Understanding togetherness: Unravelling the evolutionary, developmental, and cultural foundation of human interaction

• Applicant: Raphaela Heesen, Ph.D.
• Subject Area: Evolution, Anthropology ; General, Cognitive and Mathematical Psychology ; Sensory and Behavioural Biology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550994438

Humans excel in colonizing the globe due to unique capacities for complex cooperative behavior and communication. Given the impact of hyper-cooperation on our species biological success and future on a finite planet, there is a pressing debate to better understand the evolutionary origins of this critical social adaptation. One theorized first step towards hyper-cooperation was the evolution of joint action - a form of social engagement that relies on the knowledge of acting together and normative obligations. Joint action origins were traditionally assessed in laboratory experiments, in which the cooperative abilities of human children and our closest ape relatives, chimpanzees, were compared based on their performance in social games with human experimenters. While these findings point to species differences, my own recent work has shown that, when apes interact with conspecifics in natural interactions, they exhibit remarkable similarities with humans in how they communicate to coordinate interactions. These findings raise questions about the ecological relevance of former studies, and thus the validity of existing evolutionary theories, warranting the need of new evidence from naturalistic settings. Adopting a naturalized approach, I will overcome this gap by providing a novel investigation of how humans and nonhuman primates (NHP) spontaneously collaborate with peers by means of bodily synchrony, emotion-sharing, and communicative signals. I propose a large-scale comparative examination of communicative and affective skills critical to human joint action: recipient-designed signals (Research Objective "RO"1), repair of misunderstandings (RO2), leave-taking to end interactions (RO3), and emotion-sharing (RO4). To assess the phylogenetic and convergent evolutionary origins of these skills, they will be compared between humans, chimpanzees, and Callitrichid monkeys, the latter living in cooperative breeding systems like us. To examine respective developmental origins in humans, these skills will be examined at age stages critical for joint action development (3y, 5y, 10y). To promote inclusion of non-WEIRD (Western, Educated, Industrialized, Rich, and Democratic) cultures, I will also examine variation in the four skills across German and Ugandan populations. Moreover, my project will go beyond previous method standards and a sole focus on cognition: By combining state-of-the art technologies like posture tracking and thermal imaging, I will provide a detailed quantification of fast-paced bodily movements and emotions in joint action. Consequently, my work will inform on ecologically meaningful variation in cooperative skills, and thus on the evolutionary, cultural, and developmental origins of human joint action. This will lay the groundworks for advanced evolutionary theories on how humans have (and do) become ultra-cooperative, leveraging unprecedented knowledge of the mechanisms and origins of our species’ most important social adaptation.

• DFG Programme: Independent Junior Research Groups