Tasty (5 page)

Given the limited archaeological evidence of cooking fires more than one million years old, this theory is controversial. (Wrangham points out that evidence of fire use tends to disappear over time.) It also doesn't account for a second burst
of brain growth after one million years ago, leading up to
Homo sapiens
, that has convinced many anthropologists that early humans began to cook later. But if the theory is true, a cooked diet had a large hand in our evolutionary success and anatomy.

• • •

As brains grew, natural selection redesigned the entire human head, including the interior of the mouth and nasal cavity. Smell returned in a new guise. In most mammals, a bone called the lamina transverse divides the nasal cavity. Chewing food liberates aromas in the back of the mouth, but this bone keeps them from reaching the nose, allowing animals to focus on smells around them. As apes evolved, the lamina transverse disappeared. Then, in humans, the passage from the mouth up into the nasal cavity shrank. It was merely a few centimeters' difference, but it supercharged our ancestors' capacity to experience flavor. As people chewed, a cascade of aromas reached olfactory receptors via this back passage.

Smells had tightly knotted our ancient ancestors' expanding awareness to the world around them. This anatomical legacy is still with us. As it was in the earliest mammals, the human olfactory bulb remains just a single synapse removed from the neocortex, where sensations become perceptions. This isn't true of the other senses; taste signals pass through the brain stem and hypothalamus before they reach the neocortex. Smells are unfiltered, immediate. As they entwined themselves with taste and the other senses during meals, flavor came alive.

• • •

At the Gesher Benot Ya'aqov site, people likely gathered for meals, savoring cooked fish and deer meat dripping with bubbling fat and the crackle of seared skin. They ate, drank, talked, and rested, satisfied. They'd reached the last link in a long chain of cooperation—planning, gathering, hunting, butchering, preparation—and the reward, a feast and fellowship.

In his second book on evolution,
The Descent of Man
, Darwin linked the rapid expansion of human intelligence to man's social nature: our talent for communicating, and for living and working together as a unit. The hardships our human ancestors faced likely pulled them together into tight-knit groups. A group of chimps in southeastern Senegal that Jill Pruetz studies follows this dynamic. Most chimps live in woodlands. But this area is mostly savanna, and food is sometimes sparse—conditions that have forced the Fongoli chimps, nicknamed for a stream in their habitat, to work more cooperatively. They form a larger, more cohesive group than typical woodland chimps, and are more willing to share food; in one encounter Pruetz observed, dominant males declined to challenge a hungry female who wanted to take fruit from a pile they'd made. They also fashion basic tools: sticks to scoop termites out of mounds, and spears to skewer tiny creatures known as bush babies that slumber in the nooks of tree branches. This yields a few ounces of meat.

One might expect to find that animals belonging to larger groups, with more complex dynamics, had larger brains. In the 1990s, the California Institute of Technology's John Allman set out to investigate this theory among primates. He was surprised to find that primates with bigger brains relative to body size
didn't
form larger social groups. But when Robin Dunbar of Oxford University narrowed the question down, he found something surprising. Overall brain size
might not vary with group size, but the size of the neocortex did. Humans have the largest neocortex relative to body size of any animal; it's what gives the cathedral of flavor its magnificent architecture. It braids the basic urges and sensations around food together with thoughts, memories, feelings, and language. And it helps tie groups, and society, together.

Early humans had to collaborate to survive, developing complicated strategies to thwart adversity. Making tools and controlling fire require not only technical skill but knowledge that must be preserved and passed on to others. Hunting demands planning and teamwork. And as all backyard grill masters know, cooking meat depends on the skilled butchering of animal carcasses, fire management, and a dash of creativity. Over time, cooking became about more than just filling stomachs. Humans developed codes and customs around food. Using tools and knowledge to create flavor was the earliest spark of culture.

Every successful species adapts to its environment. Rick Potts, a paleoanthropologist who directs the Smithsonian Institution's Human Origins Program, says that humanity's talent was more formidable still: our ancestors adapted not just to different environments but to the hard reality that those environments are always changing.

