climate. cially high percentage of annual plants. The combination of these two factors—a high diversity of species and a high percentage of annuals—means that western Eurasia's Mediterranean zone is the one with by far the highest diversity of annuals. The significance of that botanical wealth for humans is illustrated by the geographer Mark Blunder's studies of wild grass distributions. Among the world's thousands of wild grass species, Blumler tabulated the 56 with the largest seeds, the cream of nature's crop: the grass species with seeds at least 10 times heavier than the median grass species (see Table 8.1). Virtually all of them are native to Mediterranean zones or other seasonally dry environments. Furthermore, they are overwhelmingly concentrated in the Fertile Crescent or other parts of western Eurasia's Mediterranean zone, which offered a huge selection to incipient farmers: about 32 of the world's 56 prize wild grasses! Specifically, barley and emmer wheat, the two earliest important crops of the Fertile Crescent, rank respectively 3rd and 13th in seed size among those top 56. In contrast, the Mediterranean zone of Chile offered only two of those species, California and southern Africa just one each, and southwestern Australia none at all. That fact alone goes a long way toward explaining the course of human history. A third advantage of the Fertile Crescent's Mediterranean zone is that I 4 O • GUNS, GERMS, AND STEEL table 8.1 World Distribution of Large-Seeded Grass Species Area Number of Species West Asia, Europe, North Africa 33 Mediterranean zone 32 England 1 East Asia 6 Sub-Saharan Africa 4 Americas 11 North America 4 Mesoamerica 5 South America 2 Northern Australia 2
