The Origin and Transformation of Botanical Species

A seed pod inadvertently tossed on a rubbish pile, a half-eaten cob dropped from a child’s hand - these are the things of which revolutions are made. The transformation of the human race from gatherers to gardeners was certainly a slow, perhaps imperceptible, process. But in the history of the species we call us, there has been no single event of such profound and lasting significance as the coming of agriculture.

Prior to the advent of agriculture, our planet was a very different place from what we see today. The touch of human occupation was light and transitory on the land. Plant species existed in much greater diversity and tended to be far more restricted in range than is true today. And human beings, like all living things, were much more subject to the dynamics of nature. During good years there was abundance, at other times there was hunger. Agriculture, for better or worse, gave humans the ability to affect that seemingly irrefutable rule of nature.

Agriculture began where there existed varieties of plants with great value and in regions of rich soil, predictable rainfall and benevolent environmental conditions. By accident as much as by intuition, hunter-gatherers learned that by planting the seeds of favored species of plants, they could return and reliably harvest what they had sown. As a result, their nomadic range contracted and they tended to stay closer to the crops they were learning to cultivate.

Increasing skill and success at cultivation enabled ancient peoples to grow more food than they needed for day-to-day use. The existence of these surpluses had two complimentary effects. The need to store excess foodstuffs against leaner times compelled these early farmers to develop permanent settlements and the social structures needed to administer and defend them. Just as importantly, a predictable food supply led to steady increases in population. As more people came to occupy smaller pieces of ground, the process became irreversible; the hunter-gatherer lifestyle ceased to exist as a viable option.

It is perfectly correct to talk of the domestication of plants, but only with the understanding that the impact of human manipulation on selected plant species pales in comparison with the impact of cultivated plants on the human experience. Neolithic peoples who first domesticated plants were, themselves, domesticated by the process.

The earliest known permanent settlement is located at Jericho, a short distance north of the Dead Sea in Israel. Current estimates place the origin of jericho at 10,000 years ago (8000 B.C.). Wheat and barley were cultivated in the Zagros Mountains of Iraq about 9,000 years ago. From these early beginnings in the Fertile Crescent of the Middle East, agriculture developed in widely different locations and at different times in history, although the process was surprisingly similar.

In the beginning, people selected local plant varieties that grew easily, reliably and promised good yields. Prior to the widespread trade in botanical species, success depended on the availability of local plant types with these qualities, especially grains due to their high energy content and case of storage. Although not intentional in the beginning, plant selection was far from haphazard. Boston University archaeologist Richard MacNeish has described how this selection process might have worked:

In the course of their annual wanderings, a group of hunter-gatherers happens upon an especially well developed patch of, for example, wild squash. The largest, earliest fruits are gathered and returned to the base camp for consumption, in the process of which, seeds of these superior plants are scattered on the ground. Returning to the base camp the next year, the group may be surprised to find not just squash growing, but because superior fruits were “selected” and returned to camp the year before, plants with larger, earlier fruits than those found in the wild patch.

Although it could take generations, once the connection was made between plant and seed, and between superior seed and superior harvests, the process, and the attendant cultural and social changes involved, becomes an established way of life. The rest, it might be said, is prehistory.

Botanical Packrats

Over time agricultural techniques, tools and plant varieties were refined and improved. But it was the movement of species from place to place, and eventually the exchange of seed between different peoples in different areas that provided the variety needed to sever the final link with the natural food chain.

While agriculture eliminated the seasonal wanderings of some people, it contributed to major migrations of some early tribes. Damaged soils, climatic changes or pressure from neighbors covetous of the bounty of the fields forced some early people to move. And, of course, their valued seeds migrated with them. Humans proved to be botanical packrats, selecting, carrying and exchanging plant species as they moved about.
This cross-cultural trade in botanical species was the foundation upon which empires were built. Ancient Israel, Babylon and Egypt were founded on the cultivation of a variety of food plants - wheat, oats, barley, rye and lentils, as well as cotton and hemp for fiber, oil, animal feed, fertilizer and medicine.

