The Urban Revolution, which Vere Gordon Childe gave a name to, like other revolutions in human history, happened at a cooling period. After the 8200 BP event, a long warm period known as Holocene Climate Optimum or Atlantic lasted until about 3000 BC. Then came a cool period that brought about civilizations. There is no name for this cool period. So I will call it “Subboreal Cool Period”, following the name of pollen zone divisions. Here is a graph of temperature fluctuation from 5000 BC to AD 200 reconstructed from oxygen isotope data of Greenland ice core.
Here is another graph of temperature fluctuation from 6000 BC to 400BC reconstructed from pollen assemblages preserved in a sediment core from northern Finland.
When the Subboreal Cool Period begins, regions from 35° north latitude southwards, such as Mesopotamia, the Nile Delta, the Indus plains and the southern China got cold and dry, while regions from 35° north latitude northwards, such as the Anatolian Plains and the Tibetan Plateau got cold and wet. It was this climate change that caused Sumerian, Egyptian, Indian and Chinese Civilizations to rise.
The Japanese meteorologist and geographer Hideo Suzuki has made the interesting suggestion that it was the refugee herdsmen and farmers from the increasing desert regions round about who were fated to become the slaves who made possible the intensive agriculture and the great building works for which ancient Egypt and the other river valley civilizations are famous.
The bottom of 2700 BC was the age of Urban Revolution, when these major civilizations flourished almost at the same time. Take the Sumerian Civilization for example. The precipitation in upper reaches of the Euphrates and the Tigris rivers increases, while that in their lowlands decreases. The rivers got swollen and the farmlands around them dried up. Farmers naturally rushed to the riversides to seek for irrigation water. But just gathering does not make civilization.
The word “civilization” comes from the Latin word “civis”, meaning townsman or citizen. The word “civis” was contrast with the Latin word “barbaria”, meaning barbarian, which further stemed from the ancient Greek word “βάρβαρος”, meaning a non-Greek. A non-Greek’s speech sounded “bar bar” to Greeks and “βάρβαρος” was an imitative word for the unintelligible babble. Can we say whether the communication media mediated people or not is the criterion for civilization?
The communication media, namely, language, money and punishment, had functioned to some degree, before the Civilizations emerged, but these media became important, when people gather together, resulting in high population density and high social entropy.
We can attribute the civilization/culture difference to that of urban/rural. The word “culture” comes from the Latin word “colere”, meaning “cultivate”. Neolithic Revolution was culture revolution, while Urban Revolution was civilization revolution. Both revolutions are characterized by centralization and intellectual sophistication, but Urban Revolution requires more centralization and intellectual sophistication because of the high population density.
Suppose people rush to the riversides to seek for irrigation water, as must have happened at the Subboreal Cold Period. They will quarrel with one another, struggling for water or harvest. This chaotic uncertainty increases social entropy and those who can control three media, language, money and punishment, that is to say, who have cultural, economical and political capital must intervene to reduce this social entropy.
The Civilizations I mentioned above disappeared or declined after 1800 BC. You can see the peak named Subboreal Warm Period in the graph above. After 1800 BC, the reverse of Subboreal cooling happened, that is to say, the regions from 35° north latitude southwards got warm and wet, while the regions from 35° north latitude northwards got warm and dry.
In the regions from 35° north latitude southwards got, precipitation increased and river flow decreased. Farmers do not have to depend on cities any longer. They left cities and scattered to the countries. On the other hand, nomads in the regions from 35° north latitude northwards migrated southward to seek for water. Some attribute the Dark Age after 1800 BC to the invasion and destruction by these nomads, the Civilization would have disappeared or declined without the migration of northern nomads. The Dark Age is so named not because it was the miserable age, but because there remained few written records of the age. As I stated before, at the warmer period, power is decentralized and intellectual stagnation takes place.
- ↑ Childe, V. Gordon (1950) The Urban Revolution. Town Planning Review 21:3-17
- ↑ Data from National Snow and Ice Data Center, National Oceanic & Atmospheric Administration, U.S. Department of Commerce (1997) GISP2 Bidecadal Oxygen Isotope Data
- ↑ Data from Seppa, H. and Birks, H.J.B. (2001) July mean temperature and annual precipitation trends during the Holocene in the Fennoscandian tree-line area: pollen-based climate reconstructions, The Holocene, Volume 11, Number 5, pp. 527-539.
- ↑ 鈴木秀夫 (1978) 気候と文明, 朝倉書店, p.1-69
- ↑ H. H. Lamb (1995) Climate, History and the Modern World, Second edition, Routledge, p.125. The people who were engaged in building the Pyramid were not slaves.