The Triumph of Seeds (3 page)

This book is both an exploration and an invitation. Like seeds themselves, it began as something small, an interest that grew with my own curiosity, following the winding path that seeds have paved through evolution, natural history, and human culture. From the jungles and laboratories of my own research, and at the insistence of my seed-obsessed son, I plunged in and let the story unfold, guided by the gardeners, botanists, explorers, farmers, historians, and monks I met along the way—not to mention the wonderful plants themselves,
and the menagerie of animals, birds, and insects that depend upon them. But for all the fascinating tales of seeds in nature, one of their hallmarks is that we don’t have to look far to find them. Seeds are an integral part of our world too. So whether you prefer coffee and chocolate-chip cookies or mixed nuts, popcorn, pretzels, and a glass of beer, I invite you to sit down with your favorite seed-derived snacks, and let the journey begin.

Seeds Nourish

Oats, peas, beans and barley grow,

Oats, peas, beans and barley grow,

Can you or I or anyone know

How oats, peas, beans and barley grow?

First the farmer sows his seed,

Stands erect and takes his ease,

He stamps his foot and claps his hands,

And turns around to view his lands.

—Traditional folk song

CHAPTER ONE

Seed for a Day

I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders.

—Henry David Thoreau,

The Dispersion of Seeds
(1860–1861)

W
hen a pit viper strikes, physics tells us it can’t lunge forward farther than the
length of its own body. The head and front end are agile, but the tail of the beast stays put. Anyone who has been struck at, however, knows that these snakes can fly through the air like Zulu spears, or the daggers thrown in ninja movies. The one coming at me darted up from a mat of dead leaves, launching itself at my boot in a lightning blur of fangs and intent. I recognized it as a fer-de-lance, a snake famed throughout Central America for its unfortunate combination of strong venom and a short temper. In this individual’s defense, however, I must confess that I had been poking it with a stick.

Surprisingly, the study of rainforest seeds can involve a lot of snake-poking. There is a simple explanation for this: science loves a straight line. Lines, and the relationships they imply, pop up everywhere, from chemistry to seismology, but for biologists the most common line of all is the transect. Whether one is counting seeds,
surveying kangaroos, spotting butterflies, or searching for monkey dung, following an arrow-straight transect across the landscape is often the best way to make unbiased observations. They’re great because they sample everything in their path, cutting directly through swamps, thickets, thorn bushes, and anything else we might otherwise prefer to avoid. They’re also horrible because they sample everything in their path, cutting directly through swamps, thickets, thorn bushes, and anything else we might otherwise prefer to avoid. Including snakes.

F
IGURE
1.1.  A fer-de-lance
(Bothrops asper)
. Anonymous (nineteenth-century). R
EPRODUCTION
© 1979
BY
D
OVER
P
UBLICATIONS
.

Ahead of me, I heard the ring of machete on vine as my field assistant, José Masis, slashed us a path through the latest jungle impediment. I had time to listen because the snake, having missed my boot by inches, did something extremely disconcerting. It disappeared. The mottled browns of a fer-de-lance’s back make an excellent camouflage, and I never would have seen so many of them—not to mention eyelash vipers, hog-nosed pit vipers, and the occasional boa constrictor—if I hadn’t been diligently walking straight lines through the forest, bent low to the ground, rummaging through the
leaf mulch. Some transects seemed to hold more snakes than seeds, and José and I developed techniques for nudging them out of the way or even lifting them on sticks and tossing them gently aside. Now, with an angry, invisible viper somewhere at my feet, new questions emerged. Was it best to stand still and hope the snake wasn’t repositioning itself for another strike? Or should I run, and if so, in which direction? After a tense minute of indecision I ventured a step, then two. Soon I had resumed my seed transect without incident (though not before cutting myself a much longer snake-poking stick).

