THE M-OBTURATOR INTERNUS SULCUS ON MIDDLE AND LATE PLEISTOCENE HUMAN ISCHIA

Recent human ischia and those of Middle and Late Pleistocene hominids exhibit variation in the cranio-caudal location of the sulcus for the internal obturator muscle as it rounds the ischium through the lesser sciatic notch, from being fully cranial of the ischial tuberosity, to bordering the tuberosity, to crossing the superior tuberosity. Among t wo recent human samples, all three forms exist, with the cranial posit ion of the sulcus being more common in a 20th century Euroamerican sam ple whereas the intermediate one predominates in a horticultural late prehistoric Amerindian sample. The available Pleistocene Homo fossil r emains exhibit the full range of variation with no one form being domi nant in Middle Pleistocene archaic humans and Middle Paleolithic late archaic and early modern humans. It is only within the Upper Paleolith ic that the cranial and intermediate locations for the sulcus become p redominant. These patterns therefore indicate that it is inappropriate to use this feature for distinguishing later Pleistocene hominid grou ps. (C) 1996 Wiley-Liss, Inc.