"It may push back, evolutionarily, the appearance of tool use in ape stocks," Mehlman added.
Support for this idea comes from photographs published last month that show gorillas using sticks and branches to navigate areas of swampy forest. That discovery marked the first time tool use had been documented in wild gorillas.
Thomas Breuer, a biologist with the New York-based Wildlife Conservation Society, took the walking-stick images in the Congo rain forest. The pictures show a female gorilla grabbing a branch to gauge the depth of a pool of water before wading across it.
Another female was also seen using part of a bush as a support while digging for food and as a platform to help her cross a patch of muddy ground.
But more complex tool use, such as that shown by Itebero, does not occur in the wild, according to Craig Stanford, an anthropology professor at the University of Southern California in Los Angeles.
Stanford has studied both mountain gorillas and chimpanzees in Bwindi-Impenetrable National Park in southwestern Ugandathe only forest in Africa inhabited by both chimps and gorillas.
The anthropologist says he has never observed any gorilla using tools.
Asked to contrast the intellects and problem-solving skills of chimps and gorillas, he said, "No comparisonchimps win hands-down."
Wild chimpanzees and bonobos can be skilled at selecting tools for particular jobs. For instance, they chose modified sticks for extracting termites from termite mounds, rocks for smashing nuts, and leaves for sopping up drinking water.
But Mehlman says it's wrong to see gorillas as simpletons compared to other great apes.
The primatologist notes that chimpanzees in wild populations take a year or more to learn stone nut-cracking from other group members.
Yet "we have a two-and-a-half-year-old gorilla, albeit in captivity, discovering the process for herself and doing it quite competently."
"Gorillas may be quiet and thoughtful. But [they're] clearly not simpleminded," he added. "Also bear in mind that [lowland] gorillas in wild settings have not been observed nearly as often and frequently as chimpanzees."
Mehlman says future research may uncover many other examples of tool use by wild gorillas.
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