FURTHER DATA ABOUT VENOUS CHANNELS IN SOUTH-AFRICAN PLIOPLEISTOCENE HOMINIDS

Original data about venous channels in South African Plio-Pieistocene hominids are discussed. To assess possible changes in blood volume how of fossil hominids, we test whether dimensions of three extracranial venous foramina were different between Australopithecus africanus and Australopithecus (Paranthropus) robustus. Moreover, providing further data about the small sample of South African Plio-Pleistocene hominids , we also attempt to re-analyse the incidence of divided hypoglossal c anals and four emissary foramina in a very large sample of extant Afri can apes representing all ages, species and subspecies, in A. africanu s and in ''robust australopithecines''. Up to now. only very poor data on extracranial dimensions of venous foramina were available for foss il hominids. However, this topic provides interesting information abou t the modifications of volume flow during human evolution. Assuming th at in fossil hominids, as in humans, dimensions of condylar and mastoi d foramina, as well as those of jugular foramina, depended on volume f low through them, we conclude, first, that volume flow through interna l jugular veins was comparable in South African australopithecines, ex tant chimpanzees and humans, and second, that, in comparison with the errant less-encephalized chimpanzees (presumably reflecting the ancest ral condition), volume how was higher through condylar veins in A. (P. ) robustus. This increase was responsible for a significantly wearer a mount of blood drainage from the brain (and consequently an increased arterial blood supply). We support the view that encephalization was t he prevailing functional explanation for volume flow increase through condylar veins in A. (P.) robustus, in comparison with its ancestor wi th its presumably more ape-like degree of encephalization. Considering the incidence of emissary canals and foramina, significant difference s between A. africanus, ''robust australopithecines'' and all the exta nt African ape species, were tested statistically. Concerning the cond ylar canal, we did not find differences between ''robust australopithe cines'' and extant African apes. Concerning the incidence of divided h ypoglossal canals; mastoid canals, parietal and occipital foramina, no difference was found between extant African apes, A. africanus and '' robust australopithecines''. High frequencies of either condylar or ma stoid canals cannot be regarded as a ''pongid condition''. Moreover, w e did not find convincing data to support the hypothesis that mastoid emissary veins (partly representing a putative ''radiator'' for coolin g the brain) were selected in A. africanus, in comparison with ''robus t australopithecines''. (C) 1997 Academic Press Limited.