The precise start date of acupuncture's use in China and how it evolved from early times are uncertain. One explanation is that some soldiers wounded in battle by arrows were believed to have been cured of chronic afflictions that were otherwise untreated, and there are variations on this idea. Sharpened stones known as Bian shi have been found in China, suggesting the practice may date to the Neolithic or possibly even earlier in the Stone Age.Hieroglyphs and pictographs have been found dating from the Shang Dynasty (1600–1100 BCE) which suggest that acupuncture was practiced along withmoxibustion. It has also been suggested that acupuncture has its origins in bloodletting or demonology.Despite improvements in metallurgy over centuries, it was not until the 2nd century BCE during the Han Dynasty that stone and bone needles were replaced with metal. The earliest examples of metal needles were found in a tomb dated to c. 113 BCE, though their use might not necessarily have been acupuncture. The earliest example of the unseen meridians used for diagnosis and treatment are dated to the second century BCE but these records do not mention needling, while the earliest reference to therapeutic needling occurs in the historical Shiji text (史記, English: Records of the Grand Historian) but does not mention the meridians and may be a reference to lancing rather than acupuncture.The earliest written record of acupuncture is found in the Huangdi Neijing (黄帝内经; translated as The Yellow Emperor's Inner Canon), dated approximately 200 BCE. It does not distinguish between acupuncture and moxibustion and gives the same indication for both treatments. The Mawangdui texts, which also date from the 2nd century BCE (though antedating both the Shiji and Huangdi Neijing), mention the use of pointed stones to open abscesses, and moxibustion, but not acupuncture. However, by the 2nd century BCE, acupuncture replaced moxibustion as the primary treatment of systemic conditions.The practice of acupuncture expanded out of China into the areas now part of Japan, Korea and Taiwan, diverging from the narrower theory and practice of mainland TCM in the process. A large number of contemporary practitioners outside of China follow these non-TCM practices, particularly in Europe.In Europe, examinations of the 5,000-year-old mummified body of Ötzi the Iceman have identified 15 groups of tattoos on his body, some of which are located on what are now seen as contemporary acupuncture points. This has been cited as evidence that practices similar to acupuncture may have been practiced elsewhere in Eurasia during the early Bronze Age.