This mound has been home to termites for millennia, raising countless generations of these incredibly social and complex insects.
We humans like to pat ourselves on the back for building giant monuments that have withstood the tests of time. The Great Pyramid of Giza, for instance, towered over other man-made structures for about 4 millennia until modern engineering came along.
But we’re not the only engineers on this planet. The woodlands and plains of Africa are dotted with colossal, alien-like fortresses of hardened dirt whose origins are decidedly non-human. Who is responsible for this architecture?
Enter the lowly termite.
The oldest termite mound ever dated can be found in the Miombo woodlands of the Democratic Republic of Congo. The foundations of this 20-foot structure were first laid down 2,200 years ago, according to recent analysis of soil samples. Considering that termites generally measure about half an inch long, this architectural feat is comparable to humans building a 3,500-foot-tall skyscraper—which we haven’t yet accomplished, by the way.
Such massive mounds can be found all over Africa, but this study reveals that they may inhabit the same mound for thousands of years, slowly building up the layers. It’s hard to imagine such tiny, short-lived creatures inhabiting structures older than our houses, but the soil doesn’t lie.
Researchers from Ghent University in Belgium and the University of Lubumbashi in the Democratic Republic of Congo used carbon-14 dating to approximate the age of two active and two abandoned termite mounds. This method of dating involves measuring the amounts of different “isotopes” or forms of carbon present in a soil sample. Comparing the ratio of radioactive carbon-14 to the more common carbon-12 can indicate the age of the soil, and when the termites incorporated it into the mound.
The results indicate that the largest mound, over 20 feet tall, was first constructed between 2,335 to 2,119 years before present. Although it is now abandoned, the scientists were able to determine that the mound had seen regular use in the 12th to 15th centuries.
Even the two active mounds that were sampled in this study proved to be centuries old, with the larger one sitting atop a base built by termites 700 years ago. Today only the upper parts of the active mounds still house termites—to be exact, Macrotermes falciger, a species common to the region.
Like ants, termites live in colonies that can number up to millions of individuals. They divide themselves into castes including workers, soldiers, reproductive units, and sometimes more than one egg-laying queen. The queen normally lives 20 years, at most, meaning that these mounds might be considered ancient seats of royal termite power, handed down through myriad dynasties. Even if a colony abandons the mound, at some future point it may be rediscovered and reclaimed, as indicated by the history of the older mound.
It makes sense to take advantage of labor already completed by predecessors. According to the studies of termite enthusiast and SUNY professor J. Scott Turner, an average-sized colony containing perhaps 33 pounds of termite mass will move about 550 pounds of soil and several tons of water per year. It’s back-breaking work, but crucial for the colony; the mound not only provides shelter, but acts as a ventilation structure for its inhabitants. It may look solid, but the walls are extremely porous and allow for gas exchange with the outside air.
Termites themselves comprise a vital part of the ecosystem. Just by diligently going about their daily lives, they form high-quality soil, recycle nutrients, and clear away woody litter that would otherwise contribute to bush fires. Should the original architects leave their creations, the mounds remain ecologically relevant by providing habitats for plants and animals, particularly on African plains that experience frequent flooding.
The mounds examined in this study have served the Miombo landscape for centuries, as either basecamps for sprawling termite civilizations or hostels for other animal squatters. They will continue to stand as testaments to the large-scale, lasting achievements of such tiny creatures.