The Triumph of Seeds (2 page)

The second caveat acknowledges an area of seed controversy that lies beyond the scope and aim of this book. In graduate school, my curriculum included a one-credit seminar intended to familiarize students with the equipment used in a genetics laboratory. We met in the evenings once a week, donned white lab coats, and spent a couple of hours practicing with various tubes and pipes and whirring, beeping machines. As a simple exercise, the instructor showed us how to splice our own DNA into that of a bacterial cell. As the bacterial colony then divided and grew, our DNA would be copied ad infinitum, a basic form of cloning. Though of course we only used a tiny fragment of DNA and the results were crude, I distinctly remember thinking,
“I shouldn’t be able to clone myself in a one-credit class.”

The advent of relatively straightforward techniques for genetic manipulation has ushered in a new era for plants and their seeds. Familiar crops, from corn and soybeans to lettuce and tomatoes, have been experimentally altered with genes borrowed from arctic fish (for frost resistance), soil bacteria (to make their own pesticide), and even
Homo sapiens
(to produce human insulin). Seeds can now be patented as intellectual property, and designed to include
terminator genes
that prevent the ancient practice of saving seed for future plantings. Genetic modification is a pivotal new technology, but it will be
addressed only briefly in these pages. Instead, this book explores why we care so much in the first place. When modern genetics has also given us featherless chickens, glow-in-the-dark cats, and goats that produce spider silk, why is it that seeds are the focal point of the debate? Why do polls consistently find people more comfortable with the idea of changing their own genome, or the genomes of their children (for medical purposes), than they are with the notion of altering the genes in seeds?

The answers to these questions lie in a story that stretches back millions of years, wonderfully entwining the history of seeds with the history of our own species and culture. The challenge for me in writing this book lay not in filling it, but in deciding what material
to include and what must be left by the side of the road. (For additional anecdotes and information, be sure to read the notes for each chapter. They are the only place in the book, for example, where you will hear about gomphotheres, slippery water, or the piper’s maggot.) Along the way we will meet fascinating plants and animals as well as many people who have made seeds a part of their own stories, from scientists and farmers to gardeners, merchants, explorers, and chefs. If I have done my job right, you will see in the end what I have come to know, and what Noah apparently realized from the start: seeds are a marvel, worthy of our study, praise, wonder, and any number of exclamations points. (!)

INTRODUCTION

The Fierce Energy

Think of the fierce energy concentrated in an acorn! You bury it in the ground, and it explodes into a giant oak! Bury a sheep, and nothing happens but decay.

—George Bernard Shaw,

The Vegetarian Diet According to Shaw
(1918)

I
put the hammer down and peered at the seed. Not a scratch. Its dark surface looked just as smooth and perfect as it had when I’d found it on the floor of the rainforest. There, lying in the mud and mulch, surrounded by the sounds of water dripping and the constant chirr of insects, the seed had looked ready to burst open with the promise of bud swell, roots, and leafy green. Now, under the hum of fluorescent lights in my office, the damn thing seemed indestructible.

I picked up the seed and it settled neatly in my palm—a little larger than a walnut but flatter and dark, its heavy shell as hard as tempered steel. A thick seam ran lengthwise around the edge, but no amount of prodding and prying with a screwdriver had opened it so much as a crack. Vigorous squeezing with a long-handled pipe wrench hadn’t proved any better, and now hammer blows appeared to be useless. Obviously, I needed something heavier.

My university office took up a corner of the old Forestry Department herbarium, a largely forgotten place where dried plant collections lined the walls in dusty metal cabinets. Once a week, a group of retired faculty members gathered there for coffee and bagels, reminiscing about research trips, favorite trees, and departmental infighting from decades past. My desk, too, dated from an earlier era, a time when people built office furniture from welded steel, chrome, and double-weight Formica. It was large enough for a fleet of mimeograph machines and teletypes, and hefty enough to withstand the shockwaves of a nuclear attack.

