One of the Namib’s many curious natural phenomena is that of “fairy circles”: from the air they appear like a giant polka-dot pattern across a vast sheet of scorched cloth, along the eastern fringes of the desert. A closer inspection reveals discs of bare earth, fringed with lush grasses, which are higher and healthier than the ones between the circles. Measuring between 2–20m in diameter, the larger circles have an average lifespan of between forty to sixty years, as they appear, mature – growing in some cases – and then fade.

To the Himba, they are simply the footprints of their deity, Mukuru; scientists, needless to say, have been looking for other explanations, though have so far failed to solve the puzzle. Over the years, many theories have been put forward – from ostriches taking dust baths, to poisonous underground gases, rival toxic plants, not to mention the inevitable intervention by aliens – but most ideas have eventually been dismissed. The two most persistent explanations relate to sand termites and grasses competing for scarce natural resources. For a long time the sand-termite theory held sway, the notion that these busy subterranean insects were eating the roots of grasses and therefore killing them; with no remaining plants to suck up the water, it pools below the surface, allowing the termites to survive the dry season and the grasses on the periphery to thrive. But critics point out that, while termite presence is generally high in fairy circles, termites have not been found in all the circles. Moreover, the theory would not seem to explain the regular, almost honeycomb-like spacing of these circles, so clear from aerial surveys, nor the fact that these apparent carpets of bronze coins only occur in a very limited geographical range, in the arid transitional zones between grasslands and true desert.

What really threw the termite theory up into the air was the relatively recent realization among experts that fairy circles, which for years were thought to be unique to Namibia, also exist in the outback of western Australia, in similarly arid conditions, but without the number of termites. This would seem to lend greater weight to the notion of grasses in arid conditions “organizing” themselves to maximize scarce water and nutrients. While an even carpet of plants would be unsustainable in such conditions, the argument is that hardier grasses survive, sucking up the water, leaving their neighbours to die; the gap between the vegetation widens and the barren circle of sandy soil is then too hard to take seed, but rather acts as a repository for any moisture, like an oasis, which further nourishes the stronger and healthier plantlife encircling the bare earth. Further evidence that supports this reasoning lies in the fact that the circles seem to grow after dry years and shrink after wet ones. Self-organization theory – thanks to maths and computer modelling – has been shown to have explanatory potential for other natural phenomena, such as rock crystal growth, or birds’ flocking movements, in which a seemingly unstructured and chaotic group can transform itself into an organized system without any centralized control. The bottom line, however, is that, while this might seem the most plausible theory at the moment, the mystery is far from being unequivocally solved.

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