In the arid grasslands of Southern Africa, a mysterious feature dots the landscape. Circular patches of bare earth pock regions in Namibia, Angola and South Africa. Sometimes, taller grasses ring the bare patches, which can be anywhere from 7 to 49 feet in diameter. Humans have known about them for centuries: the BBC reports that the local bushmen, the Himba, tell stories about the circles—that they're footprints of the gods or that a dragon living underground has scorched the vegetation away on the earth above. But no one knows what causes them. Researchers call them fairy circles.
Many ideas as to the circles’ cause have been floating. Termites munching plant roots, fungus, poisoning from toxic native plants, contamination from radiation and even dust-bathing ostriches have all been blamed at one point and then exonerated. In an effort to get down to the cause, researchers are simply attempting to describe the patterns.
One such effort uncovered an odd comparison: The fairy rings form patterns that are eerily similar to the growth patterns of skin cells. Researchers at Japan’s Okinawa Institute of Science and Technology recently found the similarity. "It's a completely amazing, strange match," says Robert Sinclair, who heads the Mathematical Biology Unit at OIST, in a press statement.
Now, this doesn’t mean that we’ve discovered the skin of some giant creature slumbering beneath the earth. It simply suggests that there is some kind of competition for space going on between the circles that is similar to that of skin cells. The statement explains the findings, published in Ecological Complexity, in more detail:
They took satellite images of fairy circles, and a computer drew lines halfway between each pair of circles to designate invisible boundaries, much like cell walls. The computer then counted how many neighbors surround each fairy circle. Other researchers had calculated skin cell neighbors several years ago.
The results were almost identical. Both the majority of fairy circles and majority of cells have six neighbors. But the similarity gets even more specific -- the percentage of fairy circles with four, five, six, seven, eight and nine neighbors is essentially the same as the skin cells.
“I didn’t expect it to be so close,” Sinclair said. “We spent a lot of time checking because it really looked too close to believe.”
Other evidence seems to suggest that the fairy circles involve some kind of growth process, perhaps biological — they are round, start off small and grow larger.
Besides noting a strange comparison for the pattern, the OIST researchers have a more practical application for their findings. They write that their work shows that mathematical analyses and patterns used to describe microscopic world can also apply to the macroscopic world. In the future, such information could be used to look at the surfaces of other worlds and deduce whether geological or biological processes are etching patterns in the surface of planets.
The new work may have added a clue to discovering what causes fairy circles, but it appears it will be some time before we can tell for sure. Only one thing is reasonably certain: They are not caused by pixies or elves of any sort, despite the moniker we’ve given them.