We know that the connection is easily severed, thanks to the genetic experiments called immigration and conquest, in which children get their grammars from the brains of people other than their parents. Needless to say, the children of immigrants learn a language, even one separated from their parents’ language by the deepest historical roots, without any disadvantage compared to age-mates who come from long lineages of the language’s speakers. Correlations between genes and languages are thus so crude that they are measurable only at the level of superphyla and aboriginal races.
