<p><strong>Perched in some cases on precarious cliff ledges, centuries-old log coffins</strong>—<strong>such as this one, pictured alongside researcher<a href="http://anatomy.otago.ac.nz/index.php?option=com_content&amp;task=view&amp;id=622&amp;Itemid=46"> Nancy Beavan</a></strong>—<strong>and "body jars" are the only known traces of an unknown <a href="http://travel.nationalgeographic.com/travel/countries/cambodia-guide/">Cambodian</a> tribe. Now new dating studies are beginning to assure the unnamed culture a place in history.</strong></p><p>Ten such burial spots have been found in the <a href="http://maps.nationalgeographic.com/map-machine#s=h&amp;c=12.098409789924842,%20103.49807739257814&amp;z=9">Cardamom Mountains (map)</a> since 2003, and at least one is at least 160 feet high (50 meters)—the intention apparently being that "anyone trying to disturb the burials would break their neck," said Beavan, who led the new study.</p><p>Beavan's team has radiocarbon-dated wood, teeth, and bones from four of the sites to between A.D. 1395 and 1650, placing them smack-dab in the decline of the Khmer Empire, based in <a href="http://travel.nationalgeographic.com/travel/world-heritage/angkor/">Angkor</a>. However it's unclear what, if any, influence the empire had on these mountain people, said Beavan, of the University of Otago's Department of Anatomy in New Zealand.</p><p>Until now, experts had no idea when the sites had been established or how long they'd been in use, she added.</p><p>(<a href="http://news.nationalgeographic.com/news/2007/08/photogalleries/Angkor-pictures/">Pictures: Angkor's Ancient Enormity Uncovered.</a>)</p><p><em>—James Owen</em></p>