Kite-like structures in the western Sahara Desert.

Since 2010 numerous 'kite-like structures' have been discovered in the Middle East, and more recently the Libyan Sahara. These are prehistoric megastructures, interpreted to have been gigantic traps, into which Animals could be driven by hunters. The vast nature of these structures makes them almost impossible to detect from the ground, with almost all being detected from satellite imagery. Most of these structures are in remote desert regions, and to date, very few of these have been visited or investigated by archaeologists, leaving us with little idea about their age or the people who constructed them.

In a paper published in the journal Antiquity on 31 March 2022, Olivier Barge, Laetitia Balaresque, and Jean-Loup Baudoin of the Université de Lyon, Manfred Boelke, an independent researcher from Düsseldorf in Germany, and Lison Derrien of Aix-Marseille Université, report the discovery of almost 500 new kite-like structures in satellite images of the western Sahara Desert.

The majority of these newly discovered structures are located in two concentrations, one between the Hoggar Mountains and Erg Chech, in the Acedjerad and Ahnet region of southern Algeria, and a second stretching from the area between Erg Iguidi and Erg Chech in the area that marks the triple border between Algeria, Mali, and Mauritania eastwards along the Hank escarpment further into Mauritania. These structures differ in form from the Libyan structures, but share enough similarities for Barge et al. to conclude that they are also hunting structures, and were probably built by people from the same extended community.

 

The locations of kite-like structures. Olivier Barge in Barge et al. (2022).

The kite-like structures of the western Sahara typically have two long, converging walls, with a small proportion having two additional walls between these. Four different types of structure have been recognised in the area. Typa A, are the most numerous, with 163 known examples, and simply comprise a pair of long converging walls leading to a simple cell, similar to the first-discovered kite-like structures of the Negev Desert.

 

A Type A kite-like structure in Libya. Bermerkenswelt der Archäology.

The next most numerous type of structure, Type B, are the next most numerous with 139 known examples, and are similar to Type A structures, but have two walls which converge rapidly tecoming almost parallel, often bending, forming a narrow corridor ending in a cell.

 

A Type B kite-like structure in Libya. Bermerkenswelt der Archäology.

 

Type C structures, of which 110 examples are known, are similar to Type A structures, but end in several cells in a line, usually between two and seven, but with some larger examples, rather than a single cell.

 

A Type C kite-like structure in the Adrar/Tamanrasset area of Algeria. Bermerkenswelt der Archäology.

 

Finally, and least commonly, with only 20 known examples, Type D structures resemble to others, but are open at their ends, lacking any sort of cell.

A Type D kite-like structure in Libya. Bermerkenswelt der Archäology.

Additionally, a further 60 examples have been identified which are too badly preserved, or to poorly imaged, to be assigned to any of these groups. Barge et al. also note that Type D structures tend to be the largest, followed by Type B, with Types A and C often being quite small. 

 

(A) Average length of driving lines per type; (B) Histogram of the number of cells in Type C structures. Barge et al. (2022).

Type A structures were found all across the study area, while Type B structures were concentrated in the Hank region of Mauritania and the Tripolitania region of Libya. Type C structures are known only from the Acedjerad region of southern Algeria, while type D structures are found in the Hank region of Mauritania and the Jebel al Husawinah are of Libya. Barge et al. note that kite-like structures have also been recorded from the Nama Karoo of South Africa, but that these appear to be of quite different construction.

The different types of structures had different patterns of orientation, with Type C structures tending to be orientated towards the east, and Type D structures towards the southeast, presumably to capture animals during annual migrations. Type A and B structures were typically orientated to slope direction rather than compass points, with their openings downwards. This often results in structures on opposite sides of a valley pointing away from one-another.

Without proper ground investigation, it is impossible to be certain of the purpose of these structures, however their generally morphology and similarity to the V-shaped kite structures of the Negev Desert does strongly suggest that they were Animal traps, with the cells at the ends possibly representing pits. In almost all cases, the construction of the trap used local topology to hide these cells (i.e. the trap funnelled the Animals up a slope, with the final trap over the brow of the hill).

