Researchers analysing a fossil steppe bison (Bison priscus) cranium found at the Cueva Des-Cubierta, part of the Pinilla del Valle site, in the Lozoya Valley, near Madrid, Spain. This is one of over two thousand mammal remains, mostly the crania of herbivores, found at the site. The remains date from a time when it was inhabited by Neanderthals (Homo neanderthalensis). It is thought that most of the butchering of the head was carried out outside of the cave, with only the processing of the cranium occurring inside the cave. It is not thought that the cave was a natural trap, carnivore den, or a kill or butchering site, and so it is not thought the accumulation of crania was due to subsistence activities, but may have been related to their symbolic use.