Almost nothing is known of the social organization or religious beliefs of the people who erected the menhirs. Their language is also unknown. It is known, however, that they buried their dead and had the skills to grow crops, farm and make pottery, stone tools and jewelry. Identifying the purpose or use of menhirs remains speculative. Until recently, standing stones were associated with the
Beaker people, who inhabited Europe during the European late
Neolithic and early
Bronze Age—later third millennium BC, –1800 BC. However, recent research into the age of megaliths in Brittany strongly suggests a far older origin, perhaps back to six to seven thousand years ago. During the European Middle Ages, standing stones were believed to have been built by the
giants who lived before the
biblical flood. Many of the
megaliths were destroyed or defaced by early Christians; it is estimated that some 50,000 megaliths once stood in Northern Europe, where almost 10,000 now remain. Menhirs have also been found in many other parts of the world. Many menhirs are engraved with
megalithic art, some with
anthropomorphic features. Other common carvings are identified as images of
stone axes, ploughs, shepherds' crooks, and yokes; and are named after these motifs. However, these identifications are not secure except for those of the stone axe images, and the names used to describe them are largely a matter of convenience. Some menhirs were broken up and incorporated into later
passage graves, where they had new megalithic art carved with little regard for the previous pictures. It is not known if this re-use was deliberate or if the passage grave builders just saw menhirs as a convenient source of stone. Where menhirs appear in groups, often in a circular, oval,
henge, or horseshoe formation, they are sometimes called megalithic monuments. These are sites of ancient religious ceremonies, sometimes containing burial chambers. The exact function of menhirs has provoked more debate than practically any other issue in
European prehistory. Over the centuries, they have variously been thought to have been used by
druids for human sacrifice, used as territorial markers, or elements of a complex ideological system, used as
mnemonic systems for
oral cultures, or functioning as early calendars. Until the nineteenth century, antiquarians did not have substantial knowledge of prehistory, and their only reference points were provided by classical literature. The developments of
radiocarbon dating and
dendrochronology have significantly advanced scientific knowledge in this area. ==Geographical distribution==