Cultural Evolution in Non-Human Animals

“Culture” is generally regarded as a population’s shared array of traditions, transmitted between individuals by processes of social learning, and which may persist from one generation to later ones. If we consider genetic material to provide the primary system of inheritance in living things, then social learning—learning from others—provides a second inheritance system in those species of animals that have the cognitive capacity to learn in this way. Once it was thought that cultural traditions inherited in this way were unique to, and defining of, our own species. This view was challenged by research arising particularly in the middle of the 20th century, which revealed evidence of the spread of innovations in the behavior of nonhuman species, generating traditions that passed from one generation to the next. Early examples included regional birdsong dialects and novel foraging techniques in Japanese macaque monkeys. Research over the last seventy years or so has accumulated a wealth of evidence that animal traditions exist in many aspects of behavior, from migration to mate choice and predator avoidance, and in numerous taxa including fish, birds, and mammals. Social learning has also been well documented in insects, although the existence of traditions in the wild remains less clear. Once such a second inheritance system does emerge, supporting the transmission of behavioral traditions, the potential exists for a second system of evolution—cultural evolution—which can be defined most simply as changes in culture over time. As in the case of organic evolution based on genetic inheritance, imperfect copying and sampling error may be sufficient to cause evolutionary changes, known as drift. Alternatively, some innovations may prove to be more adaptive than others, in which case we can expect the essential Darwinian processes of variation, selection, and inheritance to generate some directional cultural evolution. Both drift and Darwinian evolution have long been evident in human cultural evolution, but evidence has begun to accumulate for them also in nonhuman species. Humans additionally display cumulative culture, in which some form of progress builds cumulatively on the achievements of previous generations. Examples are legion, from the evolution of wheeled vehicles to languages and religions. A currently contentious issue is whether such cumulative cultural evolution is unique to our species, or is shared in some ways with others. Other current areas of uncertainty include which cognitive mechanisms underlie animal social learning and whether the precision of animal social learning can support long-lasting traditions; the degree to which animal cultures extend broadly enough across behavioral repertoires, or deeply enough in the complexity of individual traits, to be usefully compared to those of humans; and whether culture creates selection pressures that are long lasting enough to shape animals’ genomes. In general, while it is very clear that human culture is more extensive than in any other species, there is less agreement about which qualitative differences in psychological and cultural processes are responsible for this gulf.