Why did Egyptian civilization develop where and when it did? Tendency is to look for human causes for human events. For example, both the rise of agriculture in Egypt and the development of civilization has been attributed to cultural diffusion from earlier agriculture-based civilizations to the east, e.g., Mesopotamia. Modern research indicates clearly however, that both agriculture and Egyptian civilization are indigenously African and that both are linked inextricably to, and are in large part driven by, changes in critical environmental factors. The geologic record preserves evidence of those events, and deciphering the geologic record significantly deepens our understanding of our human past. The underlying geoscience principles and data that I’m going to describe in the following slides are accessible to students with little background in geoscience. Barbara Tewksbury, Hamilton College

Why did Ancient Egyptian civilization develop where it did? Presence of the Nile Nile is only trans-Saharan river Seasonal rainfall in high areas of East Africa plus topography that directs water west and north Nile hasn’t always been there: no Nile from ~1.8-0.8 million yrs ago Data from rock record allows us to reconstruct why Modern Nile results from tectonic uplift and tilting of areas in East African Rift starting ~800,000 years ago The Nile is critical. Without the Nile, Egypt would look like the rest of the Sahara.

Why did Ancient Egyptian civilization develop where it did? Bedrock geology Soft sedimentary bedrock (yellow) eroded easily into wide floodplains Navigable Nile for 1000 km N of First Cataract at Aswan Fertile soil carried downstream by Blue Nile from volcanics (purple) of Ethiopian Highlands Upper Nubia, Kerma, Meroe also in sedimentary stretches

Why did Ancient Egyptian civilization develop when it did? Climate change – sea level rose at end of last Ice Age 18,000 years ago, sea level was 125 m lower Delta surface high & dry Sea level rose rapidly until about 8,000 years ago, inundating Delta Since 8000 years ago deposition of fertile sediments has kept pace with sea level rise –agriculture developed

Why did Ancient Egyptian civilization develop when it did? Climate change & sea level rise Changing environments recorded in cores of Delta sediments Nile Delta suitable for agriculture only after about 8000 years ago (6000 BCE) Agriculture developed on other major deltas of the world as well Long-term Nile floodplain fertility tied to continued sea level rise - floodplain has risen ~5 m since 1700 BCE Agriculture indigenous, not by cultural diffusion from Mesopotamia – illuminated by the geologic record.

Why did Ancient Egyptian civilization develop when it did? Climate change – rainfall changes in the Sahara 6000-8000 BCE, Sahara was wetter than today Recorded in types of sediments, fossils of animals and plants Neolithic people lived across Sahara Nile floods “wild”

Why did Ancient Egyptian civilization develop when it did? Climate change – rainfall changes in the Sahara ca. 5000 BCE, sharp decline in rainfall and Neolithic sites in Western Desert Appearance of Neolithic sites in Delta and Nile Valley Climate change documented in the sediment record of paleolakes in the Sahara Sahara became uninhabitable about when Nile Valley & Delta became habitable and farmable In less than 2000 years, culture changed from isolated Neolithic settlements to villages to kingdoms to a unified empire stretching for 1000 km from Aswan to the Delta in 3050 BCE Bullet 6 – linked to climate change; not cultural diffusion from an older civilization. The pictureis not complete without the environmental picture, and it is the geologic record that allows us to reconstruct the environmental picture.

Predicting the future Geologic record indicates cooler worldwide temperatures (e.g., last Ice Age) correlate with less rainfall in Sahara Warmer was wetter in Sahara as recently as 6000 BCE Counterintuitively, geologic record suggests that global warming might “green” the Sahara The geologic record is also the only record we have that gives us a shot at predicting the future. These are good topics to accomplish our goal, which is to enable students to use geoscience concepts, methods, and data to address culturally/societally relevant questions in an African/Pan-African context.