Archaeologists found the radius bone of a juvenile Diprotodon (Diprotodon optatum), a 13-foot-long herbivore weighing approximately 3 tons, in Warratyi Rock Shelter's early occupation levels. This is the first time its bones have been found near human artifacts. Image Credit: Peter Murray

 
Archaeologists have discovered a cozy but artifact-rich rock shelter in Australia's arid interior where people ate rhino-sized marsupials and emu eggs around campfires up to 49,000 years ago—about 10,000 years earlier than previously reported. The cave might be the oldest archaeological site in the southern interior, and its treasure trove of data, covering tens of thousands of years of periodic occupation, could help prove that early human settlers spread quite quickly through the continent. The researchers published their findings [PDF] today in the journal Nature.

Giles Hamm, an archaeologist at Melbourne’s La Trobe University, discovered the so-called Warratyi Rock Shelter on a craggy slope in the Flinders Ranges—about 340 miles north of Adelaide—as part of his doctoral research about six years ago. He had been looking at prehistoric rock art along a nearby gorge when he found the cave and noticed its blackened roof—a sign of past campfires. A test pit proved that the soil was full of artifacts and animal bones as deep as 1 meter below the cave’s current floor. “We realized we hit pay dirt,” Hamm tells mental_floss.

A profile view of the Warratyi Rock Shelter, elevated above a local stream. For scale, note the figure at lower right. Image Credit: Giles Hamm

 
The cave was probably only big enough to house a small family, Hamm says, but humans kept coming back to the site for tens of thousands of years, likely because it was near resource-rich springs with water, vegetation, and animals like wallabies and lizards for hunting.

Within the cave’s layers of dirt, Hamm and his colleagues found red ochre and white gypsum powder that might have been used as pigments for body painting. They found a 40,000-year-old needle that could be Australia’s oldest bone tool (see below). They also found innovative stone tools like spears and blades that are 10,000 years older than similar tools found elsewhere in Australia.

This sharpened bone point is 40,000–38,000 years old and is now the oldest bone tool yet found in Australia. It was likely ground from a lower leg bone of an animal about the size of a yellow-footed rock wallaby. Image credit: Giles Hamm

 
The oldest deposits in the cave date back to 49,000 years ago, not too long after the first humans are thought to have arrived in northern Australia. That means people migrated to the southern part of the continent over a relatively short time span. Hamm thinks these prehistoric pioneers might have even traveled by a north-south route through Australia’s harsh interior desert landscape, rather than by a strictly coastal route.

After Homo sapiens evolved in Africa, they ventured out into the rest of the world. But because of gaps in the genetic and archaeological record, there’s lively debate about how and when these early migrations occurred. Today the prevailing theory among scientists is that humans arrived in Southeast Asia around 70,000 years ago, and then island-hopped to Australia at least 50,000 years ago, founding the modern-day Aboriginal population.

“We’ll probably never know the the date for the first people to step on the continent,” Gifford Miller, a geologist at the University of Colorado-Boulder who was not involved in the Nature research, tells mental_floss. “But the new study supports lots of recent work showing that humans were pretty much established throughout the continent earlier than most people thought.”

Archaeologist Mike Smith, who was also not involved in the new research, concluded in his 2013 book The Archaeology of Australia's Deserts that the interior of the continent was probably settled by at least 45,000 years ago. But he tells mental_floss that researchers had been missing significant parts of the archaeological record older than 35,000 years.

There have been some scattered finds that suggested humans spread throughout Australia traveling across some dry desert landscapes quite soon after they arrived on the continent. Radiocarbon dates from Devil’s Lair—a cave near the southwestern tip of Australia that was excavated in the 1970s—showed that humans had occupied the site at least 48,000 years ago. And according to another study published by Miller and his colleagues in Nature Communications earlier this year, there are more than 200 sites across Australia (including some in the interior) with evidence that humans had been cooking eggs of the flightless, human-sized bird Genyornis newtoni, a species that went extinct about 47,000 years ago.

Smith says the Warratyi Rock Shelter helps fill a gap in Australian pre-history with solid evidence.

The animal bones left in the cave also offer new information about how early settlers adapted to and took advantage of their environment. The shelter is the first known site to have human artifacts alongside the bones of the extinct species Diprotodon optatum, a giant marsupial that looked almost like a hippo covered in wombat fur. (See top image.) This could be the first real evidence that humans hunted these lumbering marsupials, and it could help settle the debate about whether human predation pushed the species to extinction.