Pachyosteosclerosis suggests archaic Homo frequently collected sessile littoral foods.
Fossil skeletons of Homo erectus and related specimens typically had heavy cranial and postcranial bones, and it has been hypothesised that these represent adaptations, or are responses, to various physical activities such as endurance running, heavy exertion, and/or aggressive behavior. According to the comparative biological data, however, skeletons that show a combination of disproportionally large diameters, extremely compact bone cortex, and very narrow medullary canals are associated with aquatic or semi-aquatic tetrapods that wade, and/or dive for sessile foods such as hard-shelled invertebrates in shallow waters. These so-called pachyosteosclerotic bones are less supple and more brittle than non-pachyosteosclerotic bones, and marine biologists agree that they function as hydrostatic ballast for buoyancy control. This paper discusses the possibility that heavy skeletons in archaic Homo might be associated with part-time collection of sessile foods in shallow waters.