<P> By voluntary agreement, archaeologists respect the decisions of the Pan-African Congress of Prehistory, which meets every four years to resolve archaeological business brought before it . Delegates are actually international; the organization takes its name from the topic . Louis Leakey hosted the first one in Nairobi in 1947 . It adopted Goodwin and Lowe's 3 - stage system at that time, the stages to be called Early, Middle and Later . </P> <P> The problem of the transitions in archaeology is a branch of the general philosophic continuity problem, which examines how discrete objects of any sort that are contiguous in any way can be presumed to have a relationship of any sort . In archaeology, the relationship is one of causality . If Period B can be presumed to descend from Period A, there must be a boundary between A and B, the A--B boundary . The problem is in the nature of this boundary . If there is no distinct boundary, then the population of A suddenly stopped using the customs characteristic of A and suddenly started using those of B, an unlikely scenario in the process of evolution . More realistically, a distinct border period, the A / B transition, existed, in which the customs of A were gradually dropped and those of B acquired . If transitions do not exist, then there is no proof of any continuity between A and B . </P> <P> The Stone Age of Europe is characteristically in deficit of known transitions . The 19th and early 20th - century innovators of the modern three - age system recognized the problem of the initial transition, the "gap" between the Paleolithic and the Neolithic . Louis Leakey provided something of an answer by proving that man evolved in Africa . The Stone Age must have begun there to be carried repeatedly to Europe by migrant populations . The different phases of the Stone Age thus could appear there without transitions . The burden on African archaeologists became all the greater, because now they must find the missing transitions in Africa . The problem is difficult and ongoing . </P> <P> After its adoption by the First Pan African Congress in 1947, the Three - Stage Chronology was amended by the Third Congress in 1955 to include a First Intermediate Period between Early and Middle, to encompass the Fauresmith and Sangoan technologies, and the Second Intermediate Period between Middle and Later, to encompass the Magosian technology and others . The chronologic basis for definition was entirely relative . With the arrival of scientific means of finding an absolute chronology, the two intermediates turned out to be will - of - the - wisps . They were in fact Middle and Lower Paleolithic . Fauresmith is now considered to be a facies of Acheulean, while Sangoan is a facies of Lupemban . Magosian is "an artificial mix of two different periods ." </P>

What were the effects of agriculture on stone age society