Black English Vernacular

Black English" can refer to two different language varieties: (1) the type of English used by people of African and Caribbean descent who live in Britain; (2) the language of African-Americans in the United States. This is usually called Black English Vernacular or BEV for short. "Black English" in both senses has its historical roots in a creolised form of English which dates back to the time of slavery. Creoles are languages which evolve from Pidgins when the pidgins become first languages for some or all of their speakers. Black English Vernacular has a somewhat different history (and is a different language) from British Black English."

Ebonics pronunciation includes features like the omission of the final consonant in words like 'past' (pas' ) and 'hand' (han'), the pronunciation of the th in 'bath' as t (bat) or f (baf), and the pronunciation of the vowel in words like 'my' and 'ride' as a long ah (mah, rahd). Some of these occur in vernacular white English, too, especially in the South, but in general they occur more frequently in Ebonics. Some Ebonics pronunciations are more unique, for instance, dropping b, d, or g at the beginning of auxiliary verbs like 'don't' and 'gonna', yielding Ah 'on know for "I don't know" and ama do it for "I'm going to do it."

Here is will show some of the theories used when researching into Black English Vernacular:

The Anglicist Hypothesis was set forth by dialectogists including Hans Kurath (1949) and Raveb McDavid (McDavid and McDavid 1951) in the mid-twentieth century.  It was the reigning hypothesis for until the mid-1960s.
According to the Anglicist Hypothesis, development of African-American Vernacular English followed the same path as the language of other immigrants would.  The theory suggests that when slaves were brought to the U.S. from Africa, they initially spoke a number of different languages.  However, by being exposed to English, they began to learn it.  As slaves had children, their native languages were preserved less and less.  This patter is visible in the modern day as well -- many children of immigrants speak their parents' native language barely or not at all, and their children will not be exposed to it at all.  In this way, it is thought that through a couple of generations the slaves' native languages all but died out in the United States.  They were replaced by the regional or social dialect of English that surrounded them at the time. 

The Creolist Hypothesis was the first major alternative to the Anglicist Hypothesis.  This hypothesis suggests that African-American Vernacular English developed from a creole language that was a result of the early contact between Africans and Europeans. 
A creole is a language that develops due to contact between two groups who do not know each other's language.  This happens in two steps.  First, a pidgin is created.  A pidgin is a pseudo-language, usually developed for the purpose of allowing groups with different languages to trade, that includes a combination of both languages.  Pidgins are usually narrow, specialized, and not really grammatical.  However, it is possible for a pidgin to continue to develop into a functional language.  This usually happens with the next generation, who grow up hearing the pidgin and learn it from an early age.  The resulting language is known as a creole.  A creole is a fully-formed language that does follow grammar rules.

The Neo-Anglicist Hypothesis maintains that the earlier African-American Vernacular originated based on the British dialects that were brought to the U.S.  However, in contrast with the Anglicist Hypothesis, the Neo-Anglicists do not maintain that modern features of AAVE can be traced to British dialects.  Instead, they believe that at some point, the African-American Vernacular diverged from the other dialects and became more diverse.  This started a process of further diversion, reinforced by the solidification and unification of the African-American community.  This more insular community of practice resulted in further innovation of features that were unique to AAVE and the African-American community, rather than just holdovers from its history with British English dialects.  

The Substrate Hypothesis suggests that while earlier African-American Vernacular dialects may have incorporated many features of other regional dialects due to contact with them, it has always differentiated itself in virtue of a strong substrate effect.
In linguistics, a substrate effect occurs when a language is influenced continually by its exposure to or contact with another language, even if this language no longer transfers features to the other language or is no longer in contact with it.  Even after the contact has ceased, it can still have an effect on the way the first language develops later on.
Substrate Hypothesists believe that AAVE has always differentiated itself via the substrate effect, due to possible early contact with creole speakers, even if they themselves never developed a full-fledged creole.  It is believed that contact with creole speakers during the passage of slaves from Africa to North America could have been sufficient to influence the later development of AAVE, resulting in its differentiation from other American dialects of the same geographical area and social stratum.