question: When and how did greek/roman mythology slowly shift from a religion to mythology
comment: It happened as the people of those regions converted to other religions, primarily when they converted to Christianity.
passages: After Christian theology was accepted by the Roman Empire, promoted by St. Augustine in the 5th century, Christian mythology began to predominate the Roman Empire. Later the theology was carried north by Charlemagne and the Frankish people, and Christian themes began to weave into the framework of European mythologies. The pre-Christian Germanic and Celtic mythology that were native to the tribes of Northern Europe were denounced and submerged, while saint myths, Mary stories, Crusade myths, and other Christian myths took their place. However, pre-Christian myths never went entirely away, they mingled with the (Roman Catholic) Christian framework to form new stories, like myths of the mythological kings and saints and miracles, for example (Eliade 1963:162-181). Stories such as that of Beowulf and Icelandic, Norse, and Germanic sagas were reinterpreted somewhat, and given Christian meanings. The legend of King Arthur and the quest for the Holy Grail is a striking example. The thrust of incorporation took on one of two directions. When Christianity was on the advance, pagan myths were Christianized; when it was in retreat, Bible stories and Christian saints lost their mythological importance to the culture.
   While Roman mythology may lack a body of divine narratives as extensive as that found in Greek literature, Romulus and Remus suckling the she-wolf is as famous as any image from Greek mythology except for the Trojan Horse. Because Latin literature was more widely known in Europe throughout the Middle Ages and into the Renaissance, the interpretations of Greek myths by the Romans often had a greater influence on narrative and pictorial representations of "classical mythology" than Greek sources. In particular, the versions of Greek myths in Ovid's "Metamorphoses", written during the reign of Augustus, came to be regarded as canonical.
   Because ritual played the central role in Roman religion that myth did for the Greeks, it is sometimes doubted that the Romans had much of a native mythology. This perception is a product of Romanticism and the classical scholarship of the 19th century, which valued Greek civilization as more "authentically creative." From the Renaissance to the 18th century, however, Roman myths were an inspiration particularly for European painting. The Roman tradition is rich in historical myths, or legends, concerning the foundation and rise of the city. These narratives focus on human actors, with only occasional intervention from deities but a pervasive sense of divinely ordered destiny. In Rome's earliest period, history and myth have a mutual and complementary relationship. As T. P. Wiseman notes:
   Section::::Historical development.:Middle Ages.
  
  According to Mircea Eliade, the Middle Ages witnessed "an upwelling of mythical thought" in which each social group had its own "mythological traditions". Often a profession had its own "origin myth" which established models for members of the profession to imitate; for example, the knights tried to imitate Lancelot or Parsifal. The medieval trouveres developed a "mythology of woman and Love" which incorporated Christian elements but, in some cases, ran contrary to official church teaching.
   Mythology based on (though, not identical to) the pre-Christian traditions was still common place knowledge in Celtic-speaking cultures in the 19th century. In the Celtic Revival, such survivals were collected and edited, thus becoming a literary tradition, which in turn influenced modern mainstream "Celticity".
   Thanks largely to Seznec, it is widely understood that the Olympian gods, and the earlier spirits of field and spring, did not die with the advent of Christianity, but lived on. His work traces the process in which they were already transformed during Late Antiquity, whether embedded within history as transfigured former human beings in the Euhemerist view that was embraced by Christian apologists ("interpretatio christiana"), or given planetary roles as astral divinities in the worldview of astrology and magic or allegorized as moral emblems. They surviving in pictorial and in literary traditions and among the common people went underground to feature in folk culture, took on strange new guises and were transformed in various ways, their myths recast to suit some of the mythic saints of Late Antiquity. Their imagery permeated Medieval intellectual and emotional life. The transformed mythology re-emerged in the iconography of the early Tuscan Renaissance, with new attributes that the ancients had never imagined, and enjoyed tremendous renewed popularity during the Renaissance.
   The mythology largely survived and was added to in order to form the later Roman mythology. The Greeks and Romans had been literate societies, and much mythology, although initially shared orally, was written down in the forms of epic poetry (such as the "Iliad", the "Odyssey" and the "Argonautica") and plays (such as Euripides' "The Bacchae" and Aristophanes' "The Frogs"). The mythology became popular in Christian post-Renaissance Europe, where it was often used as a basis for the works of artists like Botticelli, Michelangelo and Rubens.
  
