People who are knowledgeable about such things estimate that multicellular photosynthetic organisms – plants – made it onto land during the Silurian Period in geologic history. During the past 450 million years or so, terrestrial plants diversified into more than 300,000 living species. Of these, the most successful group today is the flowering plants, which account for about 275,000 known species. Only a small fraction, about 7,000 species, are used for agricultural purposes and of these, 30 make up most of the world’s staple food sources. Wheat, corn and rice account for more than half of the daily calories humans consume today.
At some point during the evolution of human societies, someone somewhere realized that discarded seeds sometimes sprouted and could provide a staple food source without having to move onto new areas in search of food. Where agricultural settlements began in human history is not entirely clear but anthropological data point to the “Fertile Crescent” of the Near East as the center of wheat- and barley-based settlements about 10,500 years ago. A few years ago there was quite an excitement (well, at least among those who get excited by such things!), when Israeli scientists discovered what appeared to be carbonized remains of domesticated figs in the Lower Jordan Valley, near Jericho. Although the findings were not universally accepted, if true, these artifacts push the evidence for purposeful planting of crop plants about 1,000 years before that in the Tigris-Euphrates Rivers region. Around the world, archeologists postulate many centers of origin for agriculture at different times. In addition to the Near East, Northern China is thought to have the second oldest center at 9,000 years ago, followed by Central Mexico (5,700 years ago), the Andes region of South America around 5,200 years ago, and West Africa and North America about 4,500 and 4,000 years ago, respectively. Two basic types of agricultural systems have been proposed: seed crops, such as wheat, maize, rice, barley, etc., which are labor-intensive and more vulnerable to natural disasters (e.g. hail, locusts, floods) that lead to crop failure, and “vegeculture”, in which root and tree crops, lke avocado, manioc, yam and potato are grown. These require less manual labor and is less subject to large-scale destruction by natural forces but the caloric value of the foods they produce is also generally less.
Scholars sometimes argue over what the first crops were and where they were first domesticated. With the discovery of the fig remains, archeologist Ofer Bar-Yosef was quoted in a June 2, 2006, New York Times article: “Eleven thousand years ago, there was a critical switch in the human mind – from exploiting the earth as it is, to actively changing the environment to suit our needs. People decided to intervene in nature and supply their own food rather than relying on what was provided by the gods.” In other words, people learned to exploit plants. But there is another way to look at this. In a beautifully written book, “The Botany of Desire,” author Michael Pollen argues: “we automatically think of domestication as something we do to other species, but it makes just as much sense to think of it as something certain plants and animals have done to us, a clever evolutionary strategy for advancing their own interests.” Those interests, of course, includes protection and dispersal by humans.
Whoever exploited whom is a matter for semantics debate. Just the same, some people are interested in the origins of crops for more practical than philosophical reasons. One of the individuals who had done an extraordinary amount of work on the origins of cultivated plants was the Russian scientist, Nikolai Ivanovich Vavilov. Inspired by the writings of the Swiss botanist, Alfonse DeCandolle on plant geography, Vavilov spent most of his scientific life traveling around the world, collecting, saving, and cataloguing seeds and other plant specimens. Whereas DeCandolle, son of a protestant minister and a devout Creationist, believed that each new species arose from a specially “created” individual, Vavilov embraced Darwinian evolutionary concepts. Having spent some time in the laboratory of the renowned British biologist, William Bateson, Vavilov was well-versed in the modern 20th century science of evolutionary genetics. As a result of his world-hopping journeys and keen observations, Vavilov eventually mapped 8 centers of origins for domesticated grain crops. He proposed both primary and secondary centers of origin for many important cereals. In a 1926 essay, for example, he writes: “…bottom cultivated wheat has two centers of origin: North Africa and southwest Asia…during very ancient times Egypt and other countries in North Africa had developed their own groups of cultivated wheat, sharply isolated from Asiatic wheat.” Vavilov could make such claims because he actually traveled to these places to examine not only the cultivated varieties but also their “wild” relatives. And he made another valuable contribution: he postulated that the centers of origin should be the sources of greatest genetic variability. He proposed that many wild relatives of modern crops should be able to be located in mountainous areas, as these would offer the greatest degree of environmental variation and, thus, harbor the greatest genetic diversity in the population. This “gene pool” could then be the source of new, improved varieties of crops.
Modern crop science is a multibillion dollar business. Biotechnology promises to revolutionize agriculture, but such claims have been made before, as was the case with the “Green Revolution.” Traditional breeding programs may be slower but rely on genetic heterogeneity as the source of variation. For example, rice is not one uniform crop. There are roughly 40,000 different varieties of rice, belonging to 4 main categories: indica, japonica, aromatic, and glutinous. Each variety has slightly (or vastly) different genetic characteristics. In addition to nutritional value, taste, aroma, and stickiness upon cooking, there are also variations in yield, disease resistance, and ease of cultivation. These variations represent “insurance policies” because monoculture may lead to complete crop failure as the result of a single environmental change.
Vavilov recognized the importance of these genetic variations and spent three decades in identifying, collecting and storing seeds from all over the world in his Institute of Plant industry in St. Petersburg, Russia (later Leningrad, then Stalingrad in the Soviet Union; Petersburg again today in the Russian Federation). He looked at his collection as a savings account, a bank deposit of genetic diversity to be drawn upon in the development of new crop varieties. The idea caught on and there are about 1,400 seed banks around the world today. The three largest ones include the Millenium Seed Bank in London, the Svalbard Global Seed Bank in Norway, and Vavilov’s seed bank in Russia. Other smaller, more specialized centers are the International Center for Tropical Agriculture (cassava, beans) in Coli, Colombia; the International Potato Center in Lima, Peru; the International Institute for Tropical Agriculture (cowpea, yams, soybeans) in Nigeria; and The International Rice Research Institute in the Philippines, which houses about 100,000 rice samples in its gene bank collection. The Millenium Seed Bank in England is by far the largest repository of plant samples, consisting of about 100 times more specimens than the one in Norway. The Svalbard Seed Bank opened in 2008 in a converted old mine near the Arctic Circle. A joint venture between the Global Crop Diversity Trust, the Consultive Group on International Agriculture, the Norwegian government, and private donors, 400,000 seed samples, representing about one-third of the world’s most important food crop varieties, are housed in a climate-controlled, earthquake- and nuclear bomb-proof facility. Seeds are classified as “orthodox” or “recalcitrant.” Orthodox seeds can stay viable for very long periods of time. For example, date palm seeds as old as 2,000 years have been successfully germinated and there is a recent report from Russia that 32,000 year-old seeds from the permafrost of Siberia have been found to be viable. Recalcitrant seeds can not be maintained for long periods and must be continuously grown and harvested. Either way, these so-called gene banks represent food security for a hungry world. These natural sources of variation are likely to represent the most important savings accounts for the foreseeable future. The seed banks guard something far more precious than gold or money: they are the depositories of sustenance on which humans and other animals depend.