Modern views on the evolution of emotional expressions and the role of anatomical facial structures in this process

Abstract

Introduction. The study of emotional facial expressions is currently gaining momentum, attracting researchers from diverse scientific disciplines. We suppose that this surge in interest can be attributed, in part, to the rapid advancement of digital technologies, particularly artificial neural networks, which are increasingly capable of recognizing and encoding facial expressions. The power of these technologies to analyze faces and emotional states is widely discussed in the media and popular culture, prompting scientists to approach the topic with both responsibility and maximum caution in judgements.

Results. Important to mention immediately, that in the modern literature on the anatomy of facial expression, there is no consensus on the number and composition of muscles involved in the expression of emotions on the human face. Different authors indicate a different number of muscles involved in emotional facial expressions. Such discrepancies may cause significant confusion, especially for researchers who are not specialists in human anatomy. This article presents an analytical review based on anatomical sources and the Facial Action Coding System (FACS), a leading anatomically validated technique for recognizing and classifying facial expressions. Alongside the anatomy of the muscular system, we explore the characteristics of the related neural structures. To provide readers with a comprehensive understanding of facial communication, we delve into the history of its study and present an evolutionary journey tracing the development of the human face, the emergence, and evolution of facial expressions in phylogeny.

Conclusion. Facial expressions of emotion are the result of a long evolutionary process, closely interrelated with the development of the nervous system and social organization. Based on the most comprehensive data, the muscular system underlying human emotional expressions is more complex than typically suggested in anatomical classifications. Overall, it comprises 26 paired and one single muscle, many of which are further subdivided into smaller parts with distinct expressive functions. We believe that this article will help to systematize modern data on the anatomy of human facial expressions. © 2025. This work is licensed under a CC BY 4.0 license

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