17 Reading 3-1 The steppes tend to be marginal, and they are an unlikely place to begin. The few domestic plants that might be of steppic origin are Panicum miliaceum , Setaria italica , and Cannabis sativa . One invaluable contribution, however, came from Aegilops squarrosa , a plant of the central Asian steppes that provided the D genome of hexaploid wheat. This may be why wheat can be grown on such a scale on the temperate steppes of the world. The tropical rain forests, Fig. 4, provide a very dif f cult environment. We do not know of a single hunting-gathering society of rain forests that does not require some supplementation from cultivated plants (Bailey et al., 1989). We have no evidence of early occupation of either the Amazonian or African rain forest. Certainly, the present rain forest of Amazonia has been strongly modi f ed by activities of farming people and does not represent the original conditions faced by the f rst colonizers. It is probable that agricul ture must f rst be developed and adapted to this dif
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