Depictions of animals in ancient Egyptian artifacts have helped scientists assemble a detailed record of the large mammals that lived in the Nile Valley over the past 6,000 years. A new analysis of this record shows that species extinctions, probably caused by a drying climate and growing human population in the region, have made the ecosystem progressively less stable.
The study, published September 8 in Proceedings of the National Academy of Sciences (PNAS), found that local extinctions of mammal species led to a steady decline in the stability of the animal communities in the Nile Valley. When there were many species in the community, the loss of any one species had relatively little impact on the functioning of the ecosystem, whereas it is now much more sensitive to perturbations, according to first author Justin Yeakel, who worked on the study as a graduate student at the University of California, Santa Cruz, and is now a postdoctoral fellow at the Santa Fe Institute.
Around six millennia ago, there were 37 species of large-bodied mammals in Egypt, but only eight species remain today. Among the species recorded in artwork from the late Predynastic Period (before 3100 BC) but no longer found in Egypt are lions, wild dogs, elephants, oryx, hartebeest, and giraffe.
“What was once a rich and diverse mammalian community is very different now,” Yeakel said. “As the number of species declined, one of the primary things that was lost was the ecological redundancy of the system. There were multiple species of gazelles and other small herbivores, which are important because so many different predators prey on them. When there are fewer of those small herbivores, the loss of any one species has a much greater effect on the stability of the system and can lead to additional extinctions.”
The new study is based on records compiled by zoologist Dale Osborne, whose 1998 book The Mammals of Ancient Egypt provides a detailed picture of the region’s historical animal communities based on archaeological and paleontological evidence as well as historical records. “Dale Osborne compiled an incredible database of when species were represented in artwork and how that changed over time. His work allowed us to use ecological modeling techniques to look at the ramifications of those changes,” Yeakel said.
The study had its origins in 2010, when Yeakel visited a Tutankhamun exhibition in San Francisco with coauthor Nathaniel Dominy, then an anthropology professor at UC Santa Cruz and now at Dartmouth. “We were amazed at the artwork and the depictions of animals, and we realized they were recording observations of the natural world. Nate was aware of Dale Osborne’s book, and we started thinking about how we could take advantage of those records,” Yeakel said.
Coauthor Paul Koch, a UCSC paleontologist who studies ancient ecosystems, helped formulate the team’s approach to using the records to look at the ecological ramifications of the changes in species occurrences. Yeakel teamed up with ecological modelers Mathias Pires of the University of Sao Paolo, Brazil, and Lars Rudolf of the University of Bristol, U.K., to do a computational analysis of the dynamics of predator-prey networks in the ancient Egyptian animal communities.
The researchers identified five episodes over the past 6,000 years when dramatic changes occurred in Egypt’s mammalian community, three of which coincided with extreme environmental changes as the climate shifted to more arid conditions. These drying periods also coincided with upheaval in human societies, such as the collapse of the Old Kingdom around 4,000 years ago and the fall of the New Kingdom about 3,000 years ago.
“There were three large pulses of aridification as Egypt went from a wetter to a drier climate, starting with the end of the African Humid Period 5,500 years ago when the monsoons shifted to the south,” Yeakel said. “At the same time, human population densities were increasing, and competition for space along the Nile Valley would have had a large impact on animal populations.”
The most recent major shift in mammalian communities occurred about 100 years ago. The analysis of predator-prey networks showed that species extinctions in the past 150 years had a disproportionately large impact on ecosystem stability. These findings have implications for understanding modern ecosystems, Yeakel said.
“This may be just one example of a larger pattern,” he said. “We see a lot of ecosystems today in which a change in one species produces a big shift in how the ecosystem functions, and that might be a modern phenomenon. We don’t tend to think about what the system was like 10,000 years ago, when there might have been greater redundancy in the community.”
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The Stonehenge Hidden Landscapes Project, led by the University of Birmingham in conjunction with the Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology, is the largest project its kind.
Remote sensing techniques and geophysical surveys have discovered hundreds of new features, which now form part of the most detailed archaeological digital map of the Stonehenge landscape ever produced. The surprising results of the survey, unveiled in full at the British Science Festival, include 17 previously unknown ritual monuments dating to the period when Stonehenge achieved its iconic shape. Dozens of burial mounds have been mapped in minute detail, including long barrow (a burial mound dating to before Stonehenge) which revealed a massive timber building, probable used for the ritual inhumation of the dead following a complex sequence of exposure and excarnation (defleshing), and which was finally covered by an earthen mound.
