In East Africa, particularly at Olduvai Gorge, there have been defined two stone artifact industries, first appearing in the archaeological record about 1,500,000 years ago, which are said to represent two distinct cultural traditions possibly produced by two different hominid taxa (Leakey 1971, 1976). These industries are the Acheulian and the Developed Oldowan. The problem is to determine whether two cultural traditions did indeed exist during this time period. This is an important question in terms of our concepts both of human biological evolution and of the antiquity of sociocultural diversification and the emergence of ethnic groups. The assumption that patterns of artifact variability express social group identity is here being tested. The following is a report of the results of a study of four lithic assemblages from Bed II, Olduvai Gorge, and a recently collected assemblage from Sterkfontein, the well-known australopithecine cave site in South Africa.' Because of limitations of space, only bifaces will be considered. The exclusion of data on the other artifact types is not critical for three reasons: (1) In her most recent paper, Leakey (1976) states that the principal difference between the Acheulian and the Developed Oldowan is in biface morphology and technology of manufacture. (2) The main focus here is on methodology. (3) Data concerning other artifact types has been or will be presented elsewhere (Stiles 1977).