<P> The indigenous people in what is now California and the Pacific Northwest practiced various forms of forest gardening and fire - stick farming in the forests, grasslands, mixed woodlands, and wetlands, ensuring that desired food and medicine plants continued to be available . The natives controlled fire on a regional scale to create a low - intensity fire ecology which prevented larger, catastrophic fires and sustained a low - density agriculture in loose rotation; a sort of "wild" permaculture . </P> <P> A system of companion planting called the Three Sisters was developed in North America . Three crops that complemented each other were planted together: winter squash, maize (corn), and climbing beans (typically tepary beans or common beans). The maize provides a structure for the beans to climb, eliminating the need for poles . The beans provide the nitrogen to the soil that the other plants use, and the squash spreads along the ground, blocking the sunlight, helping prevent the establishment of weeds . The squash leaves also act as a "living mulch". </P> <P> From the time of British colonization of Australia in 1788, Indigenous Australians were characterised as nomadic hunter - gatherers who did not engage in agriculture, despite evidence to the contrary . In 1969, the archaeologist Rhys Jones proposed that Indigenous Australians engaged in systematic burning as a way of enhancing natural productivity, what has been termed fire - stick farming . In the 1970s and 1980s archaeological research in south west Victoria established that the Gunditjmara and other groups had developed sophisticated eel farming and fish trapping systems over a period of nearly 5,000 years . The archaeologist Harry Lourandos suggested in the 1980s that there was evidence of' intensification' in progress across Australia, a process that appeared to have continued through the preceding 5,000 years . These concepts led the historian Bill Gammage to argue that in effect the whole continent was a managed landscape . </P> <P> In two regions of Australia, the central west coast and eastern central Australia, forms of early agriculture may have been practiced . People living in permanent settlements of over 200 residents sowed or planted on a large scale and stored the harvested food . The Nhanda and Amangu of the central west coast grew yams (Dioscorea hastifolia), while various groups in eastern central Australia (the Corners Region) planted and harvested bush onions (yaua - Cyperus bulbosus), native millet (cooly, tindil--Panicum decompositum) and a sporocarp, ngardu (Marsillea drumondii). </P>

What three factors probably played a role in the origins of agriculture