Deer stones (also known as reindeer stones) and the omnipresent kheregsüürs (small kurgans) probably are from this era; other theories date the deer stones as 7th or 8th centuries BC. Deer stones are ancient megaliths carved with symbols that can be found all over central and eastern Eurasia but are concentrated largely in Siberia and Mongolia. Most deer stones occur in association with ancient graves; it is believed that stones are the guardians of the dead. There are around 700 deer stones known in Mongolia of a total of 900 deer stones that have been found in Central Asia and South Siberia. Their true purpose and creators are still unknown. Some researchers claim that deer stones are rooted in shamanism and are thought to have been set up during the Bronze Age around 1000 BC, and may mark the graves of important people. Later inhabitants of the area likely reused them to mark their own burial mounds, and perhaps for other purposes. In Mongolia, the Lake Baikal area, and the Sayan and Altai Mountains, there are 550, 20, 20, and 60 known deer stones respectively. Moreover, there are another 20 deer stones in Kazakhstan and the Middle East (Samashyev 1992) and 10 further west, specifically in Ukraine and parts of the Russian Federation, including the provinces of Orenburg and the Caucasus, and near the Elbe River (Mongolian History 2003). According to H.L. hlyenova, the artistic deer image originated from the Sak tribe and its branches (Chlyenova 1962). Volkov believes that some of the methods of crafting deer stone art are closely related to Scythians (Volkov 1967), whereas Mongolian archaeologist D. Tseveendorj regards deer stone art as having originated in Mongolia during the Bronze Age and spread thereafter to Tuva and the Baikal area (Tseveendorj 1979).