Placing the seed close beside one of its hulking feet, I heaved the desk upward and let fly. It dropped with a resounding crash, launching the seed sideways to ricochet off the wall and skitter out of sight under a cabinet. When I retrieved it, the seed’s dark sides looked completely unscathed. So I tried again—
crash!
—and again—
crash!
—my frustration mounting with every failed attempt. Finally, I crouched down, pinned the seed between desk leg and wall, and started flailing at it wildly with the hammer.

My anger in that moment, however, didn’t come close to that of the red-faced forestry professor who suddenly stormed into the room, shouting, “What the hell is going on in here? I’m trying to teach a class next door!”

Clearly, I needed a quieter seed-breaking method. Particularly since it wasn’t just one seed that I needed to open. Two crates in the closet held hundreds of them, not to mention more than 2,000 leaves and bits of bark, each one painstakingly gathered over months of fieldwork in the forests of Costa Rica and Nicaragua. Transforming those samples into data would make up the bulk of my doctoral dissertation. Or not, as things were going.

Eventually, I discovered that a stout blow with a mallet and rock chisel would do the job nicely, but my struggle to open that first seed taught me an important evolutionary lesson. Why, I asked myself, would a seed’s shell be so impossibly hard to split? Wasn’t the whole point of a seed to throw itself wide and let the young plant spring
forth? Surely, that thick husk hadn’t evolved merely to thwart a hapless graduate student. The answer, of course, was as fundamental as a broody hen guarding her clutch of eggs, or a lioness defending her cubs. To the tree I was studying, the next generation meant everything, an evolutionary imperative worth any investment of energy and adaptive creativity. And in the history of plants, no single event has ensured the protection, dispersal, and establishment of their progeny more than the invention of seeds.

In business, people mark the ultimate success of a product by its brand recognition and universal availability. When I lived in a mud-walled hut in Uganda, four hours from a paved road, on the edge of a jungle called the Impenetrable Forest, I could still buy a bottle of Coca-Cola within a five-minute walk from my front door. Marketing executives fantasize about that kind of ubiquity, and in the natural world, seeds have it. From tropical rainforests to alpine meadows and arctic tundra, seed plants dominate landscapes and define entire ecosystems. A forest, after all, is named for its trees and not for the monkeys or birds that leap and flutter within it. And everyone knows to call the famed Serengeti a
grass
land—not a zebra-land with grass. When we pause to examine the underpinnings of natural systems, time and again we find seeds, and the plants that bear them, playing the most vital roles.

While an ice-cold soda tastes pretty good on a tropical afternoon, the Coca-Cola analogy only goes so far in explaining the evolution of seeds. But it is true in one more respect: natural selection, like commerce, rewards a good product. The best adaptations spread through time and space, in turn spurring further innovation in a process Richard Dawkins aptly called, “The Greatest Show on Earth.” Some traits become so widespread they seem axiomatic. Animal heads, for example, have two eyes, two ears, some kind of nose, and a mouth. Fish gills extract dissolved oxygen from water. Bacteria reproduce by splitting, and the wings of insects come in pairs. Even for biologists, it’s easy to forget that these fundamentals were once brand new, clever novelties spun from the sheer persistence of
evolution’s trial and error. In the plant world, the idea of seeds ranks right alongside photosynthesis as one of our chief assumptions. Even children’s literature takes the notion for granted. In Ruth Krauss’s classic book
The Carrot Seed
, a silent little boy disregards all naysayers, patiently watering and weeding around his planting until at last a great carrot sprouts up, “
just as the little boy had known it would.”

Though famous for how its simple drawings transformed the genre of picture books, Krauss’s story also tells us something profound about our relationship with nature. Even children know that the tiniest pip contains what George Bernard Shaw called “fierce energy”—the spark and all the instructions needed to build a carrot, an oak tree, wheat, mustard, sequoias, or any one of the estimated
352,000 other kinds of plants that use seeds to reproduce. The faith we place in that ability gives seeds a unique position in the history of the human endeavor. Without the act and anticipation of planting and harvest, there could be no agriculture as we know it, and our species would still be wandering in small bands of hunters, gatherers, and herdsmen. Indeed, some experts believe that
Homo sapiens
might never have evolved at all in a world that lacked seeds. More than perhaps any other natural objects, these small botanical marvels paved the way for modern civilization, their fascinating evolution and natural history shaping and reshaping our own.

