Been reading Jared Diamond's Guns, Germs, and Steel (thanks you, Dave!), and so far, one observation has really jumped out at me. Human domestication of plants hasn't really been a process particularly directed by humans. That is, it's not as though we sorted through species, picked the characteristics we wanted from farm crops, and set about carefully crossing the most promising specimens. Rather, it was more that we went out and picked and ate the things we were able to. The species which were set up to take advantage of this new distribution system "followed" us, as it were (through the magic of our digestive system or general human clumsiness) more or less until we noticed them and decided to start growing them more carefully. At which point, it wasn't as though we really did all that much to predictably control the direction of their evolution. No. Whatever our cultivation techniques were -- however wise or idiotic, whatever they were -- the plants that fit in best with the company line were strongly selected for just because they were the only ones we'd actually notice, harvest, and eat.
For example, most wild wheat stalks will explode when ripe, to scatter seeds. It's only the occasional mutant which stays in one place. It just so happens that people are only going to harvest and eat whole stalks -- because who even notices individual wheat grains? All of a sudden, this one particular mutant gets selected for, to the tune of being lovingly replanted and tended to, year after year, and within a thousand years or so, we've got domesticated wheat that hangs onto its grains, doesn't sheathe them in protective coats, all ripens more or less at the same time, and generally does its best to satisfy the bizzare demands of its new environemnt. And gets genetically rewarded like a cereal out of hell for its efforts. Discussion of "genetically modified" foods is a bit strange in this light: most modern crops are amazingly unlike their ancestors, it turns out. Corn, for example. It used to be that corn cobs were roughly the same size as modern corn kernels. Or, did you know that sheep used to have long legs? It just kind of happened that the sheep who couldn't run away as well were the ones that were more easily herded. And so on and so forth. Kind of puts certain things in a new light.