When Jane Goodall reported her observations of tools use by chimps to famed anthropologist Louis Leakey, he responded by saying, “Now we must redefine tool, redefine man or accept chimpanzees as humans.” Leakey would have likely had a similar reaction to the current work of University of Calgary archaeologist Julio Mercader, who has uncovered the first tangible evidence that chimps not only use tools but have been doing so and passing along the practice for thousands of years.
In 2004, a close collaboration between the Max Planck Institute for Evolutionary Anthropology (Germany) and the University of Calgary, found stone hammers dating back 4,300 years in the Taï rain forest of Africa’s Côte d’Ivoire. The types of rocks, residual stone flakes and patterns of wear of the stone hammers are similar to those used by modern chimps to crack nuts.
Since the hammers predate human farming in the area, the discovery dispels the notion that the chimp activity was learned by mimicking humans. In fact, Mercader’s research confirms that cultural learning among chimpanzees spanned many generations and that the nut-cracking practice was socially transmitted.
Add to this evidence the similarities between ancient chimpanzee sites and human ones, and Mercader’s work has major implications for theories on human evolution. Mercader’s research shows that chimps, like humans, have “a mental map of the landscape, so they know where things are,” he says. “They knew where the stones were and the nuts and brought them together. They transported the hammers. They didn’t just use any rock where they were. They selected specific kinds of rock in size and hardness that would work as a hammer. Another similarity is the convergence of several individuals to do the activity. It’s a social gathering, which again sounds very human.”
Mercader applied archaeological methods at the ancient chimp sites in the Taï forest and at his tropical archaeology lab at the University of Calgary, which, in itself, was groundbreaking. “The challenge is that archaeology, by definition, is the study of ancient humanity,” he says. “The idea that you could apply it to apes or even some monkeys was absolutely unthinkable.”
While Mercader admits he had a healthy skepticism about excavating a chimpanzee site, he was open to the idea, which is what allowed him to approach the project with a new perspective and make the critical finds. “Trying to see the evolutionary connections — things in common and differences between great apes and our ancestors, and even in ourselves today,” he says, “was quite a methodological challenge.”
Through the discovery of these primate archaeological materials and sites, Mercader and colleagues from six countries have now paved the way for an entirely new discipline: primate archaeology. “There is enough evidence now across the fields — primatology, human evolution and archaeology — to really establish Primate Archaeology,” says Mercader. “It’s not every day that we contribute to a new field of inquiry.”
Under this new discipline, investigators across fields can study great apes and monkeys to determine more about human origins and what makes us distinctly human. “For many years, we thought that what makes humanity is technology and tool use,” says Mercader. “But that is not clear any longer. The way we define humanity has changed. What is the meaning of humanity? It’s not a small question. How are we different from or the same as our ancestors?”
With 2009 celebrating the bicentennial of Charles Darwin's birthday and the 150th anniversary of his seminal book On the Origin of Species, the timing is ripe for a re-examination of evolution and, ultimately, our species.
“The big picture truly is that evolution is not a linear thing. It’s not from A to B. It’s a tree with many different branches,” says Mercader. “Each one of those branches or species is different, however. There can be common tool use or, depending on what we’re looking at, a common ancestor across lines. We help by painting a more complete picture.”