Following the conquest of Algiers and its surrounding territory by the French army in 1830, officers noted an abundance of standing stones in this region of North Africa. Although they attracted considerably less attention among their cohort than more familiar Roman monuments such as triumphal arches and bridges, these prehistoric remains were similar to formations found in Brittany and other parts of France. The first effort to document these remains occurred in 1863, when Laurent-Charles Féraud, a French army interpreter, recorded thousands of dolmens and stone formations south-west of Constantine. Alleging that these constructions were Gallic, Féraud hypothesized the close affinity of the French, who claimed descent from the ancient Gauls, with the early inhabitants of North Africa. After Féraud's claims met with scepticism among many prehistorians, French scholars argued that these remains were constructed by the ancestors of the Berbers (Kabyles in contemporary parlance), whom they hypothesized had been dominated by a blond race of European origin. Using craniometric statistics of human remains found in the vicinity of the standing stones to propose a genealogy of the Kabyles, French administrators in Algeria thereafter suggested that their mixed origins allowed them to adapt more easily than the Arab population to French colonial governance. This case study at the intersection of prehistoric archaeology, ancient history and craniology exposes how genealogical (and racial) classification made signal contributions to French colonial ideology and policy between the 1860s and 1880s.