Ancient pollen and charcoal preserved in deeply buried sediments in Egypt’s Nile Delta document the region’s ancient droughts and fires, including a huge drought 4,200 years ago associated with the demise of Egypt’s Old Kingdom, the era known as the pyramid-building time.
"Humans have a long history of having to deal with climate change," said Christopher Bernhardt , a researcher with the U.S. Geological Survey and a graduate of the University of Pennsylvania. "Along with other research, this study geologically reveals that the evolution of societies is sometimes tied to climate variability at all scales -- whether decadal or millennial."
Bernhardt conducted this research as part of his Ph.D. at Penn, along with Benjamin Horton , an associate professor in Penn’s Department of Earth and Environmental Science. Jean-Daniel Stanley at the Smithsonian Institution also participated in the study, published in July’s edition of Geology.
"The study geologically demonstrates that when deciphering past climates, pollen and other micro-organisms, such as charcoal, can augment or verify written or archaeological records -- or they can serve as the record itself if other information doesn’t exist or is not continuous," Horton said.
The researchers used pollen and charcoal preserved in a Nile Delta sediment core dating from 7,000 years ago to the present to help resolve the physical mechanisms underlying critical events in ancient Egyptian history.
They wanted to see if changes in pollen assemblages would reflect ancient Egyptian and Middle East droughts recorded in archaeological and historical records. The researchers also examined the presence and amount of charcoal because fire frequency often increases during times of drought, and fires are recorded as charcoal in the geological record. The scientists suspected that the proportion of wetland pollen would decline during times of drought and the amount of charcoal would increase.
And their suspicions were right.