A hidden landscape we can no longer see could explain the mystery of the pyramids: ScienceAlert

Seeing the famous pyramids of Giza as they stand today – immovable, impenetrable fortresses surrounded by windswept sand and a sprawling metropolis – it’s hard to imagine the day they were built.

These stone labyrinths, built to honor the dead and transport them to the afterlife, were erected around 4,500 years ago without modern technology and with astonishing precision.

But the Egyptians needed more than a few primitive ramps to carry the extremely heavy blocks of stone into position.

A new study suggests that favorable environmental conditions allowed the construction of the Giza pyramids, with an ancient arm of the Nile serving as a navigable conduit for transporting goods.

“To build the pyramids, tombs and temples of the plateau, it now seems that the ancient Egyptian engineers took advantage of the Nile and its annual floods, using an ingenious system of canals and basins which formed a port complex at the foot of the Giza plateau,” physical geographer Hader Sheisha of the University of Aix-Marseille in France and his colleagues write in their article.

“However, there is little environmental evidence regarding when, where, and how these ancient landscapes evolved.”

Archaeologists for a time thought that Egyptian pyramid builders might have dredged the Nile’s waterways to form canals and harbors, harnessing the annual floods that would act as a hydraulic lift to transport building materials.

The port complex that archaeologists say served the pyramids of Khufu, Khafre and Menkaure currently lies more than 7 kilometers (or 4.3 miles) west of the present-day Nile. The creeks also had to be deep enough to keep stone-laden barges afloat.

Boreholes taken during urban engineering work around present-day Giza have provided stratigraphic evidence of rock layers consistent with an ancient branch of the Nile extending towards the base of the pyramids.

But questions remain about how the Egyptians designed water access to the Giza pyramids. At the time of their construction, northern Egypt was plagued by extreme climate change, with flash floods repeatedly ravaging the lost city of the pyramids, Heit el-Ghurab, which housed seasonal workers.

In this study, researchers turned to fossilized pollen grains to paint a more detailed picture of the river system as it flowed millennia ago. Pollen grains can be preserved in ancient sediments and have, in other studies, been used to reconstruct past climates and vegetated landscapes that look dramatically different today.

By extracting pollen grains from five cores drilled in the present-day Giza floodplain to the east of the pyramid complex, the team identified an abundance of grass-like flowering plants that line the banks of the Nile and the marsh plants that grow in lakeside environments.

This, they say, reveals the presence of a permanent body of water that crossed the Giza floodplain and swelled thousands of years ago.

From there, they traced the rise and fall of water levels in the Khufu branch of the Nile over 8,000 years of Egyptian dynastic history, linking their findings to other historical records.

“Our 8,000-year-old reconstruction of the Khufu Branch levels improves understanding of river landscapes at the time of the construction of the Giza pyramid complex,” Sheisha and colleagues write.

“The Khufu branch remained at a high water level… during the reigns of Khufu, Khafre and Menkaure, facilitating the transport of building materials to the pyramid complex of Giza.”

Location of cores (red dots) on the Giza floodplain. (Sheisha et al., PNAS2022)

But after the reign of King Tutankhamun, who ascended around 1349 to 1338 BCE, the Khufu branch of the Nile gradually declined until it reached its lowest documented levels in the last 8,000 years towards the end of the period. dynastic.

This fall correlates with chemical markers in the teeth and bones of Egyptian mummies that similarly suggest an arid environment, as well as other historical records.

As with all archaeological studies, however, the chronological date ranges – of pharaonic reigns and environmental changes – can vary widely, so we must take these results with a grain of salt.

But by linking environmental and historical data, the study provides much more direct evidence than when archaeologists searched for missing fractals – exquisite, self-repeating patterns often found in nature – to infer that ancient Egyptians could have dug river channels when building the Dahshur pyramids. , further south of Giza.

“It’s hard to believe the gigantic footprint left by the Egyptians,” said Arne Ramisch, a geologist at the University of Innsbruck. new scientist at the time.

The researchers behind this latest study suggest that similar approaches could be used to reconstruct ancient waterscapes that covered other Egyptian pyramid complexes, including the Dahshur necropolis, when these monumental edifices were constructed.

The research has been published in PNAS.

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