Researchers carrying out excavations at the Sima del Elefante, Spain. A hominid jawbone fossil dating 1.4 million years old was found at the archaeological site. 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.