In the United States, Leakey and his colleagues Miss Ruth De Ette Simpson and Dr Tom Clements have reported, in Science, the results of an excavation carried out in an old alluvial fan at the foot of the Calico Mountains near Yermo, Southern California. Work was carried out here for four seasons, and as a result more than 160 specimens, which Leakey and his colleagues regard as unquestionably human artifacts, were found in situ in an area of less than 25*25 feet. They can only be regarded as of human origin and thus represent the oldest known cultural material anywhere in the New World, since the deposit is dated, by geologists, between 35,000 and 100,000 years with 60,000-80,000 years. A number of American archaeologists who have knowledge of primitive cultures in Africa, Asia and Europe support Leakey and his colleagues' interpretation of these specimens as being of human origin, as do some British and French archaeologists.