If you picture early humans dining, you likely imagine them sitting down to a barbecue of mammoth, aurochs, and giant elk meat. But in the rainforests of Sri Lanka, where our ancestors ventured about 45,000 years ago, people hunted more modest fare, primarily monkeys and tree squirrels. Then they turned the bones of these animals into projectiles to hunt more of them. The practice continued for tens of thousands of years, making this the longest known record of humans hunting other primates, archaeologists report today.
Many scientists believed such forests lacked the resources for early humans to successfully settle. Instead, our ancestors apparently quickly adapted to this and other challenging environments (such as high elevations and deserts), in part by figuring out how to reliably hunt difficult-to-catch prey.
To conduct the research, archaeologist Patrick Roberts of the Max Planck Institute for the Science of Human History (SHH) in Jena, Germany, and colleagues analyzed animal bones recovered from Sri Lanka’s Fa Hien Cave in Kalutara during excavations from 2009 and 2012. Materials and artifacts including charcoal, faunal remains, shell beads, and bone and stone tools indicate people occupied the site from about 45,000 to 4000 years ago.
The scientists analyzed almost 14,500 animal bones and teeth from four periods of occupation and found that gazelle-size mammals were the most common. Monkeys (primarily macaques and purple-faced langurs, the latter of which inhabit the tallest trees, reaching some 45 meters) and tree squirrels made up more than 70% of the identified remains, which also included otters, fish, reptiles, and birds. Fewer than 4% of the bones came from deer, pigs, and bovids, such as buffalo. Many bones bore cut marks from butchery and had been burned, signs that humans processed them for meat.
The archaeologists also uncovered numerous microliths (minutely shaped stone tools), whose purpose is as yet unknown, but were likely used for hunting. In addition, they identified some three dozen finished or partially completed bone projectile points. These ancient humans were using “bones from the hunted monkeys to hunt more monkeys,” says study co-author Noel Amano, an archaeologist at SHH.
Finally, the remains reveal that the early Sri Lankans were sustainable hunters, primarily targeting adult animals, the scientists report today in Nature Communications. “They hunted these animals for nearly 40,000 years, without driving any to extinction,” Roberts says. “So they must have had sophisticated knowledge of monkey life cycles and an understanding of how to use resources wisely.”
The findings support the idea that, as humans spread across the world, they had to shift from hunting large, roaming animals like mammoth and bison to smaller prey that “could withstand a higher rate of predation,” says archaeologist Robin Dennell at the University of Sheffield in the United Kingdom, who was not involved in the study.
These ancient humans probably already knew how to hunt more agile and elusive game, says Steve Kuhn, an archaeologist at the University of Arizona in Tucson. People had started to hunt small animals in Eurasia about the same time they first entered Sri Lanka, he notes, and so likely arrived with these skills.
Kuhn also cautions that the early Sri Lankans might not have been such wise resource managers; more likely the human populations were small and “didn’t make much of an impact.” They hunted more monkeys and squirrels and fewer deer or pigs, he thinks, simply because the smaller animals were likely more abundant. Like those of us who don’t have time to shop and cook, and so grab a burger, these early people may have simply hunted and dined on the animals that were most readily available.