John McWhorter has argued that programs to revive indigenous languages will almost never be very effective because of the practical difficulties involved. He also argues that the death of a language does not necessarily mean the death of a culture. Indigenous expression is still possible even when the original language has disappeared, as with Native American groups and as evidenced by the vitality of black American culture in the United States, among people who speak not Yoruba but English. He argues that language death is, ironically, a sign of hitherto isolated peoples migrating and sharing space: “To maintain distinct languages across generations happens only amidst unusually tenacious self-isolation—such as that of the Amish—or brutal segregation”.