Hidden by rocks near a waterhole in Australia’s desert interior an Aboriginal woman and her children catch their first sight of the shockingly large animal of which they have previously only heard: the newcomer’s kangaroo. Thousands of kilometres to the west and high in southern Africa’s mountains a shaman completes the painting of an animal that does not exist, horned at the front, bushy tail at the rear, a composite of two species, one long familiar, the other new. Across the Atlantic Ocean on the grasslands of Patagonia the burial of an Aónik’enk leader is in its final stages, four of his favourite possessions killed above the grave to ensure his swift passage to the afterlife. To the north in what Americans of European descent call New Mexico, Diné warriors chant the sacred songs that ensure their pursuers will not catch them and that they will return safely home. And on the wintry plains of what is not yet Alberta, Siksikáwa hunters charge into one of the last bison herds they will harvest before the snows bring this year’s hunting to an end. Two things unite these very different scenes. First, though we cannot be sure, the historical, ethnographic, and archaeological sources on which they are based allow for them all happening on precisely the same day, sometime in the 1860s. Second, all concern people’s relationship with one and the same animal—pindi nanto, karkan, kawoi, ∤íí’, ponokáómita·wa—the animal that English speakers know as ‘horse’. And that simple fact provides the basis for this book. For, before 1492, horses were confined to the Old World—Europe, Asia, and Africa north of the tropical rainforests and a line reaching east through South Sudan, Ethiopia, and Somalia to the sea. They were wholly unknown in Australasia, the Americas, or southern Africa. As a result, the relationships implied by the vignettes I have just sketched, as well as those involving Indigenous populations in Colombia, Venezuela, Brazil, Paraguay, Uruguay, Chile, Mexico, South Africa, and New Zealand, evolved quickly. And they were still evolving when these societies were finally overwhelmed by European colonization.