I am hoping to share some ideas and insights garnered through years of study as to the dispersal of the different language groups. Of course my experience is limited, but not, I trust, without value.
It is too easy, or at least has been in the past, to mistake a culture from the appearance of its pottery or its fashion in cutlery. Identifying a new fashion historians and archaeologists have been lead to define this as a new culture and not simply a new style of making or decorating pots and clothes. Fashions spread, and none more quickly than those of a new and useful technology. Yet the people who adopt them may be people of a different language family who accept the new technique into their culture and even some of the language associated with it.
It is from this standpoint that I have made my investigations, tracing where possible, movements of technology and skills, through language as well as through artefacts. Language can be surprisingly slow to change, particularly among trades and coteries. Jargon displays familiarity with a subject and keeps others in their place.