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By Root 616 0

leafcutter’s fungus could first have arrived at ant nests by happenstance—as spores carried by the wind, for example. If it found its way onto the body or food of a browsing worker, all the better: it would likely end up in the oral pocket all ants use to hold the detritus they clean off each other or strain from a meal before ingestion. About once a day ant workers spit a pellet from this pocket onto the midden pile, like a cat spitting out a fur ball. These pellets include potentially edible trifles, bits of fungi among them.3 Then, as with the fruiting plants in early human camps, the fungus may have begun to grow from excrement or castoff garbage near where they live.

Or maybe the ants began their relationship with fungi by eating mold sprouting on palatable but overripe food, in much the way Middle Eastern tribes are thought to have discovered cheese. The ancestor of fungus growers may have shared a characteristic with slovenly Malaysian Proatta ants, who will collect about anything. Lacking typical ant fastidiousness, they allow refuse to accumulate in the nest, which can resemble an insect version of a fraternity house. As happens with pizza under the sofa, the mess can get moldy.4

Sprouting from trash, excrement, or food, the fungus may initially have been a harmless interloper suited to nest environs but of no value to the ants, but any genetic change that made the fungus useful would have increased the odds of its survival among them. The camp followers could in this way have taken the first evolutionary steps in their own domestication. A fungus among ants or a plant among humans would be more successful, for example, if it were tasty, causing the ants or humans to change their behavior to nurture it. After that, its evolution would have in a sense been “domesticated.” (By applying this domestication process across species on a global scale, people have shifted the very balance of evolution on our planet such that from now on, wild organisms will either accommodate to our existence or survive only as a result of our active conservation efforts.)5

The first apples near human dwellings were nowhere near as juicy as those of today. They have been unconsciously and incrementally improved by what Darwin called artificial selection, as people reached for the best available fruit and coddled the apple trees on their farms. Ants are just as picky. Workers selected the fungi that offered the greatest nourishment and gustatory satisfaction, which encouraged them to maintain the substrate for the fungus—garbage or old food—so they could feed off its blooms of hyphae.6 And so, fifty million years ago, farming was born among the ants.

DOMESTICATION

Except for the edible tips of its microscopic hyphae, the garden fungus isn’t very different from its wild relatives. The ants are the ones that have undergone dramatic changes during their evolution as agronomists, from developing leaf-processing assembly lines to gaining the skill to remove weedy microbes on the gardens to losing the ability to digest certain proteins. To keep the fungus cultures pure, what may have once been a fraternity-style slob species has been reconfigured over time into today’s leafcutters, the ultimate neat freaks.

We suppose that in the history of humanity, the farmers controlled the domestication of plants and animals, but domestication and artificial selection, whether in humans or ants, are more often two-way processes. Each success story is a mutual accommodation, a symbiosis between parties. Domestication can turn being eaten into a good thing by providing benefits for some prey. In organisms that haven’t been domesticated, the ratio of predators to prey can shift wildly, as has been shown for the Canada lynx and the arctic hare. When there are too many hungry lynx, the hare population takes a nosedive, which then causes the lynx to die from starvation. The low number of lynx in turn gives the hares the opportunity to reproduce and replenish their population. It’s an endless, brutal cycle.7 In a domesticated partnership, in contrast, the cow