Which feature does H. heidelbergensis lack compared to modern humans?

Homo heidelbergensis is often noted for its similarities to both earlier hominins and modern humans, but one significant feature that distinguishes it from contemporary Homo sapiens is the lack of a clear chin. Modern humans possess a well-defined chin that contributes to the shape of the lower face and reflects adaptations associated with changes in diet and social behavior. In contrast, H. heidelbergensis has a more receded, less prominent jawline without the distinct chin observed in modern humans, indicating a different evolutionary stage in the development of facial features.

The other features mentioned do not effectively differentiate H. heidelbergensis from modern humans in the same way. For instance, H. heidelbergensis had a relatively large brain size, which was advanced for its time, although not as large as that of modern humans. It also walked upright, sharing this fundamental characteristic with modern humans, as both belong to the hominin lineage that developed bipedalism. Similarly, the robust mandible of H. heidelbergensis reflects its adaptation to a tough diet but does not serve as a distinguishing factor since modern humans show considerable variation in jaw robustness as well. Thus, the definitive feature that H. heidelbergensis lacks compared to modern humans