Stone-Age technology. As a description of people living today, the term Stone Age is controversial. The Association of Social Anthropologists discourages this use, asserting:To describe any living group as 'primitive' or 'Stone Age' inevitably implies that they are living representatives of some earlier stage of human development that the majority of humankind has left behind. Three-stage system In the 1920s, South African archaeologists organizing the stone tool collections of that country observed that they did not fit the newly detailed Three-Age System. In the words of J. Desmond Clark, It was early realized that the threefold division of culture into Stone, Bronze and Iron Ages adopted in the nineteenth century for Europe had no validity in Africa outside the Nile valley. Consequently, they proposed a new system for Africa, the Three-stage System. Clark regarded the Three-age System as valid for North Africa; in sub-Saharan Africa, the Three-stage System was best. In practice, the failure of African archaeologists either to keep this distinction in mind, or to explain which one they mean, contributes to the considerable equivocation already present in the literature. There are in effect two Stone Ages, one part of the Three-age and the other constituting the Three-stage. They refer to one and the same artifacts and the same technologies, but vary by locality and time. The three-stage system was proposed in 1929 by Astley John Hilary Goodwin, a professional archaeologist, and Clarence van Riet Lowe, a civil engineer and amateur archaeologist, in an article titled "Stone Age Cultures of South Africa" in the journal Annals of the South African Museum. By then, the dates of the Early Stone Age, or Paleolithic, and Late Stone Age, or Neolithic (neo = new), were fairly solid and were regarded by Goodwin as absolute. He therefore proposed a relative chronology of periods with floating dates, to be called the Earlier and Later Stone Age. The Middle Stone Age would not change its name, but it would not mean Mesolithic. The duo thus reinvented the Stone Age. In Sub-Saharan Africa, however, iron-working technologies were either invented independently or came across the Sahara from the north (see iron metallurgy in Africa). The Neolithic was characterized primarily by herding societies rather than large agricultural societies, and although there was copper metallurgy in Africa as well as bronze smelting, archaeologists do not currently recognize a separate Copper Age or Bronze Age. Moreover, the technologies included in