114). They taste bitter due to the presence of amygdalin, the precursor to cyanide. The chemical serves as a defense mechanism for the almond, deterring animals (and people) from eating them and better ensuring the propagation of the almond plant because the nut is its seed. As Diamond points out, if animals feasted indiscriminately on almonds they would minimize the chances that the plant would propagate itself. However, "occasional individual almond trees have a mutation in a single gene that prevents them from synthesizing the bitter-tasting amygdalin," (p. 118). In the wild those non-bitter almond trees would die out because birds feast on their seeds before they can sprout. Children of early farmers, though, might have gladly munched on some of the sweet almonds and brought the seeds back to their parents. Any sweet almonds that were thrown aside or purposely planted would enjoy the benefits of cultivation.

The story of the oak is different even though like almonds, most wild acorns are bitter. Acorns are not poisonous, contain valuable nutrients, and the occasional oak tree produces acorns low in tannins and pleasant to eat. However, oak trees "have three strikes against them," (Diamond p. 129). First, it takes at least a decade for an acorn to mature into a tree that produces more nuts. Almond trees reach maturity in just a few years. Second, squirrels dominate the acorn market. Any seeds squirrels miss grow into oak trees, and "we humans didn't stand a chance of selecting oaks for the acorns that we wanted," (p. 129). Squirrels are fast to gather and hoard acorns. Humans have a much better chance at finding sweet wild almonds than sweet wild acorns. Third, cultivating oak trees for food is impossible because planting a sweet acorn will not yield a sweet acorn oak tree. Bitterness in oak trees is due to a multitude of genes, not a single gene as it is in almonds.

13. Animal domestication is like marriage, suggests Diamond. To survive, they both need to fulfill all of a set of necessary criteria. Tolstoy suggested in Anna Karenina that "Happy families are all alike; every unhappy family is unhappy in its own way,"...

157). Similarly, domesticated animals are all alike, and every undomesticated animal is so in its own way. "To be domesticated," notes Diamond, "a candidate wild species must possess many different characteristics," the lack of any of which would doom domestication (p. 169). This is what the author refers to as the Anna Karenina principle of animal domestication. The principle helps account for why geography enabled some civilizations to remain at the hunter-gatherer stage while encouraging others to become large, stable societies organized around farming and animal husbandry. Diamond identifies the following six essential features for animal domestication, although the list is not exhaustive: diet, growth rate, captive breeding problems, nasty disposition, tendency to panic, and social structure. If a wild species is deficient in any one of these categories, it will be unsuitable for domestication. The animals indigenous to any given area therefore determine whether humans living in that area will be able to create sedentary societies based on animal domestication and agriculture.
20. Diamond explains China's "chronic unity" and Europe's "chronic disunity" in geographical terms (p. 414). Like the Fertile Crescent, China had a head start on agriculture and animal domestication, giving rise to some of the earliest civilizations on the planet. The diversity among Chinese languages belies the fact that several dialects can be traced to a single parent language. Cultural factors like language spread throughout East Asia and fostered political unity. Geography also enabled political unity in China, whereas geography hindered political unity in Europe. Unlike Europe, China has a relatively smooth coastline and a few central rivers. After China became unified in 221 BC, it remained so. The disunity of Europe and the unity of China had powerful consequences for world history, especially during the age of exploration and colonization. The strong centralized government in China prevented exploration whereas explorers in Europe were able to petition for funds from various governments. China's head start on agriculture…