How did Clark Wissler explain the diffusion of cultural traits?

Clark Wissler explained the diffusion of cultural traits by identifying both the mechanisms that facilitate their spread and the factors that act as barriers. He proposed that innovations typically diffuse outward in all directions from their point of origin.1

Wissler argued that cultural traits spread most readily among groups sharing the same "culture pattern," while traits originating outside that pattern are less likely to be adopted, suggesting that culture itself can slow or prevent diffusion. Additionally, he identified environmental obstacles, such as geographic barriers like the Rocky Mountains, which could physically prevent the movement of resources or traits between groups.1

Based on these observations, Wissler developed the age-area hypothesis, which posits that because traits tend to diffuse equally in all directions, those with the widest geographic distribution are generally the oldest. While this hypothesis was later criticized for being overly simplistic, Wissler’s broader work on culture areas remains a foundational framework for understanding how cultural complexes relate to environmental zones and patterns of innovation.123