Stone tool,Gran Dolina. This stone tool was formed by striking the stone to produce a continuous edge on one or both sides. The most typical piece,characteristic of the Acheulean,is the biface (seen here),which has been struck on both sides and is teardrop-shaped. The fossils and tools found at Gran Dolina date back approximately 800,000 years. Gran Dolina is one of several sites in Sierra de Atapuerca,Spain,that have been studied on and off over the past century,leading to a massive advancement in the understanding of human evolution. In 2000,Sierra de Atapuerca was made a world heritage site by UNESCO |