By Victoria Gill
Science reporter, BBC News
The microscopic samples were found in the Dzudzuana Cave in Georgia
A Georgian cave has yielded what scientists say are the earliest examples of humans making cords.
The microscopic fibres, discovered accidentally while scientists were searching for pollen samples, are around 30,000 years old.
A team reports in the journal Science that ancient humans probably used the plant fibres to carry tools, weave baskets or make garments.
Some of the fibres are coloured and appear to have been dyed.
The fibres were discovered preserved within layers of mud in Dzudzuana Cave in Georgia.
"It's impossible to know exactly how they were used, but some of them are twisted," said Ofer Bar-Yosef, a researcher from Harvard University in the US who took part in the study.
"This is a very old principle of making rope and cord."
Only microscopic pieces of the fibres were still evident in the cave.
Some of the fibre samples were twisted and some were coloured
Dr Bar-Yosef explained they were preserved within the mud that accumulated and held in the deep layers of the cave for thousands of years.
"Just a few cords or strings probably rotted away," he told BBC News.
Dr Bar-Yosef's colleague, Eliso Kvavadze, was actually searching for pollen, which the researchers examine in order to reconstruct the environment of the site through the ages.
Dr Bar-Yosef said: "This was an absolutely accidental surprise.
"I didn't believe it at first... so we checked each of the sections of the cave and we found that it's basically everywhere within that layer."
Some of the fibres are coloured, and the scientists believe they were dyed using natural plant-derived pigments that would have been "available to the Upper Paleolithic occupants of the cave".