Chapter four of this book is adeptly entitled "The Geography of Language" and, of course, focuses on the languages of the world and how they are divided up geographically. This, of course, goes hand in hand with migration (discussed in chapter 3), so the beginning of this chapter pays close attention to that concept.
Next, there is a neat map of Africa in regards to how the ancient languages there spread over the millennia and how the Indo-European language diffused throughout those two continents. The "source" map of languages is incredibly telling with the small highlighted areas in Europe, Asia, and Africa being quite small while the diffusion over continents is quite vast.
What is more certain is that in later millennia, the diffusion of certain Indo-European languages--in particular Latin, English, and Russian--occurred in conjunction with the territorial spread of great political empires.
Therefore, chapter four now gets into how politics itself helped to mold languages. This is a good precursor to discuss what they describe as "Austronesian Diffusion" which is basically the languages of the Pacific Islands, how they differ, how they are the same, and how they traveled.
Probably the most interesting part of the chapter is the section called "Religion and Linguistic Mobility." Here the editors focus upon how Religion can shape a language and even a cultural identity.
Cultural interaction creates situations in which language is linked to a particular religious faith or denomination, a linkage that greatly heightens cultural identity.
The best example of this, says chapter four, is the connection between Arabic and the religion of Islam.
Next , the influence of habitat is discussed. It is described how habittat can definitely shape language. Why? Sometimes habitat actually has "physical barriers" that prevent the spread of language. The Alps in Europe are a good example of this kind of barrier. And finally, political habitat and borders are discussed in regards to how they shape language.
Toponyms are the last thing discussed in the chapter. These are simply stated as follows:
Toponym: a place-name, usually consisting of two parts, the generic and the specific.
The Human Mosaic makes a great point in that Toponyms can tell people a lot about the importance of geography and culture of a particular part of regional society.
Can it be a little longer please !!! I need at least 600 words