Contact between religions is a lot like contact between languages. One way for two language communities to interact is through invasion. Conquests leave a relatively small number of invaders in control of the political and cultural institutions in the subjugated territory, and faced with the problem of how to talk to the conquered population. In the linguistic landscape of the invaded region, or of any region where a small group achieves dominance over a larger subordinate group through any means, the dominant group is said to form the superstrate, while the subjugated peoples form the substrate. It’s in the interests of the substrate population to be able to communicate with the new boss, and in the interests of the superstrate to be able to efficiently administer the conquered area. Interesting things often happen to the languages of both groups.
Sometimes the superstrate language replaces the substrate language with near totality, as Spanish, Portuguese and English have largely displaced the original languages of the Americas. In other cases, the substrate re-emerges as the language of learning and administration, perhaps in altered form, after decades or centuries have passed, as Middle English did after the Norman Conquest. For language families with a long history of expansion like Indo-European, the odd nature of insular Celtic or the characteristic features of Germanic have been explained with appeals to substrate effects. On the one hand this makes sense, because there were clearly people already living in the British Isles and Central Europe before the Celts and Teutons arrived. However, the nature of the substrate languages is all but unknown, so it’s difficult to make a solid argument that a substrate language left traces of itself. It’s easier to make a case for substrate or superstrate effects when both languages still exist. The Franks who replaced the Roman administration of Gaul lent their name to modern French, but within a few generations the language of the West Franconian elite was no longer a Germanic dialect but rather a form of Latin, although several Germanic words remained.
(The Book of Mormon seems to describe a classic substrate-superstrate situation, where the Nephite language and political system supplant the illiterate Mulekite rule. To a certain degree, the Book of Mormon before 3 Nephi is a history from the perspective of the victor. To what extent did Nephite interactions with other peoples result in, say, Helaman speaking a language as different from Hebrew as modern French is from Old Low Franconian? It’s impossible to know, but it should be added to the list of possibilities that can be contemplated.)
One of the important developments in medieval Christianity was in a sense a case of substrate effects. Christianity was spread to Germanic peoples from the second century onwards, first by contact with the Romans, then through Irish missionaries, finally by the Frankish nobility who wouldn’t take no for an answer from their subjects or their neighbors. By the ninth century, the Franks had achieved a substantial degree of influence on the Christian institutions of Europe. While the Germanic substrate religion had entirely disappeared, some have argued that the result of christianizing the Germans was a Germanicized Christianity, a religion that was strongly influenced by Germanic values and concepts. Sometimes the spread of religion works the other way: the first Visigothic Christians in the third century were converted from paganism to Arian Christianity through the example of their slaves who had been captured in Anatolia.
Itâ€™s not too hard to find substrate and superstrate effects in Mormon history, and maybe even in your own ward. Some have argued for a latent–substrate–Puritanism in the earliest Mormons. Others have observed that former Baptist preachers can give rocking good sermons. Wilfried has mentioned that the odd Dutch speech patterns of American missionaries come to be adopted by native members. As much as members of my German ward shy away from singing “O Savior, Thou who Wearest a Crown” with the remark “but that’s Lutheran,” I like to think that the area’s predominant religion and many members’ former church is behind the reverence with which the priesthood brethren reverently bear the implements of the sacrament out of the chapel at the close of the meeting while the congregation sits in contemplation. Church doctrine and organization are the same everywhere, but superstrate notions do not always prevail in determining how the members implement teachings and programs. Sometimes the substrate shows through.