Dark earth, the strange patches of black soil rich in nutrients that cause plants to grow at accelerated rates, while also capturing unusually high amounts of carbon from the air, is one of the Amazon rainforest’s greatest mysteries. Since these patches of dark earth were first discovered by European colonizers in the 1880s, debate has raged over their origins, with ideas ranging from the natural to the artificial. Variants of this dark, nutrient-rich soil have been found in a range of locations around the world, and are most often associated with the accumulation of materials in soil after long periods...