A first-century sculpture from Homesteads on Hadrian’s Wall is a Roman-era image that refers to the local Celtic religion. These are three manifestations of the same god, Genii Cucullati, the hooded deities generally identified as dealing with healing, fertility, and the afterlife. Many people who spoke Indo-European were pre-occupied by the number three, and their deities frequently appear as trinities. Of all the European groups, this was most true of the Celts.
In a discussion of Classical myth and the oral traditions of Europe, it is important to understand something of the Indo-European languages. The exact nature of the Indo-European expansion is a matter of continuous debate. During the nineteenth century, linguists devoted a great deal of time exploring similarities in the group of languages known originally as Indo-Germanic. They quickly identified Latin (and its Romance-language descendants), Greek, Slavic, and the Germanic languages, including English, as part of a common linguistic family. It was easy to add to this Farsi, the language of Iran, and Sanskrit, the language of the ancient Aryan invaders of India. Indo-Germanic was, therefore, a large linguistic group that extended from India to the Germanic world. Later, it was clear that the Celtic languages of Ireland, Scotland, Wales, Cornwall, the Isle of Man, and Brittany were also part of the family, and so linguists changed the name to Indo-European to reflect the larger domain. Other languages have also been added, but this forms the basic core of what we now know as the Indo-European languages.
There is, however, controversy regarding what this linguistic distribution means. The original theory held that there was a prehistoric diaspora of the Indo-European people from central Eurasia sometime before or after the beginning of the second millennium BCE. These warrior herders presumably invaded various parts of Eurasia, conquering the local inhabitants and imposing their language and mythology wherever they went. This idea first became discredited for political reasons because Adolph Hitler exploited what many found to be a repugnant notion of racial superiority. In his mind, blond, blue-eyed Aryans demonstrated their superiority by subjugating “lesser peoples” in a distant past.
After World War II, many scholars began to question whether people were migrating or if the spread of Indo-European languages and oral traditions merely indicated the diffusion of language and folklore without the movement of people. The recent history of the English language demonstrates that language, free of people, can spread. When people from Japan and Thailand meet to discuss a business transaction, they communicate with a shared language, which is often English, and all of this occurs without anyone of English ancestry present. Similarly, Christianity conquered Europe and the New World without people from the Middle Eastern homeland migrating with it. Islam converted large parts of sub-Saharan Africa and Southeast Asia without the migration of Arabs, and Buddhism spread to China and Japan without the presence of people from India. Aspects of culture as important as language and religion can and do move independently of people. Still, sometimes people also move in large numbers, often with violent results. Europeans migrated to and conquered vast parts of the New World, Africa, and Australia, although with varying long-term effects. Arabs swept across North Africa. Germanic tribes moved into large parts of the Roman Empire, often imposing their language.
We may never know what the dispersion of Indo-European languages represented. It probably signified a combination of the spread of language and mythology and of people themselves. The number of people involved may have been limited in some areas and more plentiful in others. From a folklorist’s point of view, the significance of this diffusion resides in the fact that people who spoke Indo-European languages seemed also to share – if at times unevenly – a pantheon of gods and supernatural beings, the names of which are often linguistically related. In addition, there is a common heritage of folktales from India to Ireland that seems to underscore a mutual patrimony. Since oral traditions diffuse without the movement of actual people, the resolution of the question about the spread of Indo-European languages and its relationship to the dispersal of people is of lesser importance to a discussion of folklore.
Evidence suggests that Aphrodite, the beautiful goddess of love, Athena, the goddess of wisdom, and Hera, the goddess of motherhood, were on occasion regarded as manifestations of the same supernatural being. The problem for subsequent scribes was not unlike that faced by those who worked with the Christian concept of the Trinity, which maintains that the Father, the Son, and the Holy Spirit are three distinct and yet permanently-linked entities. A scribe attempting to address the subtleties of such a concept would need to choose between addressing the Trinity in superficially separate terms and dealing with the entwined nature of the more intricate concept of unity. Classical authors who dealt with their contemporary belief systems dropped the complexity for whatever reason.
Much later tradition describes St. Patrick as attempting to explain the subtleties of the Trinity by showing the Irish a shamrock - a plant with three leaves joined at the middle: three and yet one. It is absurd to imagine the pagan Irish unable to understand such a concept since their pantheon was filled with this sort of thing. In oral tradition, the emphasis lingers strongly to the present: Western Europeans and North Americans frequently insist that "things happen in threes." In Indo-European and Semitic folktales, repetition occurs in threes. This almost has the appearance of being universal, but there are important exceptions. Where there are three repetitions or three brothers in a European folktale, the story in India will feature four, in keeping with the importance of that number in the subcontinent. Similarly, various American Indian cultures feature four or five as the preferred number, and this manifests in its oral tradition. Danish folklorist, Axel Olrik, made the point that literature, with the need for great realism, has fallen away from this rule, leaving oral tradition as the original form of storytelling exhibiting this rigid approach to narrative.