A 3rd Millennium Origin of Early Alphabetic?

Christopher Rollston gives a fascinating discussion of recent finds of clay cylinders at Tell Umm el-Marra in Western Syria that appear to be inscribed in Early Alphabetic script. They were found in what is said to be a firm 3rd millennium BCE archeological context, which Rollston concedes could imply that Early Alphabetic was invented earlier than is normally assumed (19th-18th centuries BCE).