Greek and Roman societies developed, in their separate ways and at different times, a very refined sense of their own identity and could articulate a clear sense of where the borders of their geographical and conceptual worlds were positioned (although in practice there was a large and diverse set of cultures and communities within these boundaries). A major concern particularly of Greek writers in the fifth century BC, after the Persian wars, was understanding what united the Greeks and what separated them from barbarians: aside from the language barrier, which defines the notion of the barbaros, religious customs were seen as something which all Greeks had in common. Similarly, Roman writers at times of conquest, when the borders of the Roman Empire were being pushed back, were constantly re-evaluating the identity of the people who lived at and beyond the frontiers of the empire. Writing within living memory of the Persian wars, Herodotus spends much of his nine-book history describing the geography and people outside the Greek world. His accounts of their treatment of animals — however reliable the details — again tell us as much or more about the sensibilities of the writer’s own society and that of his readership as it does about the exotic practices he describes. Egypt was a source of constant fascination for Greek and Roman writers. Herodotus describes Egyptian sacrificial ritual, and its details were presumably intended to be compared with the Greek practice with which his audience would have been very familiar.