In his 1863 book, Journal of the Discovery of the Source of the Nile, he showed a strange fixation with an extended clan of leaders in what is now present-day Rwanda. These people-they called themselves Tutsis-measured their wealth in cows, drank milk, ate beef, and seemed to be taller and have slightly more angular noses than their subjects, who fed their families by growing cassavas, sweet potatoes, and other vegetables. Speke theorized that they were actually a lost tribe of Christians who had migrated from the deserts of the Middle East and were therefore the carriers of a noble line of blood. The Hutu-what Speke called the “curly-head, flab-nosed, pouch-mouthed negro”-was a different story. The name itself means “one who works, ” and Speke thought there was a divine purpose behind the differences in lifestyle. Those who grew crops, he said, were probably the distant descendants of Noah’s son Ham, who according to the ninth chapter of Genesis had committed the sin of looking at his father lying naked in a tent when he, Noah, was drunk on homemade wine. For this transgression Noah cursed his son Ham’s descendants for all time.“The lowest of slaves will he be to his brothers, ” said the man who had captained the ark through the floodwaters. And, to Speke’s way of thinking, these poor lowborns had obviously found their way to exile in Central Africa and had reproduced themselves by the millions. The Hutus were part of that accursed lot, and this explained their generally subservient role to the cattle-owning Tutsis, even though the two groups of people looked quite similar on the surface.

All of this is, of course, total European foolishness, but what came to be called the “Hamitic hypothesis” carried a surprising amount of weight in the late nineteenth century, just as the great powers were preparing to carve up Africa into colonies. These ideas about race were to become more than fanciful stories told over port at the Royal Geographic Society but an actual template for governing us. The real origin of Rwanda ’s class system had almost nothing to do with physical characteristics. It was much more banal than anything the European gentlemen explorers had been able to imagine.