We live in a world of seeds. From our morning coffee and bagel to the cotton in our clothes and the cup of cocoa we might drink before bed, seeds surround us all day long. They give us food and fuels, intoxicants and poisons, oils, dyes, fibers, and spices. Without seeds there would be no bread, no rice, no beans, corn, or nuts. They are quite literally the staff of life, the basis of diets, economies, and lifestyles around the globe. They anchor life in the wild, too: seed plants now make up more than 90 percent of our flora. They are so commonplace it’s hard to imagine that for over 100 million years other types of plant life dominated the earth. Roll back the clock and we find seeds evolving as trivial players in a flora ruled by spores, where tree-like club mosses, horsetails, and ferns formed
vast forests that remain with us in the form of coal. From this humble beginning, the seed plants steadily gained advantage—first with conifers, cycads, and ginkgos, and then in a great diversification of flowering species—until now it is the spore bearers and algae that watch from the sidelines. This dramatic triumph of seeds poses an obvious question: Why are they so successful? What traits and habits have allowed seeds, and the plants that bear them, to so thoroughly transform our planet? The answers frame the narrative of this book and reveal not only why seeds thrive in nature, but why they are so vital to people.

Seeds Nourish.
Seeds come pre-equipped with a baby plant’s first meal, everything needed to send forth incipient root, shoot, and leaf. Anyone who has ever put sprouts on a sandwich takes this fact for granted, but it was a critical step in the history of plants. Concentrating that energy into a compact, portable package opened up a huge range of evolutionary possibilities and helped seed plants spread across the planet. For people, unlocking the energy contained in seeds paved the way for modern civilization. To this day, the foundation of the human diet lies in co-opting seed food, stealing the nourishment designed for baby plants.

Seeds Unite.
Before seeds, plant sex was pretty dull stuff. When they did it at all, plants made sure the act was quick, out of sight, and usually with themselves. Cloning and other asexual means were common, and whatever sex happened rarely mixed genes in a predictable or thorough way. With the advent of seeds, plants suddenly began breeding in the open air, dispersing pollen to egg in increasingly creative ways. It was a profound innovation: unite the genes from two parents on the mother plant and package them into portable, ready-to-sprout offspring. Where spore plants interbred only occasionally, seed plants mixed and remixed their genes constantly. The evolutionary potential was enormous, and it’s no coincidence that Mendel solved the mystery of inheritance by a close examination of pea seeds. Science might still be waiting to understand genetics if that famed pea experiment had instead been “Mendel’s Spores.”

Seeds Endure.
As any gardener knows, seeds stored through the winter months can be planted the following spring. In fact, many seeds require a cold spell, a fire, or even passage through an animal gut to trigger their germination. Some species persist in the soil for decades, sprouting only when the right combination of light, water, and nutrients makes conditions right for plant growth. This habit of dormancy sets seed plants apart from nearly all other life forms, allowing great specialization and diversification. For people, mastering the storage and manipulation of dormant seeds paved the way for agriculture and continues to determine the fate of nations.

Seeds Defend.
Almost any organism will fight to protect its young, but plants equip their seeds with an astonishing and sometimes deadly assortment of defenses. From impenetrable husks and jagged spikes to the compounds that give us hot peppers, nutmeg, and allspice, not to mention poisons like arsenic and strychnine, seed defenses include some surprising (and surprisingly useful) adaptations. Exploring this topic illuminates a major evolutionary force in nature and shows how people have co-opted seed defense for their own ends, from the heat in Tabasco sauce to pharmaceuticals to the most beloved seed products of all, coffee and chocolate.

Seeds Travel.
Whether tossed up by storm waves, spun on the wind, or packaged in the flesh of a fruit, seeds have found countless ways to get around. Their adaptations for travel have given them access to habitats spanning the globe, spurred diversity, and led people to some of the most essential and valuable products in history, from cotton and kapok to Velcro and apple pie.