Scores of human fossil footprints dating back to the ice age 20,000 years ago have been discovered in southeastern Australia.
The 124 well-preserved prints are between 19,000 and 23,000 years old, based on optical dating techniques, the researchers said.
The prints range in size from 13 centimetres to 30 centimetres and provide clues about the anatomy and behaviour of the men, women and children who left their mark in the moist soil.
"We see children running between the tracks of their parents, the children running in meandering circles as their parents travel in direct lines," New South Wales Environment Minister Bob Debus told the Australian Broadcasting Corp.
It's a "most extraordinary snapshot of a moment or several moments in the life of aboriginal people living on the edge of a lake in western New South Wales 20,000 years ago."
University of Melbourne archaeologist Matthew Cupper and his colleagues describe the prints in Mungo National Park near Willandra Lakes, southwest of Sydney.
"The trackways form the largest collection of Pleistocene human footprints in the world," the researchers write in this week's online issue of the Journal of Human Evolution.
"This site offers a unique glimpse of humans living in the arid inland of Australia at the height of the last glacial period."
Based on the size of the prints and the pace lengths, the researchers say the tracks point to tall individuals. One six-foot tall man appeared to be sprinting at about 20 kilometres per hour.
The Pleistocene period occurred around 1.8 million to 10,000 years ago and include the most recent ice age.
A woman named Mary Pappin Junior from the Mutthi Mutthi aboriginal group found the first footprints in August 2003, Cupper said.
The tracks were left in silty clay that hardened and were then preserved by a layer of clay and sand from dunes.
With files from Australian Broadcasting Corporation