BURGOS, SPAIN - JULY 16: Researcher Marta Fontanals washes bones and stone tools on the archeological site 'El Mirador' in Atapuerca Mountains on July 16, 2015 near Ibeas de Juarros, in Burgos province, Spain. Atapuerca Mountains' caves contain human remains from early humans that lived in Europe around a million years ago. The caves also contain the remains of animals that no longer live in Europe, as well as extint species. Although the caves were already documented in the 18th century, the archeological excavations only started on 1964. (Photo by Pablo Blazquez Dominguez/Getty Images)