Likewise, agriculture developed in Asia where millet and rice became staple foods, and in Central America where corn originated. In all of these cases, the result was the establishment and expansion of advanced civilizations.

God’s Grass

Because of the wealth of botanical species, the lack of complicating influences and its relative historical proximity to our own time, the developement of agriculture in the New World is instructive in how the process might have unfolded elsewhere.

The variety of plants that originated in the Americas has had a profound impact on agriculture worldwide. In both Central America and the Andean highlands of Peru, climate and soil conditions, the variety of edible species and ease of contact with neighbouring peoples encouraged the growth of agriculture and the abandonment of the hunter-gatherer lifestyle. The Tehuacan Valley of south central Mexico and the surrounding highlands gave rise to a number of important crop species. The mild climate, rich soil and adequate rainfall supported many indigenous edible plants such as several varieties of squash, pumpkins, chili peppers, amaranth, avacado and runner beans. Tobacco, which also orignated in the region, would become the first export crop of the English colonists in Virginia in the early 1600s.

But the most important contribution of the Tehuacan area was corn or zea maize. Maize was the foundation upon which the Zapotec, Olmec, Maya, Toltec and Aztec civilizations were built. Maize, actually tiny mishappen cobs, dated to Coxcatlan Cave in the Tehuacan Valley. Subsequent layers found at Coxcatlan and other locations reveal the effect of centuries of selection, with successive improvements in ear and grain size.

While the cultivation of maize was the setting stage for the cultural transformation that would lead to the establishement of the Mayan civilization, the plant itself was undergoing irreversible changes. Unlike its wild ancestors, the tighly packed and husked ears of modern corn are unable to release their load of seed without human aid. There are no known relatives of modern maize and it has been therorized that pollen from cultivated varieties may have passed the “tight ear” tract on to its wild bretheren, resulting in the extinction of the original line.

Another possiblity is that the original maize was a true breeding cross between several indigenous grasses. Whatever the cause, at some point maize became dependent on its human benefactors as they had become on it.

At roughly the same time that the proto-gardeners of Tehuacan Valley were experimenting with zea maize, a similar revolution was taking place in the Ayacucho Valley of Peru, where the predecessors of th great Andean civilizations were cultivating sweet potatoes, white potatoes, manioc (cassava), peanuts and beans.

The movement of botanical species in the New World, although less complex than that of most Old World species, is obscured both by the lack of a written language and by the intentional destruction by spanish conquerors of the art and culture of the native peoples of Central and South America. Whether maize travelled south with migrating people from Central America, the Chimu, who eventually settled on the narrow coastal plane of northern Peru, or was traded from group to group down the western coast of South America, the Mayan 'God's grass' was a primary crop of the early civilizations of the Andean highlands.

Ancient Enemies

The diffusion of maize and other botanical species northward can be traced along a string of archaeological sites from Mexico's central highlands to what is now the American Southwest. From the Aztec city of Tenochtitlan (Mexico City), north to Casas Grandes in western Chiahuaua state, to Chaco Canyon in northwestern New Mexico and Mesa Verde in southwestern Colorado, ruins and artifacts reveal well developed agrarian societies, as elsewhere in the Western Hemisphere, based on the cultivation of maize. The Chacoan culture of the Anasazi (Navajo for "ancient strangers,” or “ancient enemies”) arose from the seemingly barren soils about 900 A.D. and all but disappeared from the area by the late 1100s. Within that short span of time, these sturdy people raised buildings, constructed roads and established a complex social organization that was never surpassed by its neighbors.

