Unseen City

by Nathanael Johnson

  Some hundred million years ago, leaves like this shaded dinosaurs on every continent. The ginkgo trees that grow in our towns are virtually identical to the ginkgos that began to appear two hundred million years ago. The golden age of the ginkgo family, Ginkgophyta (technically a whole division of plant life), was the Cretaceous, which lasted from 140 million to 80 million years ago.

  Evolutionarily, Ginkgophytes are between ferns and modern flowering plants. The pollen of almost every other plant is passive: It floats around, and if any grain ends up in just the right place, in just the right flower, it can deliver its payload of genes. Ginkgo pollen, by contrast, is active: Once it lands on a female plant’s seed cone, it opens up and releases sperm that swim using their thousands of filaments arranged in spirals. I find it astounding that something so stationary (a tree!) can produce a mobile creature that rides the wind out into the world and then scrambles to the finish line to spread its DNA. Imagine if evolution had scaled this up and trees made little walking body parts to carry and bury their seeds.

  Ginkgophytes thrived in a warmer, wetter time, when the poles were temperate regions and now-extinct monsters browsed among the trees. As botanist Peter Crane puts it in his book Ginkgo, “Several different kinds of ginkgolike trees watched as our ancestors transformed from reptiles to mammals.” Perhaps those scuttling ancestors chewed ginkgo fruits. Something must have given the ginkgo a reason to produce those awful smells—some Cretaceous scavenger sniffing for decaying flesh.

  The Ginkgophytes couldn’t keep up with the changing planet. The world transformed dramatically sixty-five million years ago, when an asteroid slammed into what is now the Yucatán peninsula. The debris it threw into the atmosphere blocked the sun, making Earth colder. The dinosaurs died, and so did many relatives of the ginkgo. The Oligocene was rough for ginkgos too, and they disappeared from the poles. In the Miocene, they abandoned North America, and then died out in Europe during the Pliocene. Finally, after every one of the tree’s relatives died off, only a few protected valleys in China harbored ginkgos. If we were similarly orphaned, it would mean that the planet would have lost all the creatures in which we see some flicker of commonality: all apes and monkeys, all dogs and whales and bears, all the rest of the mammals, all frogs and lizards and birds—all the creatures having a central nerve cord like our spinal cord, including many invertebrates, like sea squirts. Our closest remaining relatives would be things like starfish. If you can imagine a world in which we were the sole living representative of the phylum Chordata, then you can understand the isolation of the ginkgo.

  It’s tough for anachronisms like this to survive, because the symbiotic alliances they’ve made (such as the one oaks have made with squirrels) fall apart as their friends go extinct. But ginkgos managed to find a new friend: humans. The trees probably would have died off if people hadn’t taken a liking to them. People have been nurturing ginkgos for at least two thousand years.

  Humans carried the ginkgo out into the world, reversing its retreat. In 1730, Dutch merchants brought a ginkgo from Japan to the Botanic Garden in Utrecht, Holland. People were eager to plant this unusual tree. From there, the species traveled to England, and then, in 1784, to Philadelphia.

  It seemed there was no place for the Ginkophytes as the age of dinosaurs became the age of mammals. But now, oddly, ginkgos find themselves uniquely suited to the age of humans. They are resistant to pollution and disease, and are famously resilient in the face of urban abuses (a ginkgo less then a kilometer from ground zero survived the nuclear blast at Hiroshima, though the shrine behind it was flattened). They prosper in the sticky heat of New Orleans and the cold winters of Montreal. They prefer good soil, but can grow well in a square of dirt between concrete slabs. They thrive in partial shade, which is what you get in the presence of tall buildings. By clinging to life for millions of years, these trees have landed in an era offering a new ecological niche—the city—for which they are perfectly adapted.

  The Evolutionary Fingerprint of a Mystery Animal

  The most compelling hypothesis I’ve seen to explain the decline of the Ginkgophytes is that the trees lost their seed distributors.

