elucidated by African archaeology at Olduvai, but meanwhile, in the early 20th century, the term "Pre-Acheulean" came into use in climatology. C.E.P, Brooks, a British climatologist working in the United States, used the term to describe a "chalky boulder clay" underlying a layer of gravel at Hoxne, central England, where Acheulean tools had been found. Whether any tools would be found in it and what type was not known. Hugo Obermaier, a contemporary German archaeologist working in Spain, quipped:Unfortunately, the stage of human industry which corresponds to these deposits cannot be positively identified. All we can say is that it is pre-Acheulean. This uncertainty was clarified by the subsequent excavations at Olduvai; nevertheless, the term is still in use for pre-Acheulean contexts, mainly across Eurasia, that are yet unspecified or uncertain but with the understanding that they are or will turn out to be pebble-tool. There are ample associations of Mode 2 with H. erectus in Eurasia. H. erectus – Mode 1 associations are scantier but they do exist, especially in the Far East. One strong piece of evidence prevents the conclusion that only H. erectus reached Eurasia: at Yiron, Israel, Mode 1 tools have been found dating to 2.4 mya, about 0.5 my earlier than the known H. erectus finds. If the date is correct, either another Hominan preceded H. erectus out of Africa or the earliest H. erectus has yet to be found. After the initial appearance at Gona in Ethiopia at 2.7 mya, pebble tools date from 2.0 mya at Sterkfontein, Member 5, South Africa, and from 1.8 mya at El Kherba, Algeria, North Africa. The manufacturers had already left pebble tools at Yiron, Israel, at 2.4 mya, Riwat, Pakistan, at 2.0 mya, and Renzidong, South China, at over 2 mya. The identification of a fossil skull at Mojokerta, Pernung Peninsula on Java, dated to 1.8 mya, as H. erectus, suggests that the African finds are not the earliest to be found in Africa, or that, in fact, erectus did not originate in Africa after all but on the plains of Asia. The outcome of the issue waits for more substantial evidence. Erectus was found also at Dmanisi, Georgia, from 1.75 mya in association with pebble tools. Pebble tools are found the latest first in southern Europe and then in northern. They begin in the open areas of Italy and Spain, the earliest dated to 1.6 mya