Page "Penutian languages" Paragraph 55

Even where genetic relationship is clearly indicated ... the evidence of diffusion of traits from neighboring tribes, related or not, is seen on every hand.

This makes the task of determining the validity of the various alleged Hokan languages and the various alleged Penutian languages all the more difficult point up once again that diffusional studies are just as important for prehistory as genetic studies and what is even more in need of emphasis, it points up the desirability of pursuing diffusional studies along with genetic studies.

This is nowhere more necessary than in the case of the Hokan and Penutian languages wherever they may be found, but particularly in California where they may very well have existed side by side for many millennia .< cite >( Haas 1976: 359 )</ cite >