Goma, Congo ? A young gorilla in a Congo sanctuary is smashing palm nuts between two rocks to extract oil, surprising scientists who say they have much to learn about what gorillas can do – and about what it says about evolution.

It had been thought that the premeditated use of stones and sticks to accomplish a task like cracking nuts was restricted to humans and the smaller, more agile chimpanzees.

Then in late September, keepers at a Dian Fossey Gorilla Fund International sanctuary in eastern Congo saw 2 1/2-year-old female gorilla Itebero smashing palm nuts between rocks using the “hammer and anvil” technique, considered among the most complex tool-use behaviors.

Dian Fossey Gorilla Fund primatologist Patrick Mehlman said the finding indicates that complex tool use may not be a trait developed only by humans and chimpanzees and could have its origins earlier in the evolutionary chain – among ancestors common to both humans and their closest relatives, the great apes.

Itebero has been living in the sanctuary for a year. Mehlman said he believed Itebero started cracking nuts spontaneously and was not influenced by humans.