On Abstinence from Killing Animals: History of Sacrificial Acts

Originally, then, sacrifices to the gods were made with crops. In time we came to neglect holiness, and when crops were lacking and through the dearth of lawful food people took to eating each other’s flesh, then, imploring the divine power with many prayers, they first offered the gods sacrifice from among themselves, not only consecrating to the gods whatever was finest among them, but taking in addition others of the race who were not among the best. From then until now, it is not only in Arcadia at the Lykaia and in Carthage for Kronos that everyone engages in public human sacrifice, but periodically, in remembrance of the custom, they stain altars with the blood of their own kind, even though holiness, among them, excludes from the rites by lustral water and by proclamation anyone responsible for the blood of a friend. [...]