Scientific research often combines moments of excitement and discovery with long periods of monotonous repetition. More than an hour passed before my slow searching turned up the day’s reward. There, directly in the path before me, sprouted a seedling of the great
almendro
, a towering tree whose fascinating natural history had
drawn me to this
rainforest in the first place. Though unrelated to the nut trees of North America and Europe, the name translates to “almond,” a reference to the fatty seeds at the center of each fruit. I noted the tiny plant’s size and location in my field book, and then crouched down for a closer look.

F
IGURE
1.2.  The sprouting seed of an
almendro
tree (
Dipteryx panamensis
). P
HOTO
© 2006
BY
T
HOR
H
ANSON
.

The seed’s shell, so difficult to open in the lab, lay upended in halves, neatly split by the pressure of the growing sprout. A dark stem arched downward into the soil, and above it two seed leaves had begun to unfurl. They looked impossibly green and tender, a rich meal for the pale shoot just visible between them. Somehow, this tiny speck had the potential to reach the forest canopy far above me, its first steps fueled entirely by the energy of the seed. That same story repeated itself everywhere I looked. Plants lay at the heart of the rainforest’s great diversity, and the vast majority of them had started out exactly this same way, the gift of a seed.

For the
almendro
, the transformation from seed to tree seemed particularly incredible. Mature individuals often exceed 150 feet (45 meters) in height, with buttressed trunks 10 feet (3 meters) across at the base. They live for centuries. Their iron-hard wood is known to dull or even break chainsaws, and when they flower, vivid purple blossoms festoon their crowns and rain down to carpet the ground below. (In my first scientific presentation on the tree, I lacked a decent photo of its flowers, but got the point across with the closest approximation of the color that I could find: a Marge Simpson wig.)
Almendro
trees produce so much fruit they are considered a keystone species, vital to the diets of everything from monkeys to squirrels to the critically endangered Great Green Macaw. Their loss could alter the ecology of a forest, leading to a cascade of changes, and even to local extinctions for the species that depend upon them.

I was studying the
almendro
because throughout its range, from Colombia north to Nicaragua, the tree has faced increasing challenges as forests have been cleared for ranching and agriculture, and as demand has increased for its dense, high-quality timber. My research focused on the survival of
almendros
in Central America’s
rapidly developing rural landscape. Could it persist in small fragments of rainforest? Would the flowers still be pollinated, the seeds be dispersed, and the next generations be genetically viable? Or were the majestic old trees that were now isolated in pastures and forest patches merely “the living dead”? If these giants couldn’t reproduce successfully, then all of their complex relationships with other forest species would begin to unravel.

The answers to my questions lay in the seeds. So long as José and I could find enough of them, their genetics could tell us the rest of the story. Every seed and seedling we encountered held clues about its parents coded into its DNA. By carefully sampling and mapping them in relation to the adult
almendros
, I hoped to find out just which trees were breeding, where their seeds were going, and how those things changed as the forest was carved into fragments. The project lasted for years and involved six trips to the tropics, thousands of specimens, and countless hours in a laboratory. At the end I had a dissertation, several journal articles, and some surprisingly hopeful news about the future of the
almendro
tree. But only after all the samples were analyzed, the papers written, and the diploma delivered did I realize that something fundamental was missing. I still didn’t really understand how seeds worked.

Years passed, other research projects came and went, but still this mystery puzzled me. While everyone from gardeners and farmers to the characters in children’s books trust that seeds will grow, what makes it happen? What lies inside those neat packages just waiting for the spark to build a new plant? When I finally decided to get to the bottom of these questions, my mind immediately pictured that sprouting
almendro
tree, and how every part of its big seed was clearly visible, like the image in a textbook. Popping down to Costa Rica to find a fresh one was out of the question, but
almendro
is far from the only species with large, easily sprouted seeds. In fact, nearly any grocery store, fruit stand, or Mexican restaurant keeps the big seeds (and surrounding fruit) of at least one rainforest tree always in good supply.