The power of caring touch: from survival to prosocial cooperation.

Cooperation is a pivotal biological phenomenon that occurs in diverse forms. In species that engage in helping, individuals vary in the time they spend together and the degree of their physical proximity, which affects the extent of physical touch between individuals. Here, we propose that touch activates a hormonal feedback loop that supports bond formation and maintenance in mating, parenting, and social contexts. Notably, extended parenting is essential for the emergence of enduring bonds and the development of the prosocial mindset that fosters forms of cooperation with delayed benefits. We incorporate these ideas into the caring-touch hypothesis (CT-H), which emphasizes the role of oxytocin-vasotocin hormones, touch, and enduring bonds in the evolution of different forms of cooperation.