If these structures were used for hunting, then it is unclear what species they were built to target. The western Sahara today is an area of extreme aridity, with few large Anumals to hunt, but many of the kite-like structures face towards oueds (dry river beds) or other depressions thought to have once held water, so it is possible that they were built at a time when there were reliable water-sources, and Animals exploiting them, for at least part of the year. It the case, then it would suggest that the structures were built between 5000 and 9000 years ago, the last wet optimum of the Sahara, when the area is known from other evidence to have been inhabited by nomadic Humans.

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The spread of deserts in northern China.

There is around 2 million km² of desert and semi-desert across northern China (excluding the Tibetan Plateau), which has played an important role in the development of China as a nation, and still affects the modern Chinese economy. The desert areas provide a boundary between China and the Mongolian and Siberian steppes to the north, but also occupy a large area of land which could otherwise potentially be used for agriculture, thus improving China's food security. In addition soils blown from these areas by the wind (loess) are thought to have played a major role in the formation of the rich agricultural lands of the middle and upper Yellow River region, which has historically served as China's breadbasket, but is also considered to be a major contributor to air pollution in Beijing and other northern cities that are frequently enveloped by dust storms. The climate and precipitation of these areas is controlled by the East Asian Monsoon, and therefore it would be expected that the deserts would expand during cooler, drier climatic intervals, and shrink during warmer, wetter periods.

In a paper published in the Chinese Science Bulletin on 17 June 2013, a team of scientists led by Lu HuaYu of the School of Geographic and Oceanographic Sciences  at Nanjing University, examined sedimentary deposits from across northern China, in order to estimate the extent of desert cover during the Last Glacial Maximum (~26 000-16 000 years ago), when the climate was extremely cool and arid, and the Holocene Optimum (~9000-5000 years ago), when the climate was warmer and wetter than it is now.

The extent of deserts across modern north China. Lu et al. (2013).

Lu et al. found that different areas of desert across northern China covered between 10 and 270% more land during the Last Glacial Maximum compared to day, but that they more-or-less disappeared during the Holocene Optimum. This would seem to suggest that the deserts do indeed expand during cooler, drier periods and contract during warmer drier ones, potentially good news for China, which, like other countries, faces an unclear climatic future due to global warming, which is likely to result in a warmer, wetter climate.

The extend of deserts across north China during the Last Glacial Maximum and Holocene Optimum climatic intervals. Lu et al. (2013).

However Lu et al. sound a note of caution on these findings. The modern climate is far closer to that of the Holocene Optimum than it is to that of the Last Glacial Maximum, yet the extent of desert coverage in northern China is far closer to that during the Last Glacial Maximum than it was during the Holocene Optimum. This suggests that either there is something very wrong with our understanding of the relationship between climate and desertification, or that there must be another factor at play.

Lu et al. suggest that the most likely explanation for this discrepancy is the spread of agriculture across northern China, which is currently believed to have begun between 4000 and 5000 years ago, and that the modern deserts may be as much a product of soil damage due to poor agricultural techniques as it is due to climate change (this will affect rainfall, as ground vegetation cover affects precipitation, so removing the plants can result in less rain just as removing the rain results in less plants). This being the case it is by no means certain that the climate becoming warmer and wetter will result in shrinkage of deserts in northern China, rather it is possible that expanding and inappropriate agriculture in the area could lead to expanding deserts even as the temperatures rise.

See also Toolmaking in the northeastern Thar Desert 95 600 years ago, How fencing the Tibetan prairies is effecting the endangered Przewalski’s Gazelle, Eight people killed by landslide in Shanxi Province, China, At least nine dead following landslide in Gansu Province, northwest China and Pollen from potshards, and what it can tell us about the ancient climate of northwest China.

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