Rock Shelter (IMAGE) University of Oregon Caption The cave, according to radiocarbon dating, has been shown to be the oldest site of habitation, beginning in about AD 1200. Inside, researchers found remnants of sleeping mats and other evidence indicating 400 years of usage of the cave. Credit Photos courtesy of Douglas Kennett Usage Restrictions Media use only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.