What the Nose Knows - Avery Gilbert [45]
Because smell and taste are inextricably linked in flavor perception, experience in one modality can affect the other. For example, some odors are commonly described in terms of taste: honey smells “sweet” and vinegar smells “sour.” The Australian psychologist R. J. Stevenson and others have shown that odors acquire taste qualities through associative learning. After a novel odor is paired a few times with the sweet taste of sucrose, the odor is perceived as smelling sweet. If paired with citric acid, it seems to smell sour. This cross-sensory link works in the other direction as well: smells can alter tastes. Strawberry odor, for example makes a weak sugar solution taste sweeter, and a whiff of soy sauce boosts the perceived saltiness of a saline solution. Sensory researchers have just begun to understand the psychological interplay between smell and taste. They are now looking at how these senses are neurologically cross-wired in the brain. To a smell-centric guy like me, the study of taste is about to become much more interesting.
The Pleistocene Barbecue
Carnivores rarely savor their food: they rip, chomp, and swallow. Herbivores chew for hours on end, not for sensory pleasure but to make tough, fibrous plant matter digestible. Humans, in contrast, anticipate, savor, and linger over the aroma of food. We go to great lengths to increase the appeal of food by cooking it and adding spices. The second way of smelling not only provides the pleasure we take in eating, but also may be the key to how the human sense of smell has evolved over time.
Traditionally, researchers in cultural anthropology and sociology have treated food preparation as an expression of culture, as a collection of behaviors driven by custom and creativity only. A new generation of behaviorally oriented evolutionists is now challenging this profoundly unbiological point of view. The Harvard University anthropologist Richard Wrangham, for example, sees cooking not as an optional behavior—a cultural frill—but as a biological requirement for human survival. Surveying the evidence, he finds that “no human populations are known to have lived without regular access to cooked food.” Even the Inuit hunters of the Arctic, famous for their raw diet, occasionally cooked their whale blubber.
Hominids—the near-human species that link us to our common ancestor with the chimps—were definitely cooking with fire 250,000 years ago. Wrangham finds evidence of cooking as far back as 790,000 years, and speculates that it may have begun as far back as 1.7 million years ago. In any case, cooking with fire was well established when our first anatomically modern ancestors emerged in Africa some 100,000 years ago. We’ve grilled a lot of mastodon steaks through the ages.
The invention of cooking had profound consequences for diet and social behavior. Cooking releases nutrients and makes vegetables faster to eat and easier to digest. Wrangham calculates that for a 120-pound woman to take in 2,000 calories a day, she would have to eat eleven pounds of raw fruits and vegetables. That’s a lot of time at the salad bar. Clinical studies show that raw-food cultists in Germany struggle to keep up nutritionally with their countrymen: they suffer from chronic energy deficiency and the women fail to menstruate. If European sophisticates with desk jobs and handy supermarkets can’t thrive on a raw-vegetable diet, how well would a band of hunter-gatherers