The Viral Storm by Nathan Wolfe Page B

habitat were spread out, which again forced seasonal movement. Wild environments, with a few minor exceptions, 2 lacked the capacity to sustain large populations of people. As a consequence, human population sizes were small, probably numbering no more than fifty to a hundred people in a group, and mobile.

    Human population through history. ( Dusty Deyo )
    As domestication truly kicked in around five to ten thousand years ago, this would all change. With a combination of domesticated plants and animals, humans gained the capacity to have sustained sources of calories year-round. Agriculture (i.e., the domestication of plants) made it possible for human populations to stay in one place and avoid the constant movement that characterizes hunting-and-gathering populations as well as populations with only domesticated animals, which need to move in order to find feed for their herds. A sedentary lifestyle and the capacity for food surplus radically increased the potential for populations to grow, leading to the first real towns and cities. The particular combination of larger population sizes, sedentary groups of humans, and the growing populations of domestic animals would play a central role in transforming the relationship between humans and microbes. But humans aren’t the only animals that tame the wild.
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    Despite conventional wisdom, the capacity for domestication is not unique to humans. The most striking example of domestication in the animal kingdom comes not from primates, dolphins, or elephants—in fact, not from a vertebrate species of any type—but from ants. Far from simple-minded insects, ants are part of unique and complex colonies, each of which is perhaps better imagined not as a group of individual ants but rather as a collective ant “superorganism.” 3
    Leaf-cutter ant colonies exist in most tropical American habitats. Known to schoolchildren worldwide for their incredible strength, the workers march through the jungle carrying pieces of green leaves many times their own size back to the nest. Yet the leaf-cutter’s strength is not its most interesting feature. This amazing group of ants has mastered the art of domestication. Rather than eat those massive leaves, the workers chew them up into a fertilizer. The colony uses the fertilizer in order to support their gardens—for leaf-cutter ants, made up of the Atta and Acromyrmex groups, cultivate a fungus-based crop and have spent millions of years living off it. These ants are farmers.

    Leafcutter ants in a fungus garden, Belize. ( Mark Moffett / Getty Images )
    Domestication of fungus has helped leaf-cutter ants become one of the most successful species on our planet. Mature leaf-cutter colonies, measuring fifteen meters across and five meters deep, can house upward of eight million ants. The massive underground colonies are sedentary, sometimes lasting for more than twenty years in the same location.
    These remarkable ants have attracted a number of scientists, including a Canadian researcher named Cameron Currie. Dr. Currie has used molecular tools to examine the genetics of the ants, their fungus, and the other members of this incredible community. His research has shown the evolutionary links between the ants and their fungus crop. The colonies and their crop species have lived together for tens of millions of years, a much more mature farmer-crop relationship than that seen in humans.
    Like human farmers, the ants have agricultural pests, including a specialized fungal parasite that spoils the farms. Dr. Currie has shown that not only have the ants and their crops lived together for millennia; the parasitic fungus has been along for the ride since the beginning. Another amazing twist to this elegant system is that, like human farmers, the ants utilize a pesticide. They cultivate a species of bacteria that produces fungicidal chemicals that help the ants control their vermin. Some people think of ants as pests, but these ants have