  Section::::Beliefs.:Morality.
   In Ancient Roman times, a new Roman mythology was born through syncretization of numerous Greek and other foreign gods. This occurred because the Romans had little mythology of their own, and inheritance of the Greek mythological tradition caused the major Roman gods to adopt characteristics of their Greek equivalents. The gods Zeus and Jupiter are an example of this mythological overlap. In addition to the combination of the two mythological traditions, the association of the Romans with eastern religions led to further syncretizations. For instance, the cult of Sun was introduced in Rome after Aurelian's successful campaigns in Syria. The Asiatic divinities Mithras (that is to say, the Sun) and Ba'al were combined with Apollo and Helios into one Sol Invictus, with conglomerated rites and compound attributes. Apollo might be increasingly identified in religion with Helios or even Dionysus, but texts retelling his myths seldom reflected such developments. The traditional literary mythology was increasingly dissociated from actual religious practice. The worship of Sol as special protector of the emperors and of the empire remained the chief imperial religion until it was replaced by Christianity.
   Section::::Greek and Roman conceptions of myth.:Philosophy and myth.
  
  After the rise of philosophy, history, prose and rationalism in the late 5th century BC, the fate of myth became uncertain, and mythological genealogies gave place to a conception of history which tried to exclude the supernatural (such as the Thucydidean history). While poets and dramatists were reworking the myths, Greek historians and philosophers were beginning to criticize them.
   In 170 AD, the Temple of Demeter was sacked by the Sarmatians but was rebuilt by Marcus Aurelius. Aurelius was then allowed to become the only lay person ever to enter the anaktoron. As Christianity gained in popularity in the 4th and 5th centuries, Eleusis's prestige began to fade. The last pagan emperor of Rome, Julian, reigned from 361 to 363 after about fifty years of Christian rule. Julian attempted to restore the Eleusinian Mysteries and was the last emperor to be initiated into them.
   Section::::Use by governments and public institutions.
  
  Roman conquerors allowed the incorporation of existing Greek mythological figures such as Zeus into their coinage in places like Phrygia, in order to "augment the fame" of the locality, while "creating a stronger civil identity" without "advertising" the imposition of Roman culture.
   The spread of Greek literature, mythology and philosophy offered Roman poets and antiquarians a model for the interpretation of Rome's festivals and rituals, and the embellishment of its mythology. Ennius translated the work of Graeco-Sicilian Euhemerus, who explained the genesis of the gods as apotheosized mortals. In the last century of the Republic, Epicurean and particularly Stoic interpretations were a preoccupation of the literate elite, most of whom held – or had held – high office and traditional Roman priesthoods; notably, Scaevola and the polymath Varro. For Varro – well versed in Euhemerus' theory – popular religious observance was based on a necessary fiction; what the people believed was not itself the truth, but their observance led them to as much higher truth as their limited capacity could deal with. Whereas in popular belief deities held power over mortal lives, the skeptic might say that mortal devotion had made gods of mortals, and these same gods were only sustained by devotion and cult.
   Section::::Religion and myth.:Foreign gods.
   The record of the history of the development of a culture and society is embodied in its mythology. For example, the Bible describes the evolution of the Judeo-Christian concept of God from the time when the Jews were in Babylon and the god they worshiped corresponded to a local tribal god, to when the concept became that of a world savior as a result of the Hebrews becoming a major force in the East Mediterranean region. The geographic context of a specific mythology also plays a role in its evolution. The physical scope of Biblical mythology was limited to the general area of the Middle East but in other parts of the world, Chinese and Aztec religions and cultures emerged as separate and distinct belief systems. When different cultures expand their spheres of influence they eventually come into contact with each other, and the outcome of the collision, be it conquest, subjugation, or amalgamation, will be evident in the resultant mythology.
   Section::::Greek and Roman conceptions of myth.:Syncretizing trends.
   Syncretized versions form the classical tradition of mythography, and by the time of the influential Renaissance mythographer Natalis Comes (16th century), few if any distinctions were made between Greek and Roman myths. The myths as they appear in popular culture of the 20th and 21st centuries often have only a tangential relation to the stories as told in ancient Greek and Latin literature.
  
  Section::::See also.
  
  Section::::See also.:Related topics.
  
  BULLET::::- Chariot clock
  
  BULLET::::- Classical tradition
  
  BULLET::::- Classics
  
  BULLET::::- Greco-Roman world
  
  BULLET::::- Greek mythology in western art and literature
  
  BULLET::::- LGBT themes in classical mythology
   The Pastoral Epistles contain denunciations of "myths" ("muthoi"). This may indicate that Rabbinic or Gnostic mythology was popular among the early Christians to whom the epistles were written and that the epistles' author was attempting to resist that mythology.
  
  The Sibylline oracles contain predictions that the dead Roman Emperor Nero, infamous for his persecutions, would return one day as an Antichrist-like figure. According to Bernard McGinn, these parts of the oracles were probably written by a Christian and incorporated "mythological language" in describing Nero's return.
  
  Section::::Historical development.
  
  Section::::Historical development.:From Roman Empire to Europe.
   Section::::Mythical themes and types.:Transference of evil.:Atonement in canonical scripture.
  
