Researchers have successfully adapted a standardized system for analyzing facial expressions to include bonobos, our closest living relatives alongside chimpanzees. The study, led by an international team of scientists from multiple institutions including Leipzig University and the Max Planck Institute for Evolutionary Anthropology, extends the Chimpanzee Facial Action Coding System (ChimpFACS) to another species closely related to humans and chimpanzees, bonobos.
The research confirms that bonobos possess a repertoire of 28 distinct facial movements, including 22 specific muscle actions, demonstrating facial expression capabilities comparable to their chimpanzee cousins. This finding provides new tools for understanding how these endangered great apes communicate and express themselves.
"This adaptation of ChimpFACS for bonobos fills an important gap in our ability to study facial expressions across different primate species," explains lead researcher Dr. Catia Correia-Caeiro. "We can now systematically compare facial movements between humans, chimpanzees, and bonobos, offering insights into the evolution of facial communication."
The study revealed that while bonobos show fewer facial movements than humans, they share all the facial movements observed in chimpanzees. This similarity suggests the importance of facial communication in both species' social interactions.
The new coding system has practical applications beyond academic research. "This tool will be particularly valuable for assessing the welfare of bonobos in human care," notes Dr. Correia-Caeiro. "By better understanding their facial expressions, we can more accurately gauge their emotional states and well-being."
The research represents a collaboration between scientists from institutions across 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 widely recognized Facial Action Coding System (FACS), originally developed for humans and previously adapted for nine other species. This extension to include bonobos provides a standardized method for measuring and comparing facial movements across different primate species.
