Besides Clovis, Eden, and Plainview, Alaska has provided cores that Nelson finds “identical in several respects with thousands of specimens found in the Gobi Desert.” He recognizes them as evidence of migration from Asia 9,000 to 12,000 years ago.[29] [Illustration: _A Gypsum Cave point. (After Roberts, 1940.)_] A New Point—and Sloths—in Gypsum Cave After the discovery of the Eden point, the next important development came in 1930 with M. R. Harrington’s excavation of Gypsum Cave, Nevada. Here he found the dung, hair, skin, and bones of the ground sloth in clear association with a wide variety of artifacts. Besides the sloth, there were fossils of camel and perhaps horse. Among the artifacts was a new type of diamond-shaped point, and—quite as remarkable—there were parts of painted dart shafts with the butts pitted for use with a spear-thrower. In addition to knives and oval scrapers, there were fire hearths. Gypsum man burned sloth dung as well as wood, and used torches. Harrington dated the culture at about 10,500 years ago. Radiocarbon dates from sloth dung six feet four inches deep averaged 10,455 ± 340 years.[30] Similar material closer to the surface recorded 8,527 ± 250 years.[31] Thus Gypsum seems to follow Folsom.[32] Such discoveries of the traces of early man in the United States and Canada spurred anthropologists to new work in the field, with the result that we now have over one hundred sites where a few of man’s bones or a host of his artifacts have been found with the fossils of bison, elephant, camel, horse, or sloth or in geological strata that date him close to the Great Ice Age and probably in it. Seven North American sites, and two in Middle America remain to be discussed. Some are outstanding in evidence of age. Old Lake and River Sites In 1934 and 1935 Mr. and Mrs. W. H. Campbell found traces of man along the beaches of vanished lakes in the southern California desert. At first Antevs believed that the lakes formed when the glaciers were melting away 20,000 to 25,000 years ago, but now he dates the artifacts and camp sites as less than 9,000 years old. At Lake Mohave, in the Campbells’ first year of work, they found only stone tools—Mohave and Silver Lake points—but in the Pinto Basin they came upon the bones of extinct mammals as well as artifacts.[33] Malcolm J. Rogers challenges the dating of Mohave and Pinto as “largely a matter of opinion,” and believes that “even approximate dates ... cannot be set.” In his own opinion, Pinto points—mixed with Gypsum in the same area—range only from 1,800 to 2,800 years ago. The Lake Mohave industry cannot begin, he maintains, earlier than 3,000 to 4,000 years ago.[34] In 1946, Robert F. Heizer and Edwin M. Lemert and later A. E. Treganza discovered in Topanga Canyon, north of Los Angeles, points and crude scrapers and choppers very like those at Lake Mohave and Gypsum Cave and also milling stones.[35] Lake Mohave artifacts have been found in northwestern Canada.[36]