  Many plants rely on partners of other species to help them reproduce: Darwin’s orchid, for example, cannot complete the sex act without the cooperation of Morgan’s sphinx moth and its twelve-inch-long tongue, which is precisely adapted to the shape of the flower. If one dies out, so will the other. Seed distributors are not quite so vital, and ginkgos can still reproduce quite well on their own. But without assistance, the trees only spread to new areas slowly. Each generation can travel only as far as a nut can roll. It takes thirty years for a ginkgo to reach sexual maturity and produce its first seed. So, about a foot per decade—far too slow to outrun glaciers. Plants often solve this problem by recruiting animals to carry their seeds.

  Surely those pungent seeds evolved for a reason, besides annoying me. Ginkgos likely coated their seeds with stinking flesh to appeal to the sorts of creatures that love vile, stinking things. Perhaps it was a dinosaur or an ancient mammal that gravitated toward the smell of rotting meat. When this mystery creature ate the seeds, it would have absorbed the fruity exterior as it passed through its digestive system, but it would have deposited the seed itself, along with a small pile of fertilizing manure, in a new location. Ginkgo seeds sprout more readily if the fruit around them is removed.

  This hypothesis is buttressed by the fact that several modern creatures eat the nuts. Botanist Peter Del Tredici, while on China’s Tianmu Mountain conducting research for his doctoral thesis on ginkgos, saw red squirrels and palm civets carrying off the seeds. Leopard cats in China eat them, and in Japan, raccoon dogs and badgers find them alluring. Here in the United States, people have seen their dogs eat them (and, more frequently, roll in them). Eastern gray squirrels eat ginkgo nuts and I have seen a fox squirrel poking around a cluster of hanging ginkgo fruits.

  That squirrel may have already eaten some of the seeds, but I didn’t see it pluck any of them. Instead, it walked out along a spindly branch that rested on the bough of a neighboring pine—at least until the squirrel weighed it down and it gave way, sending the rodent tumbling. Just as quickly, the squirrel caught a branch with a rear paw and swung like that for a moment, not showing the slightest hint of alarm.

  If the squirrel wasn’t going to claim the fruit, I decided, I would. I picked one of the seeds and took it home.

  The fruit was still green. The skin was frosted with white powder, like a Turkish delight. Beneath this was plump flesh, delicately mottled. The stem connected in a lopsided lump, like haphazardly melted wax. It didn’t smell at all. I left it on my desk.

  The Chemistry of Stench

  One morning when I was nursing a cup of coffee at my desk, attempting to catch up with the Internet, I noticed that I was grinding my teeth. Wait, I thought, and I sniffed.

  After a week, the ginkgo fruit had turned yellow, and started to collapse inward. I leaned close and inhaled, then jerked spasmodically backward. The smell was unmistakable. And though I’d thought it couldn’t possibly be as bad as I had remembered, it was just as pungent. You know that moment in a horror movie when the protagonist opens a box and finds her best friend’s corpse, along with the worms that have been eating him? The seed was the friend. I was the protagonist.

  Surely this perfume is made up of many subtle parts, but the main olfactory chemical released by the seeds is butyric acid, which is also present in rancid butter and vomit. There is also hexanoic acid, which has a fatty, waxy, barnyard kind of smell. But the combination of these two acids’ smells is not enough to describe the ginkgo fruit’s stench. It’s both of those things, plus a spritz of essential oils concentrated from a stout case of trench foot. An eighteenth-century Swedish naturalist, Carl Peter Thunberg, claimed that the Japanese ate the fleshy seed coat. I do not believe it.

  I really had to get up close to smell it. This little fruit wasn’t stinking up my whole office, it was ju
st squeezing out the occasional jet of volatile chemicals. By the time these chemicals reached my nose, about two feet away, they were diffuse enough to affect my liminal perception without triggering a conscious response—at least for a little bit. I picked it up gingerly and carried it outside.

  COOKING GINKGO

  When people do eat ginkgo seeds, they remove the stinking flesh and roast the interior nuts. After a few more weeks, I resolved to try this. The juices in the fruits contain chemicals closely related to those in poison oak and ivy, so I put on blue latex gloves. Josephine also wanted to wear gloves, though they were far too big and fell off whenever she let her hands drop below her waist. When a food is forbidden to or declared inappropriate for her, like coffee, she insists that she loves it. But her reaction to the ginkgo seed was visceral: She wrinkled her nose, squinched her eyes, and pulled away with undeniable disgust.

