6,000 years ago Texas was nearing the end of a 1000 year mega-drought. About that time the earth experienced a two hundred year period of diminished solar activity that brought cooler temperatures to Texas. One of the remaining herds of the larger, nearly extinct Bison occidentalis, that required cool temperatures had been hanging on in the prairies west of the Ozark Mountains. When Texas became an inviting habitat these bison began to migrate into Texas and with them came the Calf Creek culture that had specialized in hunting these large animals for centuries. They brought with them a more advanced lithic technology than was common along the Bosque River: The Calf Creek people used one of two dart point types, the Bell ( illustrated; more common in the Erath area) and the even more astonishing Andice; heat-treated to enable the finest craftsmanship, the points were skillfully knapped into large, thin, and deeply basally-notched projectile points that fitted onto a five-foot dart launched from a spear-thrower known as a atlatl. (this was thousands of years before the bow). These hunters had a strong preference for their own flint collected Northwest of Texas, and rather than use the local chert varieties, they re-worked their broken points down to a nub barely recognizable as the Bell. (one clue is the unusually long base) There are clues that each band favored a specific color of flint, a concept still being considered by Texas archeologists. One reason these dart points are considered rare is that the cool spell was brief, only two hundred years, after which the larger-than-present bison type no longer frequented Central Texas and were soon extinct, replaced by the more heat tolerant modern buffalo.