The craniofacial morphology of the genus Homo shows a strong trend of decreasing robusticity during the Middle and Late Pleistocene.
Groening, F., Fagan, M., & O'Higgins, P. (2009). Variation in Mandibular Morphology Within Late Homo and its Relevance to Masticatory Load Resistance. Journal of Vertebrate Paleontology, 29(Suppl. 1), 109A. https://doi.org/10.1080/02724634.2009.10411818