Indiana Jones may be flying over the Nazca Lines in Peru in his latest Hollywood adventure, but two British archaeologists have been investigating the enigmatic desert drawings for several years.

Dr Nick Saunders from Bristol University and Professor Clive Ruggles from the University of Leicester are locating and measuring the lines with high-precision GPS, photographing the distribution of 1,500-year old pottery, and painstakingly working out the chronological sequence of overlying lines and designs.

Funded by the Anglo-Peruvian Cultural Association in Lima, their research hopes to unlock the purpose of the dazzling but confusing array of desert drawings.

Bizarre explanations, such as alien visitations, ancient landing strips, and astronomical calendars are being replaced by serious archaeological and anthropological ideas.

Professor Ruggles and Dr Saunders agree with other experts that some lines were pathways across the desert, others had a more religious significance, while some appear associated with desert scars caused by flash-floods, and are probably linked to the veneration of water.

“Identifying which lines came first, whether they were spiritual or functional, and exactly how they were used during a thousand years of prehistory is a great challenge,” said Dr Saunders.  “The treasure is not gold but insight, and the mystery is cultural not extraterrestrial.”