Introducing chapter seven ("On the Races of Man"), Darwin wrote "It is not my intention here to describe the several so-called races of men; but to inquire what is the value of the differences between them under a classificatory point of view, and how they have originated." In answering the question of whether the races should rank as varieties of the same species or count as different species, Darwin discussed arguments which could support the idea that human races were distinct species. This included the geographical distribution of mammal groups which was correlated with the distribution of human races, and the finding of Henry Denny that different species of lice affected different races differently.