Chimpanzee smashing rocks.
Unlike early human species, chimpanzees do not seem to be able to spontaneously make and use sharp stone tools, even when they have all the materials and incentive to do so, according to a behavioral study published in the journal Open Research Europe.
An international research team wanted to find out whether chimpanzees—one of the closest living relatives of humans—also possess the spontaneous ability to make sharp-edged stone tools. "This had previously been tested exclusively on great apes that had been enculturated or trained by humans and had been shown manufacturing techniques by humans," says study author Dr. Alba Motes-Rodrigo.
In the new experiments eleven chimpanzees at a zoo in Kristiansand, Norway, and Chimfunshi Wildlife Orphanage, a sanctuary in Zambia, were given two different sealed containers that contained food—visible through a Plexiglas pane. But they could only get at it by making stone tools.
They were given a stone core and hammer stones to knock sharp-edged stones off this core. Unlike in all previous studies, the apes tested were not given the opportunity to learn how to make such tools by observing experienced individuals or humans.
Although the chimpanzees likely understood that the containers contained food and although they were also clearly motivated to get their hands on the food rewards, none of the animals in the test even attempted to make and use stone tools.
The research team concludes that chimpanzees do not have the spontaneous ability to create complex tools from rocks, even if they use stones in the wild.
In 1987, chimpanzees in southeastern Guinea, eastern Liberia and western Ivory Coast were observed to use large rocks to crack open 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 rocks to use as a sort of hammer and as an anvil.
In 2007, archaeologists announced the discovery of 4,300-year-old "stone factory for nut-cracking" 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 remains of nuts that modern chimpanzees like to snack on. But the ancient "hammer and anvil stones" are identical to modern ones, showing no progress in the tool-making abilities of chimpanzees.
The lineages of humans and great apes separated about seven million years ago. The ability to make and use sharp stone tools probably developed in humans long after this separation.
The first stone tools made by early hominids appeared in Africa about 2.6 million years ago. They were made from chipped cobbles or larger flakes that had been carefully selected for size and weight. Such simple tools persisted almost unchanged until about 250,000 years ago, when more elaborate tools, like blades or small, delicate artifacts, appear in the archaeological record.
Complex stone tool made and used by humans.
