Human fathers exhibit hormonal shifts in testosterone, prolactin, and oxytocin, enabling flexible responses to parenting. In species with costly paternal care, these shifts balance mating and parenting efforts, suggesting evolved neuroendocrine capacities that support fatherhood. Today, fathers collaborate with mothers worldwide, though their roles vary across cultures and family systems, much as they likely did evolutionarily. Using research from the Philippines, Congo-Brazzaville, and the U.S., alongside cross-cultural data, this talk examines how men's hormonal physiology adapts to parenthood and influences family behaviors and bonds within diverse ecological and cultural contexts. Recorded on 02/14/2025. (#40387)