as centers of innovation and artistic and scientific achievement, with complex
social orders and sophisticated political systems. Moreover, each hearth benefited
from regularly cultivated and proficient agricultural systems, often based on exten-
sive irrigation. The latter feature generally enabled the production of a surplus of
food. Most of the hearths developed on the banks of major rivers, or at least
in close proximity to streams, allowing for a regular supply of water, and also
benefited from the rich alluvial soils laid down by flooding.
Scholars generally recognize four major cultural hearths, and some include
three secondary hearths as well. The four major hearths are the Tigris-Euphrates
River Valley located in modern Iraq; the Nile River Valley in Egypt; the Indus
River Valley situated in modern Pakistan; and China’s Huang Ho River Valley.
The three secondary hearths are located in western Africa, especially Ghana and
its environs; Central America, especially southern Mexico, Belize, and northern
Guatemala; and the Gangetic Plain of northern India. Each of these locations wit-
nessed the emergence of a common set of advancements, either entirely in isola-
tion from the others or at least partially independent of external influences. The
common denominators in each included the organization of society into hierarchi-
cal classes, a division of labor ranging from manual labor to higher intellectual
pursuits, a high degree of urbanization, a relatively advanced transportation and
communication system, and a high level of skill in the physical and literary arts.
These characteristics appeared in part because of the food surplus made possible
by the rich soils and abundant supply of water. A significant percentage of the
workforce was freed from the task of cultivating crops, allowing them to develop
technical and scientific skills in areas as diverse as metallurgy, astronomy, and phi-
losophy. Religious belief and language both acquired more organization, complex-
ity, and sophistication. Religion became more interpretive and ritualistic, both
characteristics that were secured by the flowering of religious literature and a class
of religious officials in the form of priests or others who functioned as intermediaries
between humanity and the god(s). Skills inarchitecture and construction were
refined, as monuments either to the gods or to rulers (sometimes they were one and
the same) were raised in religious tribute. As new technology appeared and the liter-
ary arts flourished, the vocabulary of language became richer and its discourse deep-
ened, enabling speakers to express themselves in new and innovative ways.
Writing systems emerged independently in the hearth regions as early as 3000–
4000 BCE. Probably the first was early cuneiform in the Sumerian city-states
located in Mesopotamia, followed within a few centuries by an early form of
hieroglyphics in the lower Nile region in Egypt and in the Indus Valley in South
Asia. Writing systems were necessary for record-keeping and may have evolved
because of the increased commerce brought on by specialization of labor and
crafts and the need to record the quantities of grain produced in surplus years.88 Culture Hearth