Prehistoric etchings found in a cave in France are the work of children as young as three, according to research.
The so-called finger flutings were discovered at the Cave of a Hundred Mammoths in Rouffignac, alongside cave art dating back some 13,000 years.
Cambridge University researchers recently developed a method identifying the gender and age of the artists.
It is thought the most prolific was a girl aged five. The artists ran their hands down the cave's soft surfaces.
"Flutings made by children appear in every chamber throughout the caves," said archaeologist Jess Cooney, who has pioneered the research in conjunction with Dr Leslie Van Gelder of Walden University in the US.
"We have found marks by children aged between three and seven-years-old - and we have been able to identify four individual children by matching up their marks.
"The most prolific of the children who made flutings was aged around five - and we are almost certain the child in question was a girl."
Each year thousands of people visit the caves in the Dordogne region of western France to admire drawings of mammoths, rhinoceros and horses found within the 8km cave system, which were discovered in the 16th Century.
It was not until 1956 that experts realised that some of the most dramatic were prehistoric.
Archaeologists first determined children had produced some of the finger flutings in 2006. Unlike the sketchings that appear elsewhere in the caves, the markings are made without the application of a colour pigment.
"One cavern is so rich in flutings made by children that it suggests it was a special space for them, but whether for play or ritual is impossible to tell."
Finger fluting also appears in caves in France, Spain, New Guinea and Australia.
"We don't know why people made them," said Ms Cooney, adding that they may have been part of "initiation rituals" or "simply something to do on a rainy day".