This is one explanation for the great diversity of flavors and cuisines in the world today, and for a certain plasticity in human flavor sense that other animals lack: why we so easily develop a liking for things that are intrinsically unpleasant, such as bitter coffee or beer, or the heat of chili peppers or wasabi. The chaotic landscape of ancient Africa wasn't just savannas and scrub: it was dotted with volcanoes, rivers and lakes, plains and peaks, from more than 500 feet below sea level at Lake Assal in the Afar depression, the lowest point in
Africa, to 19,340 feet above sea level at Mount Kilimanjaro, the highest. Moving about these changing habitats was how humans first learned to live and thrive almost anywhere. Surviving the East African Rift's challenges was just the warm-up for the big show of world domination.

CHAPTER 3

The Bitter Gene

O
ne day in March 1990, President George H. W. Bush banned broccoli from Air Force One. Broccoli belongs to the genus
Brassica
, the plant family that includes mustard, cabbage, and brussels sprouts, most of which have a similar defense: when cut, their cell walls break, triggering a chemical reaction that releases waves of alkaloids, complex molecules that the human body reacts to in many ways. The most obvious is their bitter taste.

When the news broke, nutritionists questioned whether this decision set a bad example for America's children. Incensed California farmers dispatched a cross-country truck caravan bearing ten tons of fresh-cut broccoli stalks to Washington. “I don't think the president was given broccoli when it was properly cooked,” Julia Child weighed in. “Broccoli has to be peeled.” At a state dinner, Bush was overheard jokingly complaining about the ruckus to the Polish prime minister. “The broccoli growers of America are up in arms against me,” he said. “Just as Poland had a rebellion against totalitarianism, I am rebelling against broccoli.”

Pressed for an explanation at a press conference, Bush made a now famous denunciation: “I do not like broccoli, and I haven't liked it since I was a little kid and my mother made
me eat it. And I'm president of the United States, and I'm not going to eat any more broccoli!

“There are truckloads of broccoli at this very minute descending on Washington. My family is divided. For the broccoli vote out there: Barbara loves broccoli. She has tried to make me eat it. She eats it all the time herself.”

“Cauliflower? Lima beans? Brussels sprouts?” shouted members of the press corps. Bush gave another thumbs-down to brussels sprouts.

George W. Bush shared his father's distaste. On his first trip abroad as president in 2001, he visited his Mexican counterpart Vicente Fox, a broccoli farmer. When his motorcade arrived at Fox's ranch in the low rolling hills of Guanajuato state, Bush got out and found himself standing against the backdrop of a vast field of broccoli stalks. The tangy scent of the cruciferous vegetable enveloped everything. Reporters asked him to comment. He hesitated for a second, then flashed a thumbs-down. “Make it cauliflower,” he said.

Barbara Bush liked broccoli; her husband and son did not. Such stark differences are a basic feature of the sense of taste. Taste perceptions are genetic, programmed by DNA, traits passed down over millions of years that boosted the odds of survival in our evolutionary past. While both environment and life experience play a role in taste and flavor, the variety in human DNA is one of the main reasons why, like snowflakes, no two flavor senses are the same.

The great range in human taste perception makes it unique among the senses. The sensitivities of vision, hearing, touch, and smell vary only modestly from person to person. To survive, after all, our ancestors needed to live in more or less the same sensory world. Fragile, warm-blooded bodies function only within certain thresholds of heat and cold, so
humans have similar tolerances for those. The rods and cones of our retinas tend to detect the same color wavelengths and play of light and shadow. The cochlea, the snail-shell-shaped organ in the inner ear, picks up common levels of noise and a range of pitch. And the olfactory epithelium in our noses discerns a similar array of incoming smells.

But the sense of taste is a sentinel, chemically testing everything that enters the mouth, so it has been molded by everything our ancestors ate and drank over the eons. It never occupied a single sensory world, but many. This is especially true of the taste we call bitter.

Bitterness originated as a biological warning system to keep toxins out of the body. Jellyfish, fruit flies, and even bacteria can sense bitter compounds, indicating this basic aversion can be traced back to the dawn of multicellular life. Sea anemones, for instance, which first appeared 500 million years ago, can sense and vomit up bitter substances that enter their digestive tracts. More recently, this taste has evolved in animals in tandem with plants, which produce most of the world's bitter substances. Plants developed toxic defenses to kill infectious microbes and to protect themselves from being eaten. There are many thousands of plants, and bitter compounds are seemingly uncountable. Our taste for bitterness is a product of this diversity—and of the boldness of our ancestors, who, after departing Africa a hundred thousand years ago, lived in and sampled the plant life of every habitat on earth.

