In areas from north China northeastward and across the Bering Strait into North America, a particular type of microlithic "core tool" has been widely discovered. The further east one goes, the more recent the period in which this type of tool appears.
從中國的華北向東北延伸，通過白令海峽到達北美，都廣泛發現一種細石器工具﹘﹘扁體石核，越向東走，這種石核出現的時間離現代越近。