Scientists excavating a network of caves populated by bats in Spain have been left stunned by the discovery of what they believe to be Europe's oldest pair of shoes. Researchers say the grass-woven sandals are around 6,000 years old - 500 years older than a pair found in another cave in Armenia in 2008.

Miners found the shoes while excavating Cueva de los Murciélagos - which means The Cave of Bats - which has now yielded 76 artefacts since it was first excavated in the 19th century.  The finds include mummified corpses, wild boar teeth and a gold crown.

The quality of the sandals' preservation has been attributed to low levels of humidity and cool winds inside the caves which has prevented the material from decaying. Researchers found that different types of grass were used in their structure, as well as other materials such as leather and lime.

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The study's co-author, Maria Herrero Otal, says the sandals shed new light on the development of mankind. "They are the oldest and best-preserved set of plant fiber materials in southern Europe so far known," she said. "The technological diversity and the treatment of raw materials documented highlights the skill of prehistoric communities.”

The report adds that the Neolithic sandal set represents "the earliest and widest-ranging assemblage of prehistoric footwear, both in the Iberian Peninsula and in Europe." Researchers are also analyzing baskets and a set of tools found inside the cave.

Advances in dating techniques have helped scientists to accurately age the sandals and the other objects found in the caves. The whole collection was found to be around 2,000 years older than originally thought, with the oldest object dating back a staggering 9,000 years.

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