AGRICULTURE: A GENERAL SURVEY. Agri culture is so primitive and fundamental an art, the beginnings of which so far precede any documents, that any attempt to write its earliest history becomes a matter of surmise and un verifiable conclusions from general principles. It is reasonable to suppose that prehistoric hunter man began by learning to tame the young of certain species, which proved to be fertile in cap tivity and could be attached to his wanderings. At probably a later stage tribes that gathered certain grains of food value began to make provision for future years by scattering a portion of the seed and effecting some rough clearance of the soil. They took the desirable grains with them in their wanderings and by sowing them they learned to become independent of return to the original centres of growth. When any remains of the early settlements emerge, they reveal evidence of animals and cultivated plants. For example, predynastic tombs in Egypt, an early Sumerian house in Mesopotamia (3500 B.c.), and lake dwellings in Switzer land and Italy associated with neolithic man, have yielded grains of wheat of a comparatively advanced type, which must have been preceded by long ages of culture. Flax and barley were also grown. It is significant, however, that no wild species can be as signed as the origin of any of our widely cultivated plants and the same complexity and uncertainty gathers round the sources of the domesticated horses, sheep, oxen and pigs. With the excep tion of maize and barley, the cultivated plants are polyploids, i.e., the number of chromosomes in the cells is a multiple of the diploid number which characterizes the normal species. This points to a probable hybrid source ; but whatever the origin, the polyploidy provides material susceptible of the variation on which selection can work, even when it is not attended by giantism or an excess of vigour which would naturally draw the attention of the early cultivator. Though no wild species can be fixed upon as a starting point of our cereals, Vaviloff has argued that the exist ing distribution of varieties points to certain centres as the orig inal fountain of the cultivated races, these being regions which are to-day characterized by a concentration of varieties in the culti vated fields, where a host of forms occur not yet segregated into distinct races and shade off into weed forms which equally in habit the uncultivated land. Vaviloff thus indicates the highlands of south-western Asia, particularly Afghanistan, as the probable centre of the soft and club wheats; northern Africa as the home of durum wheats, while einkorn, a primitive wheat cultivated in prehistoric times, may have had its origin in Asia Minor. Still another race, emmer, perhaps the most ancient of cereals, is found in patches all over the old world and only among isolated and backward peoples.
But if we can arrive at some conclusions respecting the earliest forms of our cultivated plants and animals, the history of the growth of husbandry must ever remain a blank. When agriculture does emerge in written history in the time of the Greeks and Romans (see GEOPONICI), it is already a highly developed art, which had behind it long centuries of empiric progress, the fruit of observation and of trial and error. Cato, Varro, Virgil, Colu mella, the elder Pliny, describe an elaborate system of farming, embodying many principles, such as the value of leguminous crops as a preparation for wheat, for which modern science has only recently found an explanation. The methods of growing corn, vines and olives then prevailing had not been substantially altered down to the middle of the 19th century, and the sculp tured representation of a sacrificial bull, lamb and boar on the plutei of Trajan in the Roman Forum bear witness to an advanced state of stock breeding. Roman agriculture is indeed the founda tion of modern farming, and though over the greater part of Europe it became submerged with the irruption of the barbar ians, its traditions probably never died out in the favoured re gions, but shaped and were resumed in modern systems of farming.