Compared to the complex use of human language, the way animals communicate with each other appears quite simple. How our language evolved from such a simple system, remains unclear. Researchers from the Max Planck Institutes for Evolutionary Anthropology (MPI-EVA) and for Cognitive and Brain Sciences (MPI-CBS) in Leipzig, Germany, and the CNRS Institute for Cognitive Sciences in Bron, Lyon, France, recorded thousands of vocalisations from wild chimpanzees in Taï, Ivory Coast. They found that the animals produced hundreds of different vocal sequences containing up to ten different call types. The order of calls in these sequences followed some rules, and calls were associated with each other in a structured manner. The researchers will now investigate if this structure may constitute a step towards human syntax and if chimpanzees use these sequences to communicate a wider range of meanings in their complex social environment.