Nicholas Mulcahy and Josep Call of the Max Planck Institute for Evolutionary Anthropology in Leipzig tested whether our closest great ape relative--the bonobo--and our most distant--the orangutan--share our ability to plan for the future. The researchers first trained five bonobos and five orangutans to use a tool to get a fruit treat from a mechanical apparatus. They then blocked access to the treat but allowed the apes to handle suitable and unsuitable tools for the task before ushering them into a waiting room for an hour. After that hour, they were brought back into the first room and, if they had brought the right tool, they could use it to get the treat.
The apes both took a suitable tool out of the test room and brought it back in with them after the waiting period significantly more often than predicted by chance. A female orangutan named Dokana proved particularly adept, completing the task successfully in 15 out of 16 attempts. Even when the delay time was extended through the night--14 hours--Dokana succeeded in garnering the tool and the fruit more than half of the time. A bonobo named Kuno did even better with the long delay than the short one, completing the task in eight out of 12 attempts.
To determine whether the apes were simply associating the tool with the food reward, or whether they were actively planning ahead, the researchers devised two more tests. In the first, two of the bonobos and two of the orangutans faced a similar challenge but with only juice as a reward--to discount for the possibility that the apes had taken the right tool previously simply because they were currently hungry. Again, the apes proved capable.
Finally, some nave apes were presented with tools but not the mechanical apparatus. If they brought back the right tool they were still rewarded with a treat. But most did not, seemingly disproving a simple associative link between the tool and the treat. "Apes selected, transported and saved a suitable tool not because they currently needed it but because they would need it in the future," the authors write in the paper presenting the research in today's Science.
That bonobos and orangutans can plan ahead suggests that the ability evolved in the great apes prior to 14 million years ago rather than in our hominid forebearers within the past 2.5 million years, the scientists note. And other creatures may have undergone convergent cognitive evolution. Indeed, another study published online yesterday by Science found that scrub jays hid and re-hid food depending on whether they were watched by other birds.