Italian scientists have discovered three fossilized trails of footprints that early humans left about 350,000 years ago as they descended the treacherous flanks of an active volcano.
The scientists believe the footprints are the oldest such prints ever uncovered of Paleolithic humans, who preceded modern humans.
One of the footprint trails found in the rugged volcanic terrain in southern Italy zigzags to follow a steep incline's safest path down. Another includes handprints the individual left as he steadied himself in a precarious spot, only to slide a short ways down the slope.
"You're looking at an event that happened 350,000 years ago — someone made an imprint on a surface, walking in a way you'd expect to see someone in these same conditions walk today," said Owen Lovejoy, an anthropologist at Kent State University who was not involved in the research.
"It adds another cog in the connect between ourselves and our ancestors."
Who left the 56 footprints isn't clear. But their discoverers suggest either late Homo erectus or Homo heidelbergensis — two early human species found during the Paleolithic era.
The findings appear in Thursday's issue of the journal Nature.
The footprints' makers were short — just under 5 feet tall — based on the prints' petite size of less than 8 inches in length, the researchers said.
Like footprints in wet sand, the trails were left by three individuals who walked across a cooled but recent pyroclastic flow, a dense mixture of rock fragments, ash and gases.
A short time later, the volcano erupted again, blanketing the footprints with a thick layer of ash that preserved them for the ages, said Paolo Mietto of the University of Padua, Italy.
"The idea that these humans were escaping an eruption . . . is attractive, and is supported by the fact that all tracks have the same direction, outwards from the volcano's main crater," said Mietto, who concedes that such a scenario is only a theory.
The footprints have been dated at between 325,000 and 385,000 years. At that time, Mietto said southern Italy was covered with forests, mountains and the same volcanic ranges still found there. For humans, life in that era was almost certainly brutal and relatively brief.
Local residents had long known of the footprints, and referred collectively to them and fossilized animal tracks also preserved near the volcano as "devils' trails."
Two amateur archaeologists told Mietto about the tracks spread over about a mile-square area, and he and a colleague visited the site. They soon realized that early humans left them.
Mietto said the prints are unmistakably human in origin, as some preserve the foot's plantar arch and individual toeprints.
The fact that the early humans who left the tracks walked upright on two feet is no surprise because that ability dates back millions of years, said Tim White, a University of California paleontologist who co-discovered the famous "Lucy" hominid fossil in Ethiopia in 1974.
That nearly complete fossil belongs to a species now known as Australopithecus afarensis, a primate the size of chimpanzee that walked upright.
Footprints left by the same creatures were found in 1977 in Tanzania, imprinted in volcanic mud 3.6 million years old — making them 10 times older than the new discovery. Because the new tracks are comparatively recent, White said they shed no light on human origins.
"The bottom line is that these are interesting curiosities that do not advance our knowledge of what happened when in human evolution," he said.