers devised ways to make axes and other tools from the harder rocks in the area, and as time passed, permanent settlements began to be established in this sheltered backwater.