Cultural macroevolution and the transmission of traits

Cultural traits are distributed across human societies in a patterned way. Study of the mechanisms whereby cultural traits persist and change over time is key to understanding human cultural diversity. For more than a century, a central question has engaged anthropologists interested in the study of cultural trait variation: What is the source of cultural variation? More precisely, are cultural traits transmitted primarily from ancestral to descendant populations (vertical transmission) or between contemporary, typically neighboring populations (horizontal transmission), or do they emerge as independent innovations? While debates among unilineal evolutionists and diffusionists have long since faded, there is still much uncertainty about how traits are transmitted at this macroevolutionary level, as well as about the implications of these transmission patterns for testing hypotheses regarding the adaptive function of particular cultural traits across human populations.