Furthermore, de Waal believes that there is already evidence for cumulative culture in chimpanzees, such as populations that create and use tools for cracking nuts and extracting termites. "It is hard to imagine that chimpanzees socially learn these more complex behaviors without first learning more basic forms," de Waal says.
Laland, for his part, is concerned that the evidence for culture in nonhuman species is still circumstantial. The innovations are basic enough that it does not rule out the possibility these tools developed separately rather than building on one another. One species, Laland concedes, has unusually persuasive evidence: the New Caledonian crow, an animal far away from humans in evolutionary terms. The species, which like the western scrub jay is a member of the Corvidae family, makes tools by shaping pandanus tree leaves to forage for insects in wood. A survey of these tools has revealed three distinct designs, and the geographic overlap in their use suggests they did not evolve independently but may have been created by modifying one form of tool into another—evidence for cumulative culture.
The crow example may seem primitive when compared with the technical achievements of humans. Yet it raises questions about the capabilities involved, how they evolved and how many animals might possess these capacities. If nothing else, it reminds us that we are looking at a spectrum of abilities—and the differences, as Darwin suggested, are more likely to be of degree than kind.