Researchers including Spanish anthropologist Prof. Juan Luis Arsuaga (standing, centre) examining marks on Skull Number 5 using a microscope as part of taphonomy studies carried out on the 7,800 fossils from the Sima de los Huesos site. This is to clarify the origin of the accumulation of 29 corpses at the site. Skull Number 5 was excavated in 1992 from the Sima de los Huesos pit in the Atapuerca foothills in Spain, and dates from around 400,000 years ago. This research is being carried out in the Museum of Human Evolution in Burgos, Spain since Skull Number 5 in the photo is currently on display in the museum.