Excavations in a cave in the mountains of northern Spain have uncovered the oldest known remains of human ancestors in Western Europe, scientists reported Wednesday.

The fossils of a lower jaw and teeth, more than 1.1 million years old, were found in sediments along with stone tools and bones of animals that appeared to have been butchered. The remains have been attributed to the previously known species Homo antecessor, a possible ancestor of Neanderthals and modern humans.

The discovery is described in the current issue of the journal Nature by Spanish and American scientists led by Eudald Carbonell of the Catalan Institute of Human Paleontology and Social Evolution at Tarragona, Spain. The scientists, noting that the earliest presence of human ancestors in Europe is “one of the most debated topics in paleoanthropology,” said the site, Sima del Elefante in the Atapuerca Mountains, held the “oldest, most accurately dated record” of both fossils and artifacts of human occupation in Western Europe.

Other sites on the Continent yielded artifacts of a roughly comparable age, but no fossil bones. Until now, the earliest remains of Homo antecessor, from the same mountains, were 800,000 years old.