Whether it's a special technique for basket-weaving or using a stick to "fish" for tasty termites, the ability to share and modify cultural behavior probably originated with the last common ancestor to humans and chimpanzees, a new study argues.
In a paper published Monday in the journal PNAS, researchers concluded that humans and their closest animal relatives, chimpanzees, shared diverse cultural repertoires, while the more distantly related orangutans did not.
Study authors Jason Kamilar, a primatologist at Arizona State University, and Quentin Atkinson, a cognitive and evolutionary anthropologist at the University of Auckland in New Zealand, examined the so-called nesting of cultural traits in humans and compared them with the putative cultural behaviors of chimps and orangutans.
"In both humans and chimpanzees, cultural diversity is highly non-random, showing significant nested structure," the authors wrote. "We find no evidence of nestedness in the orangutan."
Previous research comparing cultural diversity of humans and chimps has been controversial. According to scientists, the human primate lineage diverged from chimpanzees roughly 6 million years ago, while humans and orangutans diverged roughly 13 million years ago.
Primatologists have noted the diversity of behaviors that chimpanzees learn and pass on. For example, while one group of chimpanzees might use a twig to dig for honey from a tree, another group might use chewed leaves to soak the honey up like a sponge.
Such variations in technique are likely to be found in chimp groups that are geographically distant, while groups that are closer tend to share similar behaviors, researchers say.
In preparing their study, the authors examined human tribes in New Guinea and Native Americans in California, and considered such cultural practices as wearing nose ornaments and fashioning earthenware and bows and arrows, as well as traditions of basket-making and basket use.
When it came to chimpanzees and orangutans, the researchers examined such practices as using sticks to capture ants and termites for food, using stones or wood to smash nuts, and communicating by rapping knuckles, among other behaviors.
The study authors said that unlike the case with humans and chimps, orangutan cultural diversity appeared to be more of a function of random chance than geography.
They acknowledge, however, that this could be the result of overall loss of habitat among orangutans, as well as a their "less gregarious social organization" in comparison to humans and chimpanzees.