Ancient centers of origin of plant and animal domestication — the nine homelands of food production — are indicated by the orange-shaded areas on the map. The most agriculturally productive areas of the modern world, as judged by cereals and major staples, are indicated by the yellow-shaded areas. Note that there is almost no overlap between the areas highlighted, except that China appears on both distributions, and that the most productive areas of the central United States today approach areas of the eastern United States where domestication originated. The reason why the two distributions are so different is that agriculture arose in areas to which the wild ancestors of the most valuable domesticable crops and animals were native, but other areas proved much more productive when those valuable domesticates reached them.
Source: Evolution, Consequences and Future of Plant and Animal Domestication, by Jared Diamond