To understand the evolution of craniofacial asymmetry within the Perissodini tribe, a group of scale-eating fish found in Lake Tanganyika, we performed shape analysis on their craniofacial architecture, and applied a simple lever model to measure asymmetry in lower-jaw mechanics. We found that craniofacial asymmetries were the consequence of sided differences in size and shape of craniofacial elements, and that sided differences in shape predict the lateralization of force and speed of the lower jaw in derived species. Quantitative Trait Locus analysis in Lake Malawi cichlids identified a single locus of major effect for jaw laterality, the first genetic marker for handedness in an antisymmetric trait. Studying the evolution of laterality in Perissodus and ultimately identifying the genetic factors that contribute to the asymmetric development of skeletal structures will shed light on the evolutionary and clinical consequences of vertebrate laterality
