The lack of bone morphological markers associated with the human control of wild animals has prevented the documentation of incipient animal domestication in archaeology. Here, we assess whether direct environmental changes (i.e. mobility reduction) could immediately affect ontogenetic changes in long bone structure, providing a skeletal marker of early domestication. We relied on a wild boar experimental model, analysing 24 wild-born specimens raised in captivity from 6 months to 2 years old. The shaft cortical thickness of their humerus was measured using a 3D morphometric mapping approach and compared with 23 free-ranging wild boars and 22 pigs from different breeds, taking into account sex, mass and muscle force differences. In wild boars we found that captivity induced an increase in cortical bone volume and muscle force, and a topographic change of cortical thickness associated with muscular expression along a phenotypic trajectory that differed from the divergence induced by selective breeding. These results provide an experimental proof of concept that changes in locomotor behaviour and selective breeding might be inferred from long bones morphology in the fossil and archaeological record. These trends need to be explored in the archaeological record and further studies are required to explore the developmental changes behind these plastic responses. Exploring the process of domestication as an integration of animals into human society provides a unique insight into one of the key steps in Homo sapiens evolution, at the root of its global impact over the biosphere 1 and species evolution 2. However, documenting this process, as an intensification of the relationship between humans and animals in archaeology 3 , is challenging 4,5. One of the main issues is that no relevant methodological approach has been able to capture this elusive process. Bioarchaeologists have relied on a morphological 'syndrome of OPEN 1 Archéozoologie, Archéobotanique: Sociétés, Pratiques et Environnements, UMR 7209,