Paleontologist and co-ordinator of Sima del Elefante archaeological site Rosa Huguet (centre) and paleoanthropologist and codirector of the Atapuerca Team Juan Luis Arsuaga (right) at Sima del Elefante archaeological site where a hominid jawbone fossil was found. The jawbone is thought to be the oldest discovered remains of a human ancestor in Europe. Sima del Elefante site is located in the Trinchera del Ferrocarril, a trench that was dug in the foothills of Sierra de Atapuerca at the end of the 19th century. As well as a rich collection of mammal fossils dating back to between 1.25 and 1.5 million years, stone tools have been found at this site. The extensive discoveries at the Atapuerca sites have led to numerous advancements in the understanding of human evolution.