He assumes the pre-existence of pre-Indo-European languages linked to the archeological Linear Pottery culture and to a family of languages featuring complex verbs, of which the Northwest Caucasian languages might have been the sole survivors.
In its mature phase, the Jastorf area proper in northern Lower Saxony (Lüneburger Heide, lower Elbe) can be contrasted with the so-called Nienburg (also Harpstedt-Nienburg) group to the west, situated along the Aller and the middle Weser, bordering the Nordwestblock separating it from the La Tène culture proper farther south.