Pueblo Bonito, the largest prehistoric building in the United States, was, at its completion in 1079, four stories high and contained more than 600 rooms and 40 kivas, circular structures of religious and/or cultural significance. Within a few miles of Pueblo Bonito in the Chaco Culture National Historic Park, are a number of smaller, but nearly as impressive. structures suggesting a local population numbering in the thousands.
Chaco was a political and cultural center for the region and appears to have been a commercial center as well. Four hundred miles of massive roads, averaging 30 feet in width, radiate out from Chaco, connecting with about 75 smaller communities throughout northwestern New Mexico. With its large population and scant resources of crop land and water, it seems likely that in a few hundred years Chacoan culture had moved from simple agriculture to a system based, at least in part on some form of commerce.

Aside from the resourcefulness of the people, the Anasazi owed much of their culture and way of life to the maize that had made its way from Central America to the Southwest and perhaps from there on to the eastern United States and as far north as Canada.

The Anasazi practiced what might he called guerilla gardening. Soil preparation was done with sharpened digging sticks and maize was planted in small, scattered patches. Recent evidence indicates, however, that Anasazi gardening techniques were anything but primitive.

DNA analysis by researchers at the University of Arizona of 800-year-old corn cobs found at several sites in southeastern Utah suggests the intentional development of hybrid varieties. Moreover, the similarities in the “hybridization signals" identified in samples from different locations suggests that these improved hybrids were readily traded between distant communities.

Despite their relative sophistication, however, these people were never able to fully overcome the harsh dictates of nature. The rapid rise and equally rapid decline of the Anasazi of the American Southwest speaks to the potential and the potential pitfalls of agrarian life. According to the most researchers, prolonged drought during the mid1200s led to the decline and eventual disappearance of Chacoan culture and other agrarian societies in the Southwest.

The Silk Road

Long before the Anasazi took their first tenuous steps toward an agricultural based society, the trade in botanical species was already transforming the Old World. The speed of plant species movement increased as empires expanded and mobility increased.

More than 2,000 years ago the Asian empires traded with the Greeks and Romans. Fleets of Chinese ships reached as far as the shores of Africa and Madagascar. The fall of the Roman Empire and the descent of the Dark Ages in Europe slowed EastWest trade to a trickle. It was not until Marco Polo re-established communication between Europe and China in the 13th century that the door was again opened.

At first the 'Silk Road," an overland route between Asia Minor and China. was the only passage. In the late 15th century a Portuguese navigator, Vasco da Gama, sailed around the Cape of Good Hope at the southern tip of Africa and made the first ocean voyage between Europe and India. At about the same time, Columbus, in an effort to reach Asia, sailed west and "discovered" the Americas. In the few centuries that have followed, the rate of species transfer has increased radically and has, in the process, changed the face of the Earth.

The effect of this has been phenomenal. New species introduced to strange lands compete with indigenous to the southeastern United States of the Japanese Kudzu vine. Kudzu was introduced to help control soil erosion and as an ornamental forage crop. The plant has flourished and is now threatening indigenous species due to its tendency to overrun them by sprawling and climbing.

In some cases the introduced species found its new habitat to be so hospitable and free of insect pests and diseases that growth rates and yields are considerably higher than in its original home. An example of this was the introduction of the rubber tree from its original habitat in the Amazon rain forest to the East Indies by the British in the 1870s. Attempts to grow rubber on plantations in the Amazon were a complete failure. Concentrations of rubber trees were vulnerable to attack by indigenous diseases and insects.

On the other hand, rubber plantations in the East Indies, being free of these pests, were successful, resulting in a great increase in the rubber available for the developing modern world. As in ancient times, this movement of plant species was not without its political and economic consequences. The British gained from the sale of rubber while Brazil suffered an economic collapse, all because of a handful of seeds that were carried from the Amazon, by way of Kew Gardens near London, to the plantations of the East Indies.

Burning Bridges

Modem agriculture has taken advantage of the diversity of plant species and varieties that come from the far corners of the Earth. Through selective breeding, many of the modern versions of these crops have been so altered that they often don't even resemble the original. The ability of plants to change and adapt is extraordinary.

