In the last third of the nineteenth century an older model of folk migration was challenged and ultimately gave way to a new model of racial invasion. Where the first was associated with comparative philology and an evolutionary account of social institutions, the latter was associated with physiological ideas of race and a quasi-diffusionist idea of institutions. The debate began over the newly discovered pre-Roman prehistory of the British Isles, but was most bitterly fought over ethnological and agrarian interpretations of the Anglo-Saxon conquest. Resolution of the debate saw a redefinition of the nature and scope of English history.