Glacial maximums occurred around 14,000, 30,000, 42,000, and 55,000 years ago, with a land bridge available for periods of from about 5,000 to 10,000 years during each maximum ....
... Another aspect of the paleoenvironment is climatic variation due to topography and proximity to oceans. Climatic extremes are buffered in coastal areas by the warmer temperatures and sheer mass of the ocean, and these areas are not subject to the marked seasonality of continental climates. Rogers et al. (1992:291) write, "the coast would provide the pathway of least technological resistance to Ice Age people.... it would be the likely route of earliest entrance." Evidence of possible Ice Age migrations along the coast would have been impacted by rising sea levels, so this hypothesis cannot be easily tested archaeologically. ...
.. Bluefish Caves, Yukon, contains cultural materials, including lithic artifacts, bone alteration from butchering, bone tools and examples of bone reduction by flaking (Cinq-Mars and Morlan 1999:203). A mammoth bone flake and its core were studied, and Cinq-Mars and Morlan (1999:205-206) concluded that the bone evidences butcher marks and fresh-state fracture, and that the flake was reduced bifacially and diagonally in a step-by-step ordered sequence. The bone collagen and flake were AMS dated to an average age of 23,500 B.P. (Cinq-Mars and Morlan 1999:205). The radiocarbon dates from Bluefish Caves are considered reliable. The relation between the age of the bones and the time of their use as artifacts is questioned by Late-Entry advocates (Hoffecker, et al. 1993:50). ...
... Early Upper Paleolithic sites in southern Siberia, found below 55 degrees latitude and dated from 42,000 to 30,000 B.P., correspond to the Malokheta interstade, a relatively warm interval in the mid-Upper Pleistocene (Goebel 1999:213). ...
... The Beringian Tradition represents the original peopling of Beringia and all the Paleolithic sites in the time frame from 35,000 to 9,500 B.P. (West 1981, 1996:549). Mochanov defined, principally from sites on the Aldan River, a variant of the Siberian Upper Paleolithic tradition, the Diuktai culture, which he views as dominating all of eastern Siberia during the Late Pleistocene (Dumond 1980:988). Mochanov (1978:65) interprets the roots of the Diuktai complex as going back to the Levalloiso-Aucheulean cultural stratum in Asia.
The Diuktai Cave research delineated northeast Asia’s characteristic core-and-blade and biface industry in context with late Pleistocene megafauna. Diuktai Cave produced numerous flaked tools, including bifacial willow-leaf and subtriangular spearheads and oval knives (Mochanov 1980:122). The Diuktai Culture, a culture of hunters of mammoth, woolly rhinoceros, bison, horse, musk oxen and reindeer, is characterized by bifacial, willow-leaf, lancet-shaped, and subtriangular flint spearheads, as well as oval and semilunar knives, accompanied by end scrapers, burins, choppers, mammoth tusk spearheads, bone needles, wedge-shaped cores, and flint blade points (Mochanov 1980:123).
The Diuktai Culture existed in northeast Asia from 35,000 to 10,500 B.P. (Ikawa-Smith 1982:25). Mochanov includes Hokkaido and Sakhalin Islands in the east Asian Diuktai Tradition. The Diuktai variant is represented at Angara, Amur, Indigirka, Kolyma, Kamchatka, Kukhtui, as well as other sites in Asia from the southern Urals to Mongolia and China, in Japan, and in North America (Mochanov 1978a:65).
The most ancient Diuktai Culture sites on the Aldan River (UST-Mil 2 and Ikhine) date to the base of the Upper Paleolithic, near 35,000 B.P. (West 1996:543). ... -
http://jqjacobs.net/anthro/paleoamerican_origins.html