A bitter substance on the tongue triggers an electrochemical cascade in the brain, which produces distaste. The outward result is a distinctive frown: mouth turned down, nose scrunched, tongue jutting out, as if to expel the unwanted substance. Faces across the animal kingdom, from lemmings to lemurs, display variations of this grimace.

Yet humans have a love-hate relationship with bitterness that runs through all cuisine. The word “bitter” comes from the Indo-European root “bheid,” meaning “to split,” the same root as “bite.” In the Bible, bitterness is a metaphor for the suffering of the Jews. The bitter herbs used in the Passover seder,
maror
in Hebrew—horseradish, and parsley or endive dipped in salt water—recall the pain of bondage in Egypt.

But bitterness tastes good (for those who tolerate it well) when combined with other flavors. If it disappeared, a spark would vanish from food. Broccoli and its relatives from the mustard family, including cauliflower, brussels sprouts, kale, and radishes, are the most cultivated vegetables on earth. In the South, collard greens are often braised with pork; the fat and rich flavors of the meat soften the bitter flavor of the greens, and the bitterness gives the smoothness a tang. Chocolatiers have spent the five hundred years since Hernán Cortés, the conqueror of the Aztec empire, brought cacao beans to Spain from Mexico tempering their natural bitterness with sugar and milk. An element of bitterness is essential to beer and pickles—and coffee.

To make coffee taste good, the ancient, implacable force of bitterness is first summoned, then brought to heel. To understand how this process works, I visited the headquarters of Gimme! Coffee, a small chain of cafés and roasteries based in Ithaca, New York. The Gimme! roastery sits in a converted farmhouse on the edge of town. Inside, Jacob Landrau was monitoring two gas-fired Probat drum roasters, vintage black contraptions made from hand-cast steel parts. Each consists of a steel drum rotating inside a frame, like a clothes dryer, heated with gas jets to temperatures between 200 and 400 degrees Fahrenheit over the course of a roast, which takes about ten minutes. During the summer, temperatures can top 100
degrees in the roasting room, which lacks climate ­controls—that's a luxury reserved for the coffee beans, which are stored in an adjacent room where heat and humidity levels are kept constant.

Raw, dried coffee beans are a pale green; they are seeds that have been removed from a reddish fruit, then soaked and cured. When chewed, they have a mealy consistency and a grassy taste that's not particularly bitter. Many substances contribute to coffee's bitter taste; the best-known is caffeine. But roasting itself is responsible for most of it, teasing out chlorogenic acid lactones, which break down to form phenylindanes as the beans turn dark brown in the final stages, making darker roasts more bitter.

Landrau uses a laptop to track the temperature inside the roaster, but his own senses also guide him. If there's too much heat, the beans desiccate; not enough, and they turn bitter too quickly. He follows the sound of the beans as they rattle around in the drum, their appearance, and their aroma, all of which change minute to minute. Each batch has its own character, based on the type and age of beans used, as well as subtle factors such as the atmospheric pressure, quirks in the roasters, and the time of day. All must be managed to trigger a particular set of chemical reactions that generate the perfect flavor. If there's not enough bitterness, the coffee is lifeless; too much, and it's undrinkable, like the day-old pot at the back of a 7-Eleven.

On the day I visited, Landrau walked me through a roast from start to finish. After nine minutes in the roaster, the shells of the beans began to break, making a popping sound against the drum. This is called the first crack. Sometimes there are two or three cracks, if you apply enough heat: that means more bitterness. Landrau turned the heat off for a
moment before turning it back up. This began a new roasting phase, in which sugars break down into water, carbon dioxide, fatty acids, and an assortment of flavor compounds. The temperature peaked at 389.9 degrees. “If you continue to develop the sugars and just burn it, that's the secondary spot where you're going to get the bitterness again,” he said. He must also watch for tipping, another warning sign for excessive bitterness, when black spots appear at either end of the beans.

Landrau shut off the flame and opened the drum. The beans, now a robust-looking medium brown, poured into a circular tray, where rotating blades pushed them around to allow them to cool evenly.

