Well, American Dialects Have Been Studied For

This African American Vernacular English Shares Most Of Its Grammar And Vocabulary With Other Dialects Of English. But It Is Distinct In Many Ways, And It Is More Different From Standard English Than Any Other Dialect Spoken In Continental North America.

However, Research In The Years That Followed Found That In Many Of Its Important Features, African American Vernacular English Was Becoming Not Less, But More Different From Other Dialects.

An Important Aspect Of The Current Situation Is The Strong Social Reaction Against Suggestions That The Home Language Of African American Children Be Used In The First Steps Of Learning To Read And Write.

Well, American Dialects Have Been Studied For A Hundred Years Or So.

It Appears That The Present-day Form Of African American English Is Not The Inheritance Of The Period Of Slavery, But The Creation Of The Second Half Of The 20th Century.