This talk discusses a new book—The Perfection of Nature: Animals, Breeding, and Race in the Renaissance (The University of Chicago Press 2022)—which offers a history of how Renaissance Italy and the Spanish empire were shaped by a lingering fascination with breeding. While one strand of the Renaissance celebrated a liberal view of human potential, another limited it by biology, reducing man to beast and prince to stud. Combining population genetic and bioarcheological findings with research in Italian, Latin, Spanish, and Nahuatl, this history follows domesticated animals—including horses, dogs, turkeys, and llamas—to show parallel cultures of animal breeding in Europe and the Americas. Over the course of their collision in the sixteenth century, the dangerous idea of controlled reproduction was brought to life again and again, and a rich, complex, and ever-shifting language of race and breeding was born. The Perfection of Nature excavates historical moments of ambiguity between humanity and animality to reveal that early modern personhood was often culturally conditional rather than legally, biologically, or theologically fated.