Chimpanzees perched in the lush forests of West Africa, cracking nuts with carefully selected stones, might not just be feeding themselves—they may also be revealing secrets about our ancient ancestors.

A recent study has uncovered striking parallels between how chimpanzees choose tools today and how early humans selected theirs 2.5 million years ago.

A Hammer and an Anvil: Tools of the Trade

Researchers from an international team of paleobiologists, anthropologists, and behavioral scientists observed chimpanzees as they tackled one of the most enduring challenges of the animal kingdom: cracking open tough nuts. But this was no mere snack break—it was a window into the evolutionary roots of tool use.

Nutcracking for chimpanzees is a two-tool affair. The “hammer,” held firmly in the hand, delivers powerful strikes to the nut resting on the “anvil,” a sturdier surface that absorbs the blows. Success depends on the chimps’ ability to select the right stones for each task.

The team, led by Dr. D.R. Braun and Dr. Susana Carvalho, introduced unfamiliar stones like dacite and carbonatite to the chimpanzees at Bossou, Guinea. These stones, transported from East Africa, had mechanical properties similar to those used by hominins at sites like Kanjera South, Kenya.

Stones were randomized in a controlled outdoor laboratory. The chimpanzees’ choices were observed over weeks, revealing striking patterns. Hard, durable stones like dacite were consistently chosen as hammers, while softer stones like carbonatite were preferred as anvils.

Remarkably, the chimpanzees weren’t guided by color or texture—properties easily distinguishable by humans. Instead, they relied on trial and error to discern each stone’s mechanical properties. Eventually, they learned that harder, heftier stones are good for hammers, while softer, more stable stones are ideal as anvils.

Lessons From a Shared Legacy

“These patterns of stone selection parallel what is documented for Oldowan hominins,” the researchers noted.

Oldowan tools, among the earliest known, date back roughly 2.5 million years. These rudimentary stone tools were used for chopping, scraping, and cutting by ancient human ancestors, including Australopithecus garhi and Homo habilis. Much like the chimpanzees, Oldowan hominins deliberately selected stones with specific properties, refining their tool choices over generations.

Hominins of the Oldowan period transported select stones over vast distances, sometimes exceeding 10 kilometers, to craft tools for butchering animals and processing plants. These choices reflect an advanced understanding of rock mechanics.

Yet the Bossou chimpanzees show that such intelligence isn’t uniquely human. Their stone tool selection, driven by a mix of individual learning and cultural transmission, suggests a shared evolutionary foundation. Adults in the community demonstrated mastery over tool selection, while juveniles often learned by imitating their elders. Sounds familiar?

Previously, researchers at the University of Zurich reached similar conclusions in 2022, showing that chimpanzees don’t automatically know how to crack nuts with stone tools; they learn this behavior by watching others and learning from them.

The researchers also noted a peculiar efficiency. Over time, the chimpanzees improved their combinations of hammers and anvils, reducing the number of strikes needed to crack a nut. This ability to refine techniques likewise mirrors the adaptive strategies of early humans refining tool use to optimize effort.

The Oldowan tradition eventually gave rise to Acheulean tools—sleek hand axes and other refined implements crafted by Homo erectus. But the fundamental principles of tool selection remained the same.

What Does This Mean for Human Evolution?

The parallels between chimpanzee and hominin behavior challenge long-held assumptions. For decades, tool use was considered a uniquely human trait, tied to the emergence of the genus Homo. But studies like this push the timeline further back, suggesting that complex tool use might have deeper roots in the primate family tree. Chimpanzees (and bonobos) are humanity’s closest living relatives, sharing approximately 98% of our DNA.

The findings also enrich the emerging field of primate archaeology, which bridges behavioral studies of living primates with the archaeological record. By studying chimpanzees, researchers might infer the social and ecological dynamics that shaped ancient tool use.

The next time you hold a tool in your hand, consider this: you’re carrying on a tradition that began millions of years ago, with a stone and a nut.

The study appeared in the Journal of Human Evolution.