The discovery of bison bones in Peoria County proves the animals were in Illinois about 1,700 years earlier than previously thought, according to scientists. Radiocarbon dating confirmed a group of eight bison died at a site along the Illinois River around 265 B.C., said Alan Harn, an archaeologist with Dickson Mounds Museum. Until the dating tests, scientists did not have evidence of bison in Illinois before 1450... Archaeologists also found two partial deer skeletons and two partial elk skeletons near the bison, Harn said.