The Omnivore's Dilemma - Michael Pollan [146]
Among the more specialized eaters, natural selection takes care of the whole problem of food selection, hardwiring the monarch butterfly, say, to regard the milkweed as food and everything else in nature as not food. No thought or emotion need go into deciding whether to eat any given thing. This approach works for the monarch because its digestion can wring everything it needs for its survival from milkweed leaves (including a toxin that makes the butterfly itself unappetizing to birds). But rats and humans require a wider range of nutrients and so must eat a wider range of foods, some of them questionable. Whenever they encounter a potential new food they find themselves torn between two conflicting emotions unknown to the specialist eater, each with its own biological rationale: neophobia, a sensible fear of ingesting anything new, and neophilia, a risky but necessary openness to new tastes.
Rozin found that the rat minimizes the risk of the new by treating its digestive tract as a kind of laboratory. It nibbles a very little bit of the new food (assuming it is food) and then waits to see what happens. The animal evidently has a good enough grasp of causality (“delayed learning,” as the social scientists call it) to link a stomachache in the present to something it ingested a half hour before, and a good enough memory to store that finding as a lifelong aversion to that particular substance. (This is what makes poisoning rats so difficult.) I might have used the same strategy to test my chanterelle, eating a tiny bite of it and waiting to see what happened.
Rozin’s early work on food selection behavior postulated that the “omnivoral problem” would explain a great deal, not only about how and what we eat, but who we are as a species, and subsequent research by him and others, in anthropology as well as psychology, has done much to confirm his hunch. The concept of the omnivore’s dilemma helps unlock not only simple food-selection behaviors in animals, but much more complex “biocultural” adaptations in primates (humans included) as well as a wide range of otherwise baffling cultural practices in humans, the species for whom, as Claude Lévi-Strauss famously said, food must be “not only good to eat, but also good to think.”
The omnivore’s dilemma is replayed every time we decide whether or not to ingest a wild mushroom, but it also figures in our less primordial encounters with the putatively edible: when we’re deliberating the nutritional claims on the boxes in the cereal aisle; when we’re settling on a weight-loss regimen (low fat or low carb?); or deciding whether to sample McDonald’s’ newly reformulated chicken nugget; or weighing the costs and benefits of buying the organic strawberries over the conventional ones; or choosing to observe (or flout) kosher or halal rules; or determining whether or not it is ethically defensible to eat meat—that is, whether meat, or any other of these things, is not only good to eat, but good to think as well.
2. HOMO OMNIVOROUS
The fact that we humans are indeed omnivorous is deeply inscribed in our bodies, which natural selection has equipped to handle a remarkably wide-ranging diet. Our teeth are omnicompetent—designed for tearing animal flesh as well as grinding plants. So are our jaws, which we can move in the manner of a carnivore, a rodent, or an herbivore, depending on the dish. Our stomachs produce an enzyme specifically designed to break down elastin, a type of protein found in meat and nowhere else. Our metabolism requires specific chemical compounds that, in nature, can be gotten only from plants (like vitamin C) and others that can be gotten only from animals (like vitamin B-12). More than just the spice of human life, variety for us appears to be a biological necessity.
By comparison, nature’s specialists can get everything they need from a small number of foods and, very often, a highly specialized digestive system, freeing them from the need to devote a lot of brainpower to the challenges of omnivorousness. The ruminant, for example, specializes