Holocene climate change and its influence on early agriculture in the Nile Delta, Egypt

To investigate how Holocene climate patterns influenced the development of early Egyptian agriculture at the archaeological site of Sais on the Nile Delta, we conducted a palynological study. Seven palynological zones were defined to reveal Holocene climate fluctuations. Zone I (ca. 9000–7000 cal yr BP) was a period of warming climate, succeeded by a progressive drying climate phase in Zones II–VII (ca. 7000–2000 cal yr BP). Pollen records indicate Nile flooding prevailed before 7000 years ago, making the study area uninhabitable, before it later developed into a wetland setting. The earliest farming started at ca. 6700 cal yr BP, as indicated by the abrupt appearance of cereal (Poaceae > 35 μm), during a time of climate warming (Zone III), This material can be differentiated from wild Poaceae (<35 μm), which occurs throughout the profile, indicating the cereal was introduced to this area for agriculture. Results further reveal the transformation of human activities, from passive adaptation to climate, to actively remolding the environment against the background of long-term drying. During the early farming stage (ca. 6700–5500 cal yr BP), climate-human indicators were synchronous in distribution, suggesting lower pressure from climate change on population growth; however, this reversed from ca. 5500 cal yr BP, as intensive agriculture was required to meet shortages of natural resources during climate drying. Perhaps, the best evidence for adaptation is the increased abundance of Azolla from ca. 4000 years ago, a fern that favours growing in still-water bodies, hinting that much more irrigation was required at the time to sustain societal development.