Tasty Read Free

of years. It has driven evolution, and lately human culture and society, in new directions. It is a kind of slate on which human struggles, aspirations, and failures have been written, erased, and written again. We owe our existence and our humanity to it—and, in many ways, our future depends on it, too. As science unlocked flavor’s secrets, its influence over what we eat and drink exploded. From the food labs of large corporations to the kitchens of the world’s finest restaurants to the bar down the street, science shapes surprising and sometimes alarming new sensations tied to both our DNA and our deepest drives and feelings.
    In March 1998, scientists at the National Institutes of Health (NIH) in Bethesda, Maryland, found themselves on the cusp of one of these paradigm-changing advances. They were searching for a sweet taste receptor, a kind of protein on the tongue specially tailored to snare sugar molecules out of the slurry of mashed-up food and drink in the mouth. More than two thousand years after Democritus and Alcmaeon, science was finally closing in on the mechanism of taste that enables us to transform the molecular arrangements in food into sensory perceptions and, ultimately, culinary art.
    Over the previous decade, the science of genetics had made startling advances. For the first time, scientists were decoding the entire length of human DNA, the helical, ladderlike molecules found in chromosomes in the nucleus of every cell. The total human genome is made up of three billion pairings of four amino acids; each pair forms a rung in the ladder. The variations in the pairs constitute a code that maps out the blueprint for the body and all its functions. Every person gets two of these blueprints, one from each parent. Uncoiled, the DNA in a single cell would be about six feet long; if all the DNA in the human body were laid end to end, its length would be the equivalent of seventy round-trips from Earth to the sun.
    Isolating genes—discrete segments of DNA that carry out specific biological instructions such as making proteins, the body’s basic building blocks—had enabled scientists to find and treat diseases and to better understand human evolution. Now, genetics offered a way to quantify the intangibles of flavor, to explain its bewildering diversity. The nose’s receptors for smell had been isolated and their genes decoded seven years earlier, an effort that later won a Nobel Prize. The smell receptors had been comparatively easy to find. Theywere plentiful and concentrated in the small patch of tissue on the roof of the nasal cavity; live ones can be harvested with a Q-tip.
    But the search for taste receptors had dragged on. They had proven almost impossible to isolate: Not only are there relatively few taste-­detecting cells to begin with, but it is difficult to coax a reaction from them. The body has a vast apparatus to detect all kinds of cues, from hormones on the inside to heat, cold, pressure, light, and chemicals on the outside. Most of these reactions are very sensitive. It takes only a tiny dose of adrenaline to get a rise out of the receptors that detect it. But taste receptors are about a hundred thousand times less sensitive. This is because they interface with the chaos of the world around us. Given the sheer volume and variety of sensations the tongue encounters in a single meal, the brain would overload if every molecule lit up the taste receptors. Taking a sip of Coke would be like staring into the sun.
    The NIH scientists, led by Nick Ryba, had finally leaped many of those hurdles. They were examining taste bud cells while also searching stretches of the genome, hoping to match up a taste receptor protein with the gene that created it. They harvested DNA from the taste buds of rats and mice, whose sense of taste is similar to our own. The trick was finding the right individual gene: a short, specific stretch of code tucked somewhere among vast, unmapped