Paleoclimatic data for the past 20,000 years in the Near East come from a variety of sources: lake sediment records, marine records, and a series of terrestrial deposits (cave sediments and alluvial deposits). Pollen records are the proxies for the reconstruction of vegetation, which shows a direct and relatively rapid response to climatic change. Pollen-based reconstructions of vegetation and climate have been carried out at a local scale through the study of cores from lake sediments, and at a regional scale through cores from the bottom of the Mediterranean Sea. One problem is that fossil pollen studies are concentrated in areas with lakes, which are mostly the northern part of the region (Map 8.2a).
Among other methods, the study of stable isotopes has provided information on past precipitation patterns. They are studied on cave speleothems,1 microorganisms in lake and sea bottom deposits, land snails, and teeth (Bar-Matthews et al. 1999; Goodfriend 1999). The signatures obtained through isotopes derive directly from the atmosphere, eliminating the noise of human impact, and that is an advantage over studies of pollen analysis.
The broad picture of paleoclimatic change varies from region to region, due to differences in latitude, altitude, proximity to the seas, and weather patterns. During the coldest phases of the Late Glacial Maximum (about 18,000-16,000 years ago) vegetation in the mountainous regions of Turkey and Iran was characterized by Artemisia (wormwood) steppe (Van Zeist and Bottema 1991). Although dry conditions were present in the northern part of the Near East, pollen records from the Ghab Valley in Syria and Lake Hula in Israel show an increase in oak forests. Climatic amelioration in most of the regions of the Near East, attested by the expansion of forests, occurred between 15,000 and 11,000 bp (before the present) as warmer conditions induced more rainfall (Blanchet, Sanlaville, and Traboulsi 1998). A relatively short, dry, and cool period is recorded in some areas of the Near East between 11,000 and 10,000 years bp. This event, usually correlated with the Younger Dryas in Europe, was characterized by the cooling of the atmosphere and the partial return to glacial conditions. Pollen records from the northern areas of the Near East show a reduction of forests (Bottema 1995), and lake records of the same region show low levels (Roberts and Wright 1993). Ironically, it is under the adverse climatic conditions of this dry phase that plant and animal domestication began. Some postulate that dry conditions stimulated plant cultivation among human groups that were already in the process of sedentarization (Henry 1989; Bar-Yosef and Belfer-Cohen 1992). Other scholars disagree with this view and propose an alternative scenario in which dry conditions forced ‘‘domesticable’’ wild plants to migrate to areas where human populations were already manipulating wild plants to increase food production (McCorriston and Hole 1991; Wright 1993).
After 10,000 years bp the picture changed as temperatures rose and rains increased. In particular, the period between 9,000 and 6,000 years bp has been recognized as the Holocene Climatic Optimum (Map 8.2b). During this phase, rains increased considerably in the Eastern Mediterranean region and even in inland areas as far as the
Zagros Mountains (Rossignol-Strick 1999; Van Zeist and Bottema 1991). In addition to the increased winter rains, summer rains occurred in some areas, as suggested by stable isotopes, which in turn point to the enhancement of both cyclonic rains from the Mediterranean in winter and the influence of monsoon rains originated in the Indian Ocean in summer (Blanchet, Sanlaville, and Traboulsi 1998; Bar-Matthews et al. 1999). Pollen diagrams from lakes in the mountains of Iran and Turkey show that woodlands and forests advanced over areas formerly occupied by steppes. However, despite woodland recovery, increased human activities slowed down the recovery of woodlands in some regions (Van Zeist and Bottema 1991). A similar scenario occurred in drylands, where increase of grasslands allowed more possibilities for farming and herding, thus adding more pressure on the environment of the steppes and deserts (Butzer 1995). During this humid stage, lake levels increased, especially the now dry playas of the deserts in the Sahara and the Arabian Peninsula, and the inland seas, the Aral and the Caspian (Butzer 1995). The overall amelioration of the climate during this phase stimulated the establishment of farming villages, and their subsequent growth into urban centers. Gradual desiccation has been observed after about 3500 bce, a process that eventually gave shape to the modern dry environments of the region.
World History
