Millions of ants in an area the size of a small bedroom fill the nests. Once inside the chambers, the leafcutters drop their burdens. Tiny gardening ants take over. They clean, trim and crimp edges of the leaves, smear their own secretions on them and rough up the surfaces. On these chunks of leaf, which they line up in neat rows, the ants then place bits of homegrown fungus.
Schultz and his close collaborator, Ulrich Mueller, a behavioral ecologist from the University of Texas at Austin, believe that the leafcutters’ ability to grow and harvest fungi is akin to human agriculture. They even suggest that humans have something to learn from the ants, pointing to the recent discovery that attines use antibiotics to keep diseases in check inside their fungus gardens. “Have you ever tried to keep anything in the tropics free of pests for more than a few seconds?” Schultz says. “This is an amazing achievement.” Perhaps, he suggests, a careful study of the ants will yield ways for humans to fight disease or to farm more sustainably. “These ants have a positive feedback system—50 million years of sustainable agriculture,” Schultz says.
This remarkable record seems particularly poignant here in the rain forest. During the drive north on the new, 1,000-mile highway running from Manaus to Caracas, the fish-bone pattern of development that despoils large swaths of the Amazon is evident, with new dirt logging roads fanning off in every direction. By contrast, “the leafcutters aren’t skewing things,” Schultz notes. “You could imagine lots of scenarios where the ant nests in these forests just get bigger and bigger, where they would carry this agriculture to the point where they would tip the whole system. But they don’t.”
Schultz and Mueller have returned to the Amazon to try to figure out how the first ant—the mother of all gardener ants—began growing her colony’s food. What did she look like? How did she behave? And how on earth did she manage such a momentous transformation?
Humans have been intrigued by leafcutter ants for centuries. The Popol Vuh, the ancient Mayan chronicle, celebrated their intelligence and communication skills. Charles Darwin, on first visiting Brazil’s tropical forest, was struck by their ubiquity and industriousness. “Well-beaten paths branch off in every direction, on which an army of neverfailing foragers may be seen,” he wrote in 1839.