Genetic engineering and other tools used to manipulate and alter plants promise to speed that process even further in the decades to come. At the leading edge, tissue culture laboratories propagate plant varieties to exacting standards using selected individual cells. Hydroponic techniques, especially the oxygen intensive aero-hydroponic method developed in Israel which is unequaled in the propagation of cuttings, play a significant role in the development and modification of plant varieties. These hydroponic methods are used at national labs, private research facilities and universities in the United States and worldwide for controlled plant propagation, seed generation and selective breeding experiments. The result is precise reproduction of specific plants and their unique properties including insect and disease resistance, adaptation to specific environmental conditions, uniform and simultaneous fruit ripening, and other desired characteristics.
There is, however, a price to pay for meddling with nature. Too often the new hybrids suffer weaknesses that can leave them vulnerable. Modern farms tend to grow a single variety of crop which is selected primarily for yield, appearance, uniform ripening and good shelf-life, not for taste or nutritional value.
The result of misguided hybridization and monocropping can be disastrous. One of the classic examples of how the process can go wrong was the introduction of the potato from its home in the Andes of South America to Western Europe. In Ireland the potato became such an important part of the diet that when blight infected the crop in 1845, it caused a famine that resulted in widespread disease, death and emigration. The potential for such catastrophes is not limited to the "bad old days," either. In 1970, a fungus attacked corn crops in the southeast and destroyed half of the crop from Texas to Florida, the crop was vulnerable because it was all one strain of corn that was not blight resistant.

But crop failure and famine may be the least of our problems. Today's ecological assault on Mother Earth is resulting in the loss of entire ecosystems, and many of the plant species indigenous to those lost regions. It is ironic that the very diversity of plant life that fostered the agricultural revolution is now threatened by the process. By the turn of the century, thousands of species will become extinct before we will even know of their existence. Moreover, many of the original varieties of our super-star crops are endangered or already lost.

The loss of natural genetic diversity is a tragedy of unimaginable proportions. Only with a broad selection of genotypes can we develop new varieties to meet as yet unforeseen changes in the environment. Some countries are recognizing the need to protect, propagate and store huge collections of genotypes and are putting some money into gene and seed banks - but it may be too little and too late. The loss that we have already suffered, we will never fully know. And with the steady destruction of natural habitat, that loss continues unabated.

To understand the dimensions of this tragedy, it is useful to return to the roots of civilization, to look again at an area where a benevolent environment and a great diversity of plant species combined with human ingenuity to bring about a revolution in the relationship of humans and the natural world they inhabit. Such a place can he found in the state of Oaxca in southern Mexico, the probable source of many of our most important food crops.

Twenty years ago Oaxaca was a rich and lush highland valley, still home to many of the species that flourished before the rise of the Mayans. Today, there is a clear change in the country and the climate. The once reliable rainy season comes late and rainfall is sparse. The river that once flowed year-round is now a muddy creek, at best, by the end of the dry season. The mountains have lost their natural forest cover due to the overuse of wood as a fuel for cooking. (This process began with the ancient inhabitants but has accelerated under increasing pressure from the region's growing population.) Oaxaca is becoming a highland desert and offers a tragic example of original genotype and habitat loss.
As you wander the isles of your local supermarket and try to find fruits and vegetables that are deliclous, nutritious and chemical free, you begin to appreciate why so many people are using home grown organically and hydroponically cultivated produce for a significant part of their diet. You, the home gardener, can cultivate plant varieties that a commercial grower would never consider, and thus contribute to genetic diversity.

Groups such as the California Rare Fruit Growers (CRFG), Seed Savers Exchange, Seeds of Change, and the North American Fruit Explorers (NAFEX), offer members an opportunity to cultivate unusual species and varieties. It is possible through these and other groups to acquire seeds and cuttings of ancient and endangered genetic stock.

Where governments have failed to recognize the importance of protecting habitat and genetic diversity, where multinational corporations run amok and trash everything that does not offer an immediate profit, we hobbyists may play a significant role in sustaining precious genetic stock for the future.