  In traditional production, I’d learned, people often bury the nuts until the fruit has rotted away and then dig them up again. A faster method involves immersing the seeds in water (to suppress the smell) and squeezing off the flesh by hand. I took a small bowl of water to the backyard and dropped my ginkgo seed inside. Josephine squatted beside me, intent. Most of the flesh came off with the first squeeze, and the rest was easy to rub away. The seed was a smooth tan oval, flaring to form a sharp edge along its longer circumference. I dumped the water on our flowerbed, tossed the flesh on the compost pile, and took the seed inside for one more wash under the faucet. It still smelled terrible. Josephine turned it over and over, then held it to her chest and did a little dance.

  I poured cooking oil into a cast-iron pan and Josephine plopped in the seed. We cooked it over a high flame until the oil started to smoke and the seed turned brown, then I flipped it over, turned the burner down low, and covered the pan.

  I’d read that it’s important to cook the seeds to denature their toxins. Ginkgotoxin is similar in structure to vitamin B6, and eating too much of it interferes with our ability to synthesize the vitamin. That can provoke a biochemical cascade that, especially in children, may lead to seizures, and even death. This sounds alarming, but it wasn’t enough to deter me. Before I started researching plant chemistry, I divided the world of potential foods into two categories: things that are poisonous and things that aren’t. But in reality everything is a little bit poisonous. It’s the dose that matters, not the poison. All plants defend themselves with toxins, but usually at such low levels that they are harmless, and might even be good for us. There is a hypothesis that our immune system has evolved to rely on a continual barrage of plant chemicals to fine-tune its production of antioxidants. In other words, the very thing that makes vegetables healthy may be the fact that they are trying to kill us.

  Ginkgo seeds, however, seemed more dangerous than, say, broccoli. But cooking is an effective way of breaking down the chemicals that plants construct (this can be a good or a bad thing, depending). To err on the side of caution, I let the seed cook in the pan for about fifteen minutes after turning down the flame. My hands were haunted by phantom itches while we waited. The power of suggestion was playing tricks on me, and though I’d been careful, some paranoid corner of my mind was convinced my fingers were about to break out into an itchy rash. Then, without thinking, I would rub my eyes and become intently aware of a prickling sensation around my eyelids.

  When I finally took out the ginkgo seed, it was blackened on both sides, and I could feel the nut rattling around inside the thin shell. It shattered under a little pressure from a nutcracker. Something small, brown, and misshapen fell onto the table and immediately broke into several pieces. It looked like something that had melted and then solidified, and perhaps it had. Josephine snatched a flake.

  “It’s yummy!” she exclaimed.

  I did not share her enthusiasm. The shard I crunched between my teeth was hard and tasteless, more like a shell than a nut. I picked up a mild burned odor and nothing else.

  Beth’s palate is several times more sensitive than mine, and she gingerly took the piece that Josephine offered and turned it over in her mouth.

  “Oh yeah, it is pleasant,” she allowed. “There is a sort of nuttiness.”

  Most of my piece had gotten stuck to my molars, and as it softened it became sweet and emitted a mild, toasty, butterscotch-like flavor. I must have cooked it so long that I’d not only denatured the toxins, but also caramelized the sugars in the seed. I’d have to try again, maybe with some instruction this time.

  Josephine took another small piece. “Mmm,” she said with drama. “I super love it.”

  In his book on the ginkgo, Peter Crane includes a list of the flavor descriptions he came across:

  “With a plump, soft, partly creamy, partly waxy white ‘meat’ not much bigger than a peanut, the ginkgo nut has a taste that has been variously described as like ‘mild Swiss cheese,’ ‘pine nuts,’ ‘potatoes crossed with sweet chestnuts,’ ‘green pea crossed with Limburger cheese,’ or just ‘fishy.’” Ginkgo nuts are sold in Chinatowns around the world as bai guo, often inauspiciously translated as “semen ginkgo.”

