Researchers have successfully modified a standardized system for analyzing facial expressions to include bonobos, our closest living relatives alongside chimpanzees. Led by an international team of scientists from Leipzig University and the Max Planck Institute for Evolutionary Anthropology, the study expands the Chimpanzee Facial Action Coding System (ChimpFACS) to another species closely related to humans and chimpanzees, bonobos.

The research confirms that bonobos exhibit a repertoire of 28 distinct facial movements, including 22 specific muscle actions, showcasing facial expression capabilities similar to their chimpanzee counterparts. This discovery offers new insights into how these endangered great apes communicate and convey emotions.

Lead researcher Dr. Catia Correia-Caeiro explains, "This adaptation of ChimpFACS for bonobos bridges a crucial gap in our ability to study facial expressions across various primate species. It enables us to systematically compare facial movements among humans, chimpanzees, and bonobos, shedding light on the evolution of facial communication."

The study indicates that although bonobos display fewer facial movements than humans, they share all the facial movements observed in chimpanzees. This similarity underscores the significance of facial communication in the social interactions of both species.

Aside from academic research, the new coding system has practical implications. Dr. Correia-Caeiro notes, "This tool will be particularly beneficial for evaluating the well-being of bonobos in human care. By enhancing our understanding of their facial expressions, we can more accurately assess their emotional states and overall welfare."

The research is a collaborative effort involving scientists from institutions in Germany, Switzerland, France, the United States, and the United Kingdom, including the Berlin Zoo and Harvard University.

About the Research

The study builds on the well-established Facial Action Coding System (FACS), initially designed for humans and previously adapted for nine other species. This expansion to encompass bonobos establishes a standardized approach for measuring and comparing facial movements across different primate species.