The complete genetic code of a stone age woman has been recovered from a piece of ancient chewing gum, the first time such a feat has been achieved without any human body parts.

Archaeologists have known for some time that people as far back as the Neanderthals used tar from birch trees to make sticky adhesive for mounting tools. And tooth marks found in discarded pieces suggested they had also chewed the tacky substance, possibly to soften it to make it more malleable for working.

Researchers at the University of Copenhagen found a 5,700 year old piece of ancient gum during excavations at Syltholm, east of Rodbyhavn in southern Denmark, ahead of the building of a new tunnel.

When they analysed the pitch they found the complete genome of a late Mesolithic or early Neolithic female. The DNA showed she had dark hair, dark skin and blue eyes. And her last meal before she spat out the gum had been duck and hazelnuts.

It is the first time that a full genetic sequence from an ancient site has been recovered without the need for bones and represents a new untapped resource for archaeologists looking for clues about past populations.