During the 1970s, ethologists at the German Max Planck Institute for Behavioral Physiology in Seewiesen started a series of research projects at several regional kindergartens in search of natural predispositions in human behavior. This so-called “Kindergarten Project” became one of the pillars of research activity at the newly founded Forschungsstelle für Humanethologie (Research Center for Human Ethology) where Irenäus Eibl-Eibesfeldt and a team of researchers set out to explore new fields of research for the discipline of ethology. Taking the research project conducted by biologist Barbara Hold on ranking behavior among kindergarten children as a vantage point, this paper explores the shift in ethology from animal to human behavior which occurred during the 1960s and 1970s. It analyzes how human ethologists coped with the methodological, conceptual, and ethico-political challenges which arose from crossing the human-animal divide. This article thus sheds light on the hitherto unwritten history of human ethology as it was developed at the MPI since the late 1960s.