Paleolithic archaeologists have employed expectations generated from models developed in evolutionary anthropology to aid in the investigation of the origins of high-fidelity cultural transmission. Based on the notion that copying error ought to yield high levels of between-group cultural variation under unbiased cultural transmission, archaeologists have interpreted ostensibly “lower-than-expected” levels of cultural variation among regional archaeological assemblages as evidence of widespread conformist biased transmission. But a closer inspection of cultural evolutionary theory suggests the expectation that unbiased transmission yields high between-group differentiation holds only for a narrow, idealized set of conditions that are likely to be violated in empirical cases. Additionally, it is unclear how or if this expectation translates to time-averaged assemblages of artifacts even under special conditions. I’ve developed a relatively simple agent-based model of cultural transmission in a structured population to improve our understanding of how cultural evolutionary forces affect between-group variation in a selectively neutral discrete trait under a wide range of conditions. My experimental design addresses how intergroup transmission and copying error affect regional cultural variation under four different mechanisms of cultural transmission (unbiased, vertical, conformist, or prestige biased) and two different models of copying error (finite or infinite variants). I quantify cultural differentiation not only between groups in a structured population but also between time-averaged assemblages of culture material. The results highlight three points: 1) there are many conditions—not just widespread conformity—in which one should expect relatively low variation among semi-, or even completely, isolated groups (and the archaeological assemblages they create through time) despite the effects of copying error, 2) the way in which intergroup transmission and copying error affect between-group (and between-assemblage) variation varies among cultural transmission mechanisms, and 3) time-averaging affects between-assemblage variation differently under different cultural transmission mechanisms. Considering these findings, I propose a list of questions one should answer before attempting to infer mechanisms of cultural transmission from time-averaged archaeological assemblages. Answers to these questions will help researchers better match expectations of regional cultural variation with the empirical case at hand.