  Yum? Crane writes that he has encountered ginkgo nuts most often baked in their shells on a tray, or in tinfoil. But they show up in both sweet and savory dishes—soups, stir-fries, desserts—in many different Asian culinary settings. In Japan the tradition of eating ginkgo nuts with sake goes back to at least 1758, when it was mentioned in the Kaiseki-ryori-cho, a book on traditional foods.

  In the West you are more likely to hear about ginkgo as a medicine than as a food. In the popular imagination, it improves memory, prevents Alzheimer’s disease, and cures erectile dysfunction. But there’s good evidence only that it keeps blood vessels from constricting, perhaps aiding people who have insufficient blood flow in the brain. That is a common cause of dementia, so some doctors have suggested giving it to certain elderly patients.

  Ginkgo supplement pills are derived from the green leaves from trees on plantations. The owners of these plantations keep the trees stubby to ease harvesting. Supplement makers claim that ginkgo has been used in Chinese medicine for thousands of years. That’s true, but Chinese medicine employed the ginkgo nut, not the leaves. They used the seeds to prevent—among other things—drunkenness and hangovers. There’s little evidence it works. Doctors are still wary of ginkgo because the chemical dose in each pill varies widely from one extract to the next, with no standardization and little regulation.

  Ginkgo Cooked Right

  After I overcooked my ginkgo seed I was determined to find someone who could show me how they were supposed to taste. Josephine and I returned to the trees and filled a bag with seeds, which by this time were spotting the sidewalk. I cleaned them and then took them to Carolyn Phillips’s house, near San Jose. Phillips, a friend of a friend, had lived in Taiwan for eight years in the 1970s, and returned to the United States with a passion for Chinese food.

  Phillips met me at the door, offered me slippers to replace my shoes, and ushered me into a house filled with Eastern art. She had short blond hair and a gaze so avidly focused that I found myself unconsciously matching her intensity, breathlessly peppering her with questions, even before we had perched on the couch.

  Her husband, J. H. Huang, was as gentle as she was acute. He ghosted in, accepted introductions with a smile, expressed regret that I hadn’t been able to bring Josephine, then nodded to excuse himself and returned to his study, where he was reading Lao Tzu.

  I’d wanted to find someone who understood the culinary tradition behind the cooking of ginkgo nuts because all the recipes I’d found in English were written by Westerners experimenting rather than drawing on East Asian history and practice. Phillips was well positioned to serve as a translator of culinary tradition: When she arrived in Taipei she found herself in the nexus of Chinese food cultures. When the Communists took over mainland China, many of the wealthy nationalists moved to Taiwan, she told me, and they brought with them cooks representing every regional tradition. “
You have all the foods of China in one spot, all the most amazing foods. There were these incredible dining palaces. I just fell face-first into the cuisine.” She became a student of Chinese foods and recently poured everything she had learned into a cookbook: All Under Heaven: Recipes from the 35 Cuisines of China.

  As it turned out, there wasn’t much to cooking ginkgo, but Phillips had also prepared a small feast so I could try the seeds in the proper context. She had used store-bought, precleaned seeds, but when I produced mine she rolled them in a hot wok, toasting them like popcorn. The meat that emerged when we cracked them was bright green—like jade, she said—utterly different from the shriveled brown product of my overcooking. The seeds were, to my surprise, nearly tasteless, and a bit tacky. It was like eating stiff gnocchi. After all I’d read about the flavor of ginkgo, I’d expected them to be exciting and difficult, but they were mild and starchy, with just the faintest hint of bitterness. They were bitter in the way some beers are, pricking the taste buds just enough to make me take notice.

  It’s not all about flavor, Phillips told me. Chinese culinary theory seeks to balance taste, texture, and color. For instance, Phillips had made a stir-fry that emphasized textures, with water chestnuts (very crunchy), cooked celery (somewhat crunchy), ginkgo (gummy), and red goji berries (soft). The flavor was delicious, but the contrasting textures, now that I knew to pay attention to them, were even more interesting. She had also made ginkgo braised with Napa cabbage, which brought out a bit of bitterness in the seeds.