Researchers in the US say they have firm evidence that apes communicate using gestures - shedding light on the development of human language.
The ability to learn gestures separates apes from most species
The team analysed the way bonobos and chimpanzees used hand and limb gestures to make themselves understood.
The scientists found the apes used gestures more flexibly than the way they used facial and vocal expressions.
They say the findings support the theory that human language developed through the use of hand gestures.
Food or sex?
The team comprised researchers from Yerkes Primate Center, at Emory University in Atlanta, Georgia. It found ape groups developed different gestures to say different things and that meanings depended on context.
A male chimpanzee may beg for food from another chimpanzee by gesturing with an extended arm and open hand.
But the same gesture might also be used to ask a female chimpanzee for sex, or between two males as a sign of reconciliation after a fight, said primatologist Frans de Waal, a member of the research team.
"Typically they may use it for food... but they may use the same gesture for something totally different; so, for instance, a male may invite a female for sex by holding out an open hand to her," Dr de Waal said.
This ability to learn gestures distinguishes apes from monkeys and most other species on the planet, the scientist says.
Although all primates use vocal and facial expressions to communicate, only the great apes - chimpanzees, bonobos, orang-utan and gorillas - use gestures as well, an ability they share with humans.
And when apes gesture, they use their right hand, which is controlled by the left side of the brain - the same side as the language control centre in the human brain.
The latest research is published in the Proceedings of the National Academy of Sciences.