Atapuerca fossil excavation. Researchers excavating human fossils from the El Portalon site, in Cueva Mayor, in the Sierra de Atapuerca foothills near Burgos, Spain. At bottom centre is the partially exposed skeleton of a 7 year old child. The skeleton, which dates to 5020 to 5030 years ago, shows evidence of the child having rickets and scurvy. It is thought that these diseases were a consequence of the adoption of farming, which decreased the variety of food eaten and so led to nutritional deficiencies. Rickets is caused by a lack of vitamin D. It prevents proper mineralisation of the bones, leading to malformations such as curving. Scurvy is caused by a lack of vitamin C. It is essential for collagen formation, which helps to maintain the integrity of bones.