Populations of orangutans living in different jungle habitats develop and transmit distinct behaviors in a manner akin to human cultural transmission, according to a new Current Biology study that considered the effects of geography, genetics, and environment on the behavioral differences. Researchers have previously shown that populations of the red apes living in the jungles of Borneo and Sumatra perform certain behaviors—such as kissing into a clenched fist like a trumpet or using a branch as a fly swatter—in different ways. But it has been unclear whether the variation among populations was due to social learning, indicating culture, as opposed to variation in the environment or genetics. Now, researchers from the University of Zurich have shown, using thousands of hours of behavioral observation data combined with genetic profiling and scores of environmental and ecological measurements, that cultural transmission must be at play in the patchwork of behavioral differences seen across the species' range. "The novelty of our study is that, thanks to the unprecedented size of our dataset, we were the first to gauge the influence genetics and environmental factors have on the different behavioral patterns among the orangutan populations," study co-author Carel van Schaik told Wired.
Previous research has demonstrated a similar phenomenon in wild populations of chimpanzees. Together, the results suggest that the tendency to develop and share particular behaviors in a group of apes may have roots in evolutionary ancestors shared with humans. "The cultural interpretation of the behavioral diversity also holds for orangutans—and in exactly the same way as we would expect for human culture," Michael Krützen, who was first author on the study, told Wired.