American archaeologists who founded the culture-history paradigm early in the 20th century held a view of the evolution of cultures commensurate with Darwin's notions of continuous, gradual change. Initially, in their view, artifacts varied continuously across space and through time. This materialist metaphysic was, however, short-lived. Its fall from favor began in the 1920s, when it was noted that cultural evolution was reticulate whereas biological evolution was only branching. When it was argued in the 1940s that cultures were, after all, not organisms and that inanimate objects did not interbreed, any hope of adopting a Darwinian version of evolution in archaeology was abandoned. Rather, archaeologists adopted cultural evolutionism founded by Herbert Spencer in the 19th century and popularized by Leslie White in the 20th century. Franz Boas and his students flatly rejected this version in part because of its essentialist metaphysic. A. L. Kroeber had some significant insights into how to construct historical lineages, but he and his contemporaries did not know how to implement Darwin's version of evolutionism in anthropology and archaeology. Archaeologists of the 1950s thus came to view culture change largely in terms of discontinuous stages. Such a view gained legitimacy because biologists in the 1950s claimed the evolution of cultures was unlike the evolution of organisms. After some forty years, it is time to try a Darwinian version of evolution.