Ancient Reeds Whisper Secrets about China’s Great Wall
Scientists analyzing microscopic plant materials trapped within building materials on The Great Wall of China have derived volumes of information about ancient environmental and climatological conditions.
A team of archaeologists led by Dr. Robert Patalano of the Department of Archaeology, Max Planck Institute for Geoanthropology, has analyzed plant materials that were used in the construction of segments and beacon towers of the Great Wall in northwestern China.
According to a new study published in the journal Nature, site-specific analysis of organic archaeological building materials has provided “local paleoclimatic and environmental conditions at the time of building.” Furthermore, the researchers say their approach has laid a new foundation for further applications of advanced “molecular, biochemical, and isotopic technologies” relating to the environment, weather and climate.
Studies of plant material in the Great Wall of China are revealing information about ancient oases and climactic changes. Photo from Gobi desert, Dunhuang, China Source: dinozzaver / Adobe Stock
The Great Wall of China: A Wall of Many Parts across Space and Time
The Great Wall of China is testimony to the paradox of ‘my grandfather's axe', wherein the head and handle of an axe are worn out and replaced several times, but the object is still referred to as ‘my grandfather’s axe’, even though nothing of the original remains. So while one’s imagination might hold images of a massive Great Wall building project, it was in reality built, repaired, and restored by nine Chinese dynasties over 2,300 years.
The new study has provided supporting evidence for several earlier archaeological speculations about when certain parts of the wall were originally built and then altered or repaired. It was found that some of the walls and fortresses date all the way back to the Warring States period (475–221 BC). These sections were built with locally available reed fascines and bundles of wood, which the scientists said were “interbedded with gravel-mixed rammed earth ”.
Some of the oldest sections of the Great Wall of China date back to the 5th century BC, and were constructed with alternating sections of reed and rammed earth. Photo of sampling of phragmites culms from a wall section at Majuanwan (Site 7). (Robert Patalano / CC BY 4.0 )
Celebrating a Molecular World First
The study specifically looked at phragmite seed samples. This genus of large perennial reed grasses is found in wetlands throughout temperate and tropical zones around the world, and the ancient strains found within the Great Wall of China were compared to modern varieties. “For the first time,” according to the authors of the new paper, phragmites collected from fascines (bunches of reeds) used in the construction of the ancient Great Wall of China in modern-day Gansu and Xinjiang, “have been subjected to a combination of chromatographic techniques and isotope analyses.”
Now for the technical bit. The team applied techniques such as pyrolysis gas chromatography mass spectrometry (Py-GC-MS), lipid concentration and distribution, and bulk carbon and nitrogen isotope analysis. With scanning techniques such as electron microscopy, the researchers discovered that most of the ancient reed samples were in an “excellent” state of preservation.
The scientists were able to peer back in time and monitor historic environmental and climatological changes along the eastern margin of the Tarim Basin during the Han Dynasty (170 BC). It was observed that “significant surface-water hydrological changes” occurred only after the Song Dynasty (1160 AD), which was caused by regional climate change.
Remnants of Sishilidadun Beacon Tower dating to the Song Dynasty. Although not visible, the beacon tower was constructed like the nearby wall sections, with rammed earth alternating with reed fascines (Robert Patalano / CC BY 4.0 )
Mapping Ancient Environmental Changes with the Great Wall of China
The researchers write that “an array of fascine and rammed-earth ramparts was established following the unification of China in 221 BC.” The reason given for this was to protect against the threatening northern Xiongnu and Xianbei states. The paper says that in the 2nd Century BC these border defenses became essential in expanding the territories of the Han Dynasty from the central Chinese plains into the western frontier, including today’s Xinjiang and Gansu Province.
In conclusion, the new study highlights “the future potential of these in situ materials as valuable biogeochemical archives for studying human-altered ecosystems and hydrology”. In other words, by studying plant matter buried within ancient ram parts, a deeper understanding of environmental conditions at specific historical points along the Great Wall of China can be reached. Furthermore, the cause, rate, and timing of hydrological changes in ancient China is now much clearer.
Also, and equally as importantly, these new techniques of analysis can now be applied at any archaeological site, anywhere in the world, revealing novel evidence for not only for the source, but also the diversity of building materials that were used in ancient structures.
Top image: The Great Wall of China. Source: Li Ding / Adobe Stock
By Ashley Cowie
Patalano, R. et al. December 29, 2022. Ancient Great Wall building materials reveal environmental changes associated with oases in northwestern China . Nature. Available at: https://www.nature.com/articles/s41598-022-27071-4
Xie, S. December 23, 2022. When Was the Great Wall of China Built? Over 2,300 Years in 9+ Dynasties. China Highlights. Available at: https://www.chinahighlights.com/greatwall/fact/building-time.htm
The Gobi desert has been like that, a barren desert, since the glaciers retreated. That section of the wall must have been pre Ice-Age construction, back when the region was lush and watery, with seas hundreds of feet higher than today. So the analysis is wrong with regard to the dating, if presented to match up with the apparently bogus theory that that section of the Wall was built post-Ice Age. But lying with science is ART of it!
Nobody gets paid to tell the truth.