The project has also revealed exciting new, and completely unexpected, information regarding previously known monuments. Among the most significant relate to the Durrington Walls ‘super henge’, situated just a short distance from Stonehenge. This immense ritual monument, probably the largest of its type in the world, has a circumference of over 1.5 kilometers (0.93) miles.
A new survey reveals that this had an early phase when the monument was flanked with a row large posts or tones, perhaps up to three meters high and up to 60 in number, some of which may still survive beneath the massive banks surrounding the monument. Only revealed by the cutting-edge technology used in the project, the survey has added yet another dimension to this vast and mysterious structure.
Novel types of monument were also revealed including massive prehistoric pits, some of which appear to form astronomic alignments, plus new information on hundreds of burial grounds, Bronze Age, Iron Age and Roman settlements and fields at a level of detail never seen before. Taken together, these results- which will be featured in a major new BBC Two series titled Operation Stonehenge: What Lies Beneath- show that new technology is reshaping how archaeologists understand the landscape of Stonehenge and its development over a period of more than 11,000 years.
In the year marking the centenary of the First World War, the new Stonehenge map even impacts on our knowledge of the momentous event. Surveys have produced detailed maps of the practice trenches dug around Stonehenge to prepare the troops for battle on the western front, as well as maps of RAF/RFC Stonehenge- one of Britain’s first military airbuses used by the Royal Flying Corps between 1917 and 1920.
British project leader Vincent Gaffney, Chair in Landscape Archaeology and Geomatics at the University of Birmingham, said: ‘The Stonehenge Hidden Landscapes Project is unique at a global level. Not only has it revolutionised how archaeologists use new technologies to interpret the past, it has transformed how we understand Stonehenge and its landscape.
‘Despite Stonehenge being the most iconic of all prehistoric monuments and occupying one of the richest archaeological landscapes in the world, much of this landscape in effect remains terra incognita.
‘This project has revealed that the area around Stonehenge is teeming with previously unseen archaeology and that the application of new technology can transform how archaeologists and the wider public understand one of the best-studied landscapes on Earth.
‘New monuments have been revealed, as well as new types of monument that have previously never been seen by archaeologists. All of this information has been placed within a single digital map, which will guide how Stonehenge and its landscape are studied in the future.
‘Stonehenge may never be the same again.’
Professor Wolfgang Neubauer, Director of the Ludwig Boltzmann Institute, said: Developing non-invasive methods to document our cultural heritage is one of the greatest challenges of our time and can only be accomplished by adapting the latest technology such as ground-penetrating radar arrays and high-resolution magnetometers. The developments of the Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology (LBI ArchPro) offer Europe the opportunity to carry out fundamental archaeological research at a scale and precision never previously attempted.
‘No landscape deserves to benefit from a study at this level of detail more than Stonehenge. The terabytes of digital survey data collected, processed and visualised by LBI ArchPro provide the base for the precise mapping of the monuments and archaeological features buried in the subsurface or still visible in the landscape surrounding Stonehenge. After centuries of research, the analysis of all mapped features makes it possible, for the first time, to reconstruct the development of Stonehenge and its landscape through time.’
The Stonehenge Hidden Landscapes Project is a collaboration between the University of Birmingham; Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology, Vienna and its international partners; University of Bradford; University of St Andrews; University of Nottingham, and the ‘ORBit’ Research Group of the department of Soil Management and the University Ghent, Belgium.
The project operates under the auspices of the National Trust and English Heritage.
Dr Nick Snashall, National Trust Archaeologist for the Avebury and Stonehenge World Heritage Site, said: ‘Using 21st-century techniques, the Stonehenge Hidden Landscapes team have transformed our knowledge of this ancient, precious and very special landscape. Their work has revealed a clutch of previously unsuspected sites and monuments showing how much of the story of this world-famous archaeological treasure house remains to be told.’
Dr Heather Sebire of English Heritage, Curator of Stonehenge, said: ‘This is such an exciting project. The surveys will help us form an understanding of possible new sites which have not been recorded before but which will need further investigation.’
Contributing Source: University of Birmingham
Header Image Source: WikiPedia
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