Ancient humans, fearless squirrel hunters

Ancient humans hunted and killed fleet-footed tree-dwelling mammals – including monkeys and giant squirrels – far earlier than previously thought.

Detailed excavations of a rainforest cave in Sri Lanka show that anatomically modern humans as far back as 45,000 years ago used sophisticated hunting strategies to capture the wily animals.

The findings, published in the journal Nature Communications, could help to explain how Homo sapiens were able to colonise a range of extreme environments and why they are today the solitary survivors from a family tree that once included Neanderthals, Denisovans and other archaic human species.

“Rainforests are notoriously difficult to be able to live in successfully,” says archaeologist Michelle Langley from Griffith University in Australia, who led the study’s tool analysis. 

“They don’t have as many resources as savannahs, which have large herds of big animals like antelope or bison. The animals they do have tend to be hard to find, or they’re up in the trees where you need pretty special technologies to get them.”

Added to this, says Langley, are jungle predators, such as tigers and jaguars, and diseases that go hand-in-hand with the damp environment.

Despite this, ancient human remains have been found dotted throughout rainforest areas in southeast Asia and New Guinea. How ancient communities eked out a living in these unforgiving environments hasn’t always been clear.

The Fa-Hien Lena cave in southwestern Sri Lanka is the earliest site of human occupation on the island. Human remains found there – comprising three children and an adult female – date to around 30,000 years ago. 

The latest study, led by researchers at the Max Planck Institute for the Science of Human History in Jena, Germany, is the first to systematically sift through the thousands of animal bones and small stone and bone tools dug from layers of soil in the cave.

All said, more than 14,000 bone and tooth fragments were scrutinised.

The painstaking work reveals that the cave’s occupants ate monkeys and large squirrels, and consistently targeted large adult specimens, “so they’re getting their bang for their buck”, says Langley.

Small pointed bone tools, fashioned from the limb bones of the animals they caught, were also found, suggesting the people had developed a refined and sophisticated technology to exploit their surrounds.

Isotope dating of the remains indicate people were hunting small mammals as far back as 45,000 years ago, 20,000 years earlier than evidence of such practices from Europe and West Asia.

“This ‘monkey menu’ was not a one-off, and the use of these difficult-to-catch resources is one more example of the behavioural and technological flexibility of Homo sapiens,” says anthropologist Michael Petraglia of the Max Planck Institute for the Science of Human History, a senior author of the study.

“With these kind of studies, we’re now starting to appreciate how easily we were able to adapt our technologies to really different environments and really extreme environments,” says Langley.

She and her colleagues are now looking closer at the bone tools to figure out how they were used: “Were they using blow darts, was it a bow and arrow, was it a spear, were they hand-throwing things, or was it a trap with something attached to it?”

Whichever it was, the technology was complex and deliberate. “It’s not like they just chucked something together that might work,” she says.