Later that day, Liz Clark, who trains baristas for Gimme! shops, drew a graph showing lines for three tastes—sour, sweet, and bitter—rising and falling over time. We were in the Gimme! lab, where new formulas and techniques are tested. The graph is an important guide for baristas, illustrating something called “the rule of thirds.” Because different substances dissolve at different rates, a single shot of espresso contains many flavors that emerge at different times as purified water passes through ground, roasted beans. Baristas must gauge the fineness of the grind, the water pressure, and the changing form of the drip as it emerges from the bottom of the filter and falls into the cup.

Clark asked a barista to tamp some finely ground espresso powder into a filter basket. It was a blend called Leftist (“Rich chocolate, caramel apple. Baking spice finish,” its ad copy said). The barista inserted the basket into the espresso machine and gingerly pulled the lever, forcing 200-degree water through the grounds at nine times atmospheric pressure. As the shot dripped out, she divided it into three cups.

The first was dark brown, syrupy, and intensely sour. The
second was thinner and reddish, with a slight sweetness. The last was a pale, sandy color; “blonding” is a sign the shot has reached its endpoint. It was bitter. Individually, each cup tasted terrible, the bitter one most of all. Yet when the three were combined, the flavors played off each other delicately. This process can easily go awry: espresso machines are very sensitive, the flavors they produce temperamental. “You can really get to know someone's personality by the way they pull the shot,” Clark said. “Even though there is what could be seen as a very narrow set of parameters, there is an almost infinite amount of variation for finding delicious shots in there.”

• • •

Decoding the exact meaning of this ancient signal, alive in our bodies and food, is one of the more vexing problems in human biology. It has challenged scientists ever since one day in 1930, when two chemists in a factory had a fateful argument.

They were tinkering with formulas for blue dye at the DuPont chemical company's Jackson Laboratory at Deepwater Point, New Jersey. Arthur L. Fox was pouring a container of a white powder, a substance called phenylthiocarbamide (PTC), into a bottle when he fumbled, sending a fine puff into the air. His colleague, Carl Noller, a visiting Stanford professor, was standing nearby and inhaled some. It traveled from his nose into the back of his mouth and onto his tongue. It tasted sharply bitter. Fox was surprised; he had also inhaled some powder, but tasted nothing.

Fox put a pinch of PTC on his tongue and assured Noller it was tasteless. Noller dipped his fingers into the powder and stuck them into his mouth and winced. They asked other lab
workers to do the same. A spontaneous experiment unfolded, with the scientists and technicians acting as their own guinea pigs. The mysterious split in reactions was confirmed: some could taste it, others could not.

In 1930, scientists believed that people's tastes were essentially the same. When they differed, it was attributed to mood or temperament. A child's dislike of brussels sprouts was a matter of poor discipline, not biology. The PTC discovery shattered that conventional wisdom. “Tastes differ far more than anyone realizes,” Fox told an interviewer. “Beets may actually be disagreeable to Mary, while Johnny loves them. Father may not be able to tolerate buttermilk, and Mother may find garlic revolting. These foods simply do not taste the same to them as they do to others.”

Fox's accidental discovery had pulled back a veil over the inner workings of genes. In Fox's time, scientists knew that the human body had a blueprint made up of genes. But lacking knowledge of DNA, they had no idea what that plan looked like. Every feature of human biology had to be connected to genes in one way or another, but it was impossible to disentangle their influence from other biological forces such as environment, upbringing, and aging. Fox's discovery, a simple genetic trait easily identified by a taste test, was the stuff of scientific revolutions. It might reveal how genes evolved and how they responded to changing climates or habitats. It could expose unknown genetic differences between genders, cultures, and races.

The Augustine friar and botanist Gregor Mendel first stumbled upon such single-trait genes—and with them, the first basic understanding of genetics—in the mid-nineteenth century, when he tried to breed pea plants to produce violet-­colored flowers. Working at the Abbey of Saint Thomas in
Brno, in what is now the Czech Republic, Mendel crossed white-bloomed peas with purple-bloomed peas. Instead of violet, only purple blossoms appeared. He then bred thousands of pea plants and studied the resulting colors. Purple blooms crossed with purple or white yielded purple flowers. Only when white was bred with white did white flowers grow. He never did get violet.

The colors, he guessed, were produced by basic units of heredity, one from each parent. Mendel called them “factors.” Purple factors were dominant. This allowed him to statistically predict the prevalence of each color: of every four blooms, three would be purple, one white.