By Rebecca Morelle
BBC News science reporter
Bonobos and orangutans are capable of future planning, according to a study published in the journal Science.
Orangutans are our most distant great ape relatives
Researchers found the apes could select a suitable tool for reaching a treat, carry it away, and return with it to retrieve the reward hours later.
Forward planning is thought by some to be a uniquely human trait.
The German team suggests such skills may have evolved about 14 million years ago, when bonobos, orangutans and humans shared a common ancestor.
"We showed that individuals are able to pick up a tool, transport it to a different location, keep it there for at least an hour, and bring it back to solve a problem," explained lead author Dr Josep Call, from the Max Planck Institute for Evolutionary Anthropology.
"Previous studies had shown that chimps and other animals can transport tools to solve a problem on the spot - so they will go and even make a tool and then they will bring it to solve a problem.
"But the main difference with the tasks that we tried is that here when they transport the tool and save it, they have no use for the tool. They need to anticipate that they will require it solve a problem in the future."
The waiting room
The scientists investigated this with a series of experiments.
In one of these, the apes were taught how to use a tool to retrieve a treat from a piece of apparatus.
Then the researchers offered the apes a selection of tools - some suitable, some not - but blocked their immediate access to the reward. Instead, the apes were led away to another location where they had to wait for an hour before being returned to the original room where, if they had selected the correct tool, they could release their treat.
Six out of 16 times the apes successfully chose the correct tool, kept it with them in the waiting room, and then used it to access the reward.
The team found the success rate was about the same when they increased the waiting time to 14 hours - enough time for the apes to sleep in between collecting and using the tool.
The bonobos were able to forward plan
"Traditional learning theory has a hard time explaining this, and several scientists had postulated that future planning is something beyond the capabilities of animals, so we were very surprised to see this," said Dr Call.
The scientists looked at bonobos and orangutans because they represent our closest and most distant great ape relatives, respectively. Humans and bonobos evolved into separate lineages about five to seven million years ago; orangutans about 14 million years ago.
"Because both orangutans and bonobos showed the ability to future plan in these tasks, this means this skill could have been present in the common ancestor to all great apes," Dr Call told the BBC News website.
Next, the team plans to investigate whether the apes will protect their tool if they share the waiting room with a competitor.