were almost wholly lacking in early North American archaeology. There was a nearly universal belief that the native inhabitants had arrived in the Western Hemisphere only within the last two or three millennia and that their cultures had undergone little or no significant advance during the subsequent interval. At the same time, however, ethnographers could recognize the enormous diversity of culture exhibited by present-day Indians in different parts of the continent, and it was expected, correctly, that the same diversity would be encountered in the archaeological record. As a result, culture classification in North America from the beginning came to emphasize geographical rather than chronological variation.

If the informing framework for Old World cultural classification was the theory of social evolution, the informing framework for New World classification was the culture-area concept. In simplest terms, this concept involves the recognition that cultures in different regions show a high degree of similarity to one another but differ from those in neighboring regions as a result partly of historical diffusion but mostly of adaptation to differing environmental resources. Culture-area theory, unlike early evolutionary theory, places a heavy emphasis on specialized adaptation.

American prehistorians had the enormous advantage, which the Europeans lacked, of observing the living, immediate descendants of the peoples whom they were studying archaeologically. Inevitably, American archaeology developed and has retained a close alliance with ethnology, and the basic framework followed in classifying prehistoric cultures reflects, at least in a general way, the model employed in classifying the living Indian cultures. This culture-area model was developed initially by ethnologists at the Smithsonian Institution at the end of the nineteenth century. The earliest formulation, published in 1896, envisioned sixteen culture areas in North and Central America: Northwest Coast, Southwest, Great Plains, and so on (Mason 1896). The culture areas were differentiated most importantly by modes of subsistence (maize agriculture, forest hunting, fishing, collecting, etc.) but also by commonalities of technology, housing, social organization, and religion.

Archaeologists, assuming that the remains they dug were immediately ancestral to living Indian cultures, tended for a time to take the culture-area theory as a given. Moreover, their excavations for a long time failed to uncover any conspicuously stratified sites or any evidence of genuinely primitive Paleolithic-type cultures, thus seemingly confirming the general belief in a recent migration of the Indians from the Old World. As investigations progressed, however, two things became apparent: first, there was considerable diversity among the prehistoric cultures even within certain culture areas, and second, there had indeed been substantial developmental change in many of the prehistoric cultures. This realization led, in the 1920s, to a widespread recognition of the need for a classification of the prehistoric American cultures that would be independent of existing ethnographic classifications.

The first Pecos Conference, held in New Mexico in 1927, marks the beginning of formal classification in American prehistory. The conferees agreed to divide the prehistoric Pueblo culture (now called Anasazi) into seven developmental stages, each marked by distinctive pottery types, house types, and settlement patterns as well as certain other cultural criteria (Kidder 1927). Although this division was, strictly speaking, a periodization rather than a classification, it set a pattern of systematization that was soon widely copied in other parts of North America. Within a very few years, several other cultures had been defined and periodized not only in the Southwest but in the Midwest, Northeast, and other areas. Within two decades, systematic cultural classifications had been developed for nearly the whole of North America, as well as for parts of Central and South America (Martin, Quimby, and Collier 1947). Cultures and their subdivisions were defined on the basis of a wide variety of culture traits, artifactual and architectural, but projectile points were always treated as primary in the definition of preceramic cultures while pottery types played the same role in the later cultures.

The proliferation of named cultures led, at