Humans developed tool use some 2.5 million years ago in Africa. The first tools were made from chipped cobbles or larger flakes that had been carefully selected for size and weight. Simple stone tools persisted almost unchanged until about 250,000 years ago, only then more elaborate tools, like blades or small, delicate artifacts, appear in the archaeological record.
For a long time, it was believed that the manufacture and use of tools was a typical human trait. However, observations made in the last decades show that also animals can use tools. In 1987 chimpanzees in southeastern Guinea, eastern Liberia and western Ivory Coast were observed to use large rocks to crack open hard palm nuts. Older chimpanzees teach younger ones the needed skills, showing them where to find outcrops of bedrock in the jungle and how to select the best stones to use as a hammer and as an anvil. In 2007 archaeologists announced the discovery of 4,300-year-old stones with traces of use in the midst of the rainforest of the Ivory Coast. The stones were much bigger than anything a human could use comfortably and bore the residue of nuts that modern chimpanzees like to snack on. Although chimpanzees are the best-known tool users among animals, they are by no means the only ones. Studies in Brazil and Panama have shown how capuchin monkeys use stones, sometimes as large as they are, to crack open palm nuts in much the same way that chimpanzees do. A team from the University of Oxford showed that capuchins use of stones as nut-cracking tools dates at least into the 13th century, more than 200 years before Columbus arrived in the Americas. Long-tailed macaques living on islands off Thailand use stone hammers so successful that they are pushing the local rock oyster population into extinction.
The use of tools by primates may not be that surprising, as humans are also primates, however, also animals like sea otters, birds and even fish can use stone tools. Some birds, like the bearded vulture, drop bones on stones to crack open the hard bones and to get to the soft marrow. New Caledonian crows sometimes use stone anvils. Even Tusk Fish were filmed smacking cockle shells against reef boulders to crack them open. Unfortunately it is very hard that such behaviour will enter the archaeological record, as the used “tools” show no distinct wear pattern.
Sea otters are known to fish for small pebbles, place them on their chest and then crack open shellfish on them. Where no small stones can be found, they also bash mussels against large rocks on the seashore. It is not clear how old this behavior is, but new research may hold the answer to this question. Analyzing a site at Bennett Slough Culverts in California where sea otters use rocks as tools for cracking open mussels, a team from the Max Planck Institute for the Science of Human History in Germany has shown that this leaves distinctive wear patterns on the large rocks. Using the same techniques used for the study of ancient human sites, archaeologists could identify ancient sites where sea otters used large stones in this way.