A stretch of floodplain in northwestern Oklahoma, already known for its profusion of prehistoric hunting sites, has turned up new find: a scatter of butchered bison bones dating back nearly 11,500 years -- extending the evidence of bison hunting in the area by centuries, archaeologists say... Together, these artifacts lend new depth to the already ample record of ancient hunts -- including three bison-kill sites that are even older -- in a region of the southern Plains known as the Beaver River complex... The latest find was made on a narrow bench of land between two arroyos by Carlson's colleague,...