Four hundred years ago, Coffea arabica, a tropical shrub bearing glossy green leaves and bright-red berries, was virtually unknown outside of the Arab world and the corner of Ethiopia where it had been discovered in the ninth century—by a goatherd who, legend has it, noticed that his animals would get frisky and stay up all night after nibbling its berries. In the years since people figured out that coffee could affect us in similar ways, the plant has done a great deal for our species, an...
