The tribes Europeans encountered in their colonial ventures in Africa, South Asia, the Pacific, and the Americas were at first assumed to have existed for a long time. They often claimed antiquity for themselves. But many tribes are now believed to have been transient political communities of the historical moment. Like the Ojibwa, some might have crystallized only after contact with European agents who wanted to deal with bounded groups to facilitate the negotiation of territorial treaties. And the same critical attitude toward bounded tribal territories is applied to European history. Ancient European tribal identities — Celt, Scythians, Cimbri, Teoton, and Pict — are now frequently seen as convenient names for chamelon-like political alliances that had no true ethnic identity, or as brief ethnic phenomena that were unable to persist for any length of time, or even as entirely imaginary later inventions.
That is from David W. Anthony’s The Horse The Wheel and Language: How Bronze-Age Riders from the Eurasian Steppe Shaped the Modern World. In particular this book focuses on the origin of the Indo-European language group and the relationship between archeology and linguistics. He is also skeptical of Jared Diamond’s well-known thesis that early Europe had much diffusion of innovation in the East-West direction. Recommended.