cristine_h_legare's picture
Associate Professor, Department of Psychology, The University of Texas at Austin; Director, Cognition, Culture, and Development Lab
Cumulative Culture

Over the 7 million years since humans and chimpanzees shared a common ancestor, the inventory of human tools has gone from a handful of stone implements to a technological repertoire capable of replicating DNA, splitting atoms, and interplanetary travel. In the same evolutionary timespan, the chimpanzee toolkit has remained relatively rudimentary. It was "tool innovation"—constructing new tools or using old tools in new ways—that proved crucial in driving increasing technological complexity over the course of human history.

How can we explain this wide divergence in technological complexity between such closely related primate species? One possibility is that humans are unique among primate species in our capacity to innovate. If so, we might expect that innovation would be early-developing like walking or language acquisition. And yet there is little evidence for precocious innovation in early childhood. Although young children are inquisitive and keen to explore the world around them, they are astonishingly poor at solitary tool innovation. New Caledonian crows and great apes outperform young children in tool innovation tasks. This is particularly striking given the dazzling technological and social innovations associated with human culture. How does a species with offspring so bad at innovation become so good at it? 

Technological complexity is the outcome of our species’ remarkable capacity for cumulative culture; innovations build on each other and are progressively incorporated into a population's stock of skills and knowledge, generating ever more sophisticated repertoires. Innovation is necessary to ensure cultural and individual adaptation to novel and changing challenges, as humans spread to every corner of the planet. Cultural evolution makes individuals more innovative by allowing for the accumulation of prefabricated solutions to problems that can be recombined to create new technologies. The subcomponents of technology are typically too complex for individuals to develop from scratch. The cultural inheritance of the technologies of previous generations allows for the explosive growth of cultural complexity.

Children are cultural novices. Much of their time is spent trying to become like those around them—to do what they do, speak like they do, play and reason like they do. Their motivation to learn from, and imitate, others allows children to benefit from and build upon cumulative cultural transmission. Cumulative culture requires the high fidelity transmission of two qualitatively different abilities—instrumental skills (e.g., how to keep warm during winter) and social conventions (e.g., how to perform a ceremonial dance). Children acquire these skills through high fidelity imitation and behavioral conformity. These abilities afford the rapid acquisition of behavior more complex than could ever otherwise be learned exclusively through individual discovery or trial-and-error learning.

Children often copy when uncertain. This proclivity is enormously useful given that a vast amount of behavior that we engage in is opaque from the perspective of physical causality. High-fidelity imitation is an adaptive human strategy facilitating more rapid social learning of instrumental skills than would be possible if copying required a full causal representation of an event. So adaptive, in fact, that it is often employed at the expense of efficiency, as seen when kids "over-imitate" behavior that is not causally relevant to accomplishing a particular task.

The unique demands of acquiring instrumental skills and social conventions such as rituals provide insight into when children imitate, when they innovate, and to what degree. Instrumental behavior is outcome-oriented. Innovation often improves the efficiency of solving defined problems. When learning instrumental skills, with an increase in experience, high-fidelity imitation decreases. In contrast, conventional behavior is process-oriented. The goals are affiliation and group inclusion. When learning social conventions, imitative fidelity stays high, regardless of experience, and innovation stays low. Indeed, innovation impedes learning well-prescribed social conventions. Imitation and innovation work in tandem, deployed at different times for different purposes, to support learning group-specific skills and practices. The distinct goals of instrumental skills and social conventions drive cumulative culture and provide insight into human cognitive architecture.

Cumulative culture affords collective insights of previous generations to be harnessed for future discoveries in ways that are more powerful than the solitary brainpower of even the most intelligent individuals. Our capacity to build upon the innovations of others within and across generations drives our technological success. The capacity for cumulative culture has set our genus Homo on an evolutionary pathway remarkably distinct from the one traversed by all other species.