Definition of "nomadism"

Like the Mesolithic age of 10,000-8000 B.C., the period 6000-4000 B.C. seems to be one of the fall of fortresses and the rise of pastoral nomadism.

1981, William Irwin Thompson, The Time Falling Bodies Take to Light: Mythology, Sexuality and the Origins of Culture, London: Rider/Hutchinson & Co., page 160