They are the oldest human fossils ever found on British soil. Excavated 30 years ago at Boxgrove, in West Sussex, the leg bone and teeth of an early human species were subsequently dated as being around 480,000 years old. Other finds made at Boxgrove also revealed these ancient men and women were hunting horses, deer and perhaps even rhinos and butchering them. Crucially, they were doing so with sophisticated stone tools long before the appearance of Homo sapiens - though the exact identity of these individuals remained a puzzle. Initial analysis suggested the bones belonged to a species known as Homo heidelbergensis, a powerfully built people who were originally thought to have evolved in Africa before spreading into Europe. However, another interpretation has suggested the inhabitants of Boxgrove may have belonged to a group of early Neanderthals, a species that originated in Eurasia, and established itself there for the next 400,000 years until dislodged by Homo sapiens. In an attempt to resolve the issue an ambitious British and Spanish project has tried to uncover the identities of these mysterious people by attempting to link them with the former residents of another remarkable fossil site, La Sima de los Huesos – the Pit of Bones – near Burgos in northern Spain. “In essence this is a search for the identity of these early Britons,” said Professor Chris Stringer of the Natural History Museum, London. “The fossils at La Sima have been dated at about 430,000 years old, which is not a great difference in date from the Boxgrove bone and teeth. “Given that chronology, we wanted to know if the people there might be related to the Boxgrove people. A link would give us a crucial clue to the latter’s identity,” Stringer added. La Sima is one the richest human fossil sites in the world. The remains of around 30 individuals have been scraped from the sticky sediments of a vertiginous shaft that drops 50 feet from the deepest recesses of Atapuerca cavern near Burgos. When the bones of La Sima were first discovered, it was thought the pit had been used as a place of burial. More recent research has revealed significant numbers of skull injuries. Some of the individuals whose remains ended up there were apparently deliberately killed and then hurled into the pit. Either way, the pit’s riches – which include complete skulls and backbones – are without precedent and provide a critically important fossil record for the period. “These remains have made it possible to pinpoint the species that then inhabited the area around La Sima,” added Stringer. “From their bones and their DNA, we can say these were early Neanderthals. The question we wanted to answer was straightforward; by comparing remains, could we show that the people of Boxgrove were also early Neanderthals.” So a group of British and Spanish scientists – including Juan Luis Arsuaga, who led the original excavation of La Sima – began a careful comparison of teeth and bones found at both sites. “We hoped to find that together the bones and teeth would tell us these were the same species or demonstrate they were quite separate,” added Matt Pope, of University College London. To their surprise, researchers found neither scenario fitted the evidence. After careful comparisons, the teeth of the people of Boxgrove and the folk of La Sima were found to be very similar, raising hopes that a link between the two populations could be established. But when the legbone– a tibia – from Boxgrove was compared with similar bones from La Sima, they were found to be quite different. “We used CT scans and other measures on the teeth and they were almost identical,” said Stringer. “But the tibia from Boxgrovewas different in shape from ones from La Sima. It is much more robust and, for good measure, it is a different shape. “So we have ended up with a worst-case scenario in a way. Certainly, if we take the evidence at face value, it says the people of Boxgrove and the people of La Sima are different. Possibly the shin bone and teeth at Boxgrove might not represent the people. They were found at different levels in the excavations. The teeth could have been from an early Neanderthal population, while the shin bone was different and more primitive – perhaps representing Homo heidelbergensis after all. Nevertheless, the mystery remains.” However, Pope stressed that much had already been learned in recent years about the people of Boxgrove. “We can see where they made their stone tools to butcher animals. From the flakes they were chipping from stones to make handaxes, you can see how these people were working systematically and co-operatively. They were in command of their raw materials. Boxgrove tells us how they worked. What it does not tell us is where they had their homes or what kind of dwellings they had.” Pope also stressed the importance of the evidence of the similarity in the teeth of the people of La Sima and Boxgrove – despite being separated by 50,000 years and 1000km. “This study brings at least some of the Boxgrove people much closer to early Neanderthal populations of La Sima than we had imagined. We now need to understand why the tibia looks so different. We also need to consider whether we could have more than one population represented in the Boxgrove sequence. Either way, there are exciting discoveries to be made.”