The abrasive qualities of coarse rocks (such as limestone, granite and sandstone) took on great importance at the beginning of the Upper Paleolithic in conjunction with the invention and widespread application of polishing and grinding. These techniques, which to us seem obvious, were revolutionary in enabling Upper Paleolithic peoples to create a whole new range of tools and weapons in bone, antler and (presumably) wood, raw materials that respond poorly to the older technique of percussion. Seen here is a35,000 year old grinding stone from the site of La Combe, France.