Depictions of animals on ancient Egyptian artifacts could help scientists put together a record of the large mammals present in the Nile Valley over the past 6,000 years. The findings suggest a drying climate and human overpopulation has destabilized the ecosystem.
The study pointed out a steady decline in the stability of animal communities in the Nile Valley. Back when there were more animal species, the decline of one population did not make much of a difference; now that diversity has thinned, the ecosystem is much more sensitive, the University of Bristol reported.
About six millennia ago, there were 37 species of large-bodied mammals in Egypt, but today only eight remain. Some animals depicted in ancient Egyptian artwork that can no longer be found in the region today include "lions, wild dogs, elephants, oryx, hartebeest and giraffe."
"What was once a rich and diverse mammalian community is very different now," said first author Justin Yeakel. "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 study started in 2010 when Yeakel went to a Tutankhamun exhibition in San Francisco with co-author Nathaniel Dominy, then an anthropology professor at UC Santa Cruz. It was also inspired by the book "The Mammals of Ancient Egypt," by zoologist Dale Osborn.
"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 Osborn's book, and we started thinking about how we could take advantage of those records," Yeakel said.
The team identified five episodes over the past 6,000 years when dramatic changes took place in
Egypt's mammalian community, three of which were linked to extreme environmental changes. These drying periods coincided with upheaval in the human society such as the collapse of the Old Kingdom about 4,000 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 shift in community took place about 100 years ago. The analysis showed species extinctions over the past 150 years had a disproportionately large impact on ecosystem stability.
"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."
The findings were published in the Proceedings of the National Academy of Sciences (PNAS).
