This article presents a theory of the perception of hybrids, resulting from cross-breeding natural animals that pertain to different species and of children parented by couples with a mixed ethnic or racial background. The theory states that natural living beings, including humans, are perceived as possessing a deeply ingrained characteristic that is called ‘essence’ or ‘blood’ or ‘genes’ in everyday discourse and that uniquely determines their category membership. If, by whatever means, the genes or essences of two animals of different species are combined in a hybrid, the two incompatible essences collapse, leaving the hybrid in a state of non-identity and non-belonging. People despise this state and reject the hybrid (Study 1). This devaluation effect holds with cross-kind hybrids and with hybrids that arise from genetically combining animals from incompatible habitats across three cultures: Austria, India and Japan (Study 2). In the social world, groups and ethnic or racial categories frequently are essentialized in an analogue way. When people with an essentialist mindset judge ethnically or racially mixed offspring, they perceive a collapse of ethnic or racial essence and, consequently, denigrate these children, as compared to children from ‘pure’ in-group or out-group parents (Study 3). The findings are discussed in terms of the widespread ‘yuck factor’ against genetically modified animals, in terms of the cultural concepts of monstrosity and of racism and prejudice.