Scientists at the Antwerp Zoo pitted two species of primate, the bonobo and the chimpanzee, against each other in a puzzle contest. The results surprised the scientists.
The bonobo and the chimpanzee are closely related species. Their habitats are separated by the Congo River. The animals are so similar the two species were not distinguished until the twentieth century. The differences between the two species suggest some explantions for the results of the contest.
Chimps have pale faces at birth, but darken as they age. Males can weigh up to 150 lbs., with some individuals growing much larger. Observers have seen chimpsuse tools in the wild.
Chimps are aggressive and sometimes violent to humans, but have long intrigued us with their similarity to our own species. Michael Jackson kept one for a pet. Ronald Reagan spent more time with them than Republicans want to admit.
Bonobos are born with dark faces. Unlike chimps, they don't go bald with age. Bonobos are smaller and slighter, adult females weighing about 65 lbs. and adult males about 85 lbs. Than have longer legs and smaller heads than chimps. Some say the bodily proportions of the bonobo are a close match for those of Australopithecus, a distant human ancestor.
Many observers say that bonobos are more sexual than chimpanzees. They are more likely to resolve a conflict by having sex than by fighting. Moreover, bonobo social groups look female-dominated to human observers, while chimp groups appear male dominated.
The Antwerp Zoo has a community of chimps in the Antwerpfacility and a community of bonobos in a nearby facility in Mechelen. Scientist devised a series of puzzle boxes for the animals to solve to obtain a walnuts as a reward. To solve the puzzle boxes the animals had to use tools. The chimps were favored to win because they use tools in the wild.
The scientists gave the apes six timed tests, and the bonobos beat the chimps 4-2. The chimps were hampered because the males fought among themselves for dominance. The bonobos--and one female in particular named Djanoa--focused, solved the puzzles, and got the walnuts.
Some might conclude that bonobos are more intelligent than chimps, but this idea doesn't do justice to the questions raised by the contest.
Jeroen Stevens, a zoo scientist who speaks on a Reuters news video about the contest, remarks that motivation might have played a role in the bonobos win. Djanoa may simply have wanted walnuts more than the chimps.
Stevens did not raise a converse notion: social order and a place in the group may be much more important to chimps than walnut treats.
A version of this article appeared on Triond's Scienceray website: http://scienceray.com/biology/are-bonobos-smarter-than-chimps/