干旱区生态环境知识资源中心

The Egyptian civilization arose and developed during the Predynastic period (7300 to 5000 years before present or BP e.g. before 1950), synchronous with a large scale climatic event, the end of the African Humid Period. The decrease in the amount of precipitation associated with this climate change could have started earlier in Ethiopia (maybe as soon as 8000 BP), while other regions of tropical and subtropical Africa were affected between 6000 and 5000 BP. Several sources point to a maximum of aridity around 5200 BP. This event could have contributed to the concentration of population inside the Nile valley, and thus to the rise of the Egyptian civilization. After this event, the climate became generally arid but unstable, switching between aridity peaks (in particular at 4000 BP) and relative wetter conditions. Lastly, after 1500 BP, the amount of rainfall became very low but steady. Consequently, the climatic fluctuations could also have affected Egypt during the dynastic period (5000 to 2000 BP). Here, oxygen isotope composition (delta O-18 value) of phosphate was measured in bone and enamel of Egyptian mummies in order to track climate evolution between 5500 and 1500 BP. The delta O-18 values of mineralized tissues reflect the isotopic composition of the drinking water of studied individuals, i.e. the water from the Nile River for Egyptians. Estimated delta O-18 values of the past Nile river water increased at the end of the studied period. This marks a decrease in the amount of precipitation or an increase in local temperatures at the two source regions of the river, namely Ethiopia and the Equatorial Lake Plateau. These results confirm that the drying trend continued during the dynastic period and question its effect on the Egyptian prosperity.