This flaking produced sharp edges which could be used as tools, primarily in the form of choppers or scrapers. These tools greatly aided the early humans in their hunter-gatherer lifestyle to perform a variety of tasks including butchering carcasses (and breaking bones to get at the marrow); chopping wood; cracking open nuts; skinning an animal for its hide, and even forming other tools out of softer materials such as bone and wood. The earliest stone tools were irrelevant, being little more than a fractured rock. In the Acheulian era, beginning approximately 1.65 million years ago, methods of working these stones into specific shapes, such as hand axes emerged. This early Stone Age is described as the Lower Paleolithic. The Middle Paleolithic, approximately 300,000 years ago, saw the introduction of the prepared-core technique, where multiple blades could be rapidly formed from a single core stone. The Upper Paleolithic, beginning approximately 40,000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely. The end of the last Ice Age about 10,000 years ago is taken as the end point of the Upper Paleolithic and the beginning of the Epipaleolithic / Mesolithic. The Mesolithic technology included the use of microliths as composite stone tools, along with wood, bone, and antler tools. The later Stone Age, during which the rudiments of agricultural technology were developed, is called the Neolithic period. During this period, polished stone tools were made from a variety of hard rocks such as flint, jade, jadeite, and greenstone, largely by working exposures as quarries, but later the valuable rocks were pursued by tunneling underground, the first steps in mining technology. The polished axes were used for forest clearance and the establishment of crop farming and were so effective as to remain in use when bronze and iron appeared. These stone axes were used alongside a continued use of stone tools such as a range of projectiles, knives, and scrapers, as well as tools, made organic materials such as wood, bone, and antler. Stone Age cultures developed music and engaged in organized warfare. Stone Age humans developed ocean-worthy outrigger canoe technology, leading to migration across the Malay archipelago, across the Indian Ocean to Madagascar and also across the Pacific Ocean, which required knowledge of the ocean currents, weather patterns, sailing, and celestial navigation. Although Paleolithic cultures left no