<P> In this context, humans used slash - and - burn agriculture to clear more land to make it suitable for plants and animals . Thus, since Neolithic times, slash - and - burn techniques have been widely used for converting forests into crop fields and pasture . Fire was used before the Neolithic as well, and by hunter - gatherers up to present times . Clearings created by the fire were made for many reasons, such as to draw game animals and to promote certain kinds of edible plants such as berries . </P> <P> Slash - and - burn fields are typically used and owned by a family until the soil is exhausted . At this point the ownership rights are abandoned, the family clears a new field, and trees and shrubs are permitted to grow on the former field . After a few decades, another family or clan may then use the land and claim usufructuary rights . In such a system there is typically no market in farmland, so land is not bought or sold on the open market and land rights are traditional . In slash - and - burn agriculture, forests are typically cut months before a dry season . The "slash" is permitted to dry and then burned in the following dry season . The resulting ash fertilizes the soil and the burned field is then planted at the beginning of the next rainy season with crops such as upland rice, maize, cassava, or other staples . Most of this work is typically done by hand, using such basic tools such as machetes, axes, hoes, and makeshift shovels . The old American civilizations, like the Inca, Maya, and Aztecs, also used this old agricultural technique . </P> <P> Large families or clans wandering in the lush woodlands long continued to be the most common form of life through human prehistory . Axes to fell trees and sickles for harvesting grain were the only tools people might bring with them . All other tools were made from materials they found at the site, such as fire stakes of birch, long rods (Vanko), and harrows made of spruce tops . The extended family conquered the lush virgin forest, burned and cultivated their carefully selected swidden plots, sowed one or more crops, and then proceeded on to forests that had been noted in their wanderings . In the temperate zone, the forest regenerated in the course of a lifetime . So swidden was repeated several times in the same area over the years . But in the tropics the forest floor gradually depleted . It was not only in the moors, as in Northern Europe, but also in the steppe, Savannah, prairie, pampas and barren desert in tropical areas where shifting cultivation is the oldest type of farming . Cultivation is similar to slash - and - burn . (Clark 1952 91--107). </P> <P> Southern European Mediterranean climates have favored evergreen and deciduous forests . With slash - and - burn agriculture, this type of forest was less able to regenerate than those north of the Alps . Although in northern Europe one crop was usually harvested before grass was allowed to grow, in southern Europe it was more common to exhaust the soil by farming it for several years . </P>

Who had developed a farming technique called shifting cultivation
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