  Paul's theological writings lay out the basic framework of the atonement doctrine in the New Testament. However, Paul's letters contain relatively little mythology (narrative). The majority of narratives in the New Testament are in the Gospels and the Book of Revelation.
   During the Hellenistic period, mythology took on the prestige of elite knowledge that marks its possessors as belonging to a certain class. At the same time, the skeptical turn of the Classical age became even more pronounced. Greek mythographer Euhemerus established the tradition of seeking an actual historical basis for mythical beings and events. Although his original work ("Sacred Scriptures") is lost, much is known about it from what is recorded by Diodorus and Lactantius.
   Narratives of divine activity played a more important role in the system of Greek religious belief than among the Romans, for whom ritual and cult were primary. Although Roman religion did not have a basis in scriptures and exegesis, priestly literature was one of the earliest written forms of Latin prose. The books "(libri)" and commentaries "(commentarii)" of the College of Pontiffs and of the augurs contained religious procedures, prayers, and rulings and opinions on points of religious law. Although at least some of this archived material was available for consultation by the Roman senate, it was often "occultum genus litterarum", an arcane form of literature to which by definition only priests had access. Prophecies pertaining to world history and to Rome's destiny turn up fortuitously at critical junctures in history, discovered suddenly in the nebulous Sibylline books, which Tarquin the Proud (according to legend) purchased in the late 6th century BC from the Cumaean Sibyl. Some aspects of archaic Roman religion survived in the lost theological works of the 1st-century BC scholar Varro, known through other classical and Christian authors.
   The Latin term was then adopted in Middle French as "mythologie". Whether from French or Latin usage, English adopted the word "mythology" in the fifteenth century, at first in the sense 'the exposition of a myth or myths; the interpretation of fables; a book of such expositions'. The word is first attested in John Lydgate's "Troy Book" of c. 1425.
   Some well-known historical polytheistic pantheons include the Sumerian gods and the Egyptian gods, and the classical-attested pantheon which includes the ancient Greek religion and Roman religion. Post-classical polytheistic religions include Norse Æsir and Vanir, the Yoruba Orisha, the Aztec gods, and many others. Today, most historical polytheistic religions are referred to as "mythology", though the stories cultures tell about their gods should be distinguished from their worship or religious practice. For instance deities portrayed in conflict in mythology would still be worshipped sometimes in the same temple side by side, illustrating the distinction in the devotees mind between the myth and the reality. Scholars such as Jaan Puhvel, J. P. Mallory, and Douglas Q. Adams have reconstructed aspects of the ancient Proto-Indo-European religion, from which the religions of the various Indo-European peoples derive, and that this religion was an essentially naturalist numenistic religion. An example of a religious notion from this shared past is the concept of "*dyēus", which is attested in several distinct religious systems.
   Syncretism was common during the Hellenistic period, with rulers regularly identifying local deities in various parts of their domains with the relevant god or goddess of the Greek Pantheon, as a means of increasing the cohesion of the Kingdom. This practice was accepted in most locations, but vehemently rejected by the Jews who considered the identification of Yahwe with the Greek Zeus as the worst of blasphemy. The Roman Empire continued this practice - first by the identification of traditional Roman deities with Greek ones, producing a single Graeco-Roman Pantheon and then identifying members of that pantheon with the local deities of various Roman provinces. An undeclared form of Syncretism was the transfer of many attributes of the goddess Isis - whose worship was widespread in the Later Roman Empire - to the Christian Virgin Mary. Some religious movements have embraced overt syncretism, such as the case of melding Shintō beliefs into Buddhism or the amalgamation of Germanic and Celtic pagan views into Christianity during its spread into Gaul, the British Isles, Germany, and Scandinavia. In later times, Christian missionaries in North America identified Manitou - the spiritual and fundamental life force in the traditional beliefs of the Algonquian groups - with the God of Christianity. Similar identifications were made by missionaries at other locations in the Americas and Africa, whenever encountering a local belief in a Supreme God or Supreme Spirit of some kind. 
   Old Norse mythological stories survived in oral culture for at least two centuries, to be recorded in the 13th century. How this mythology was passed down is unclear; it is possible that pockets of pagans retained their belief system throughout the 11th and 12th centuries, or that it had survived as a cultural artefact passed down by Christians who retained the stories while rejecting any literal belief in them. The historian Judith Jesch suggested that following Christianisation, there remained a "cultural paganism", the re-use of pre-Christian myth "in certain cultural and social contexts" that are officially Christian. For instance, Old Norse mythological themes and motifs appear in poetry composed for the court of Cnut the Great, an eleventh-century Christian Anglo-Scandinavian king.
   At a "Consultation on the Relationship Between the Wesleyan Tradition
  
  and the Natural Sciences" in Kansas City, Missouri, on October 19, 1991, Dennis Bratcher presented a discussion of the adaptation of Near Eastern mythical thought by the Israelites. Bratcher argued that the Old Testament absorbed Near Eastern pagan mythology (although he drew a sharp distinction between the literally-interpreted myths of the Near Eastern pagans and the "mythopoetic" use of imagery from pagan myths by the Hebrews). During this presentation, he gave the following disclaimer:
  