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Wednesday, October 3, 2007

sex makes bonobos better cooperators

Our big finding last year was that bonobos are better cooperators than chimps.

Which was surprising because for many years field researchers have seen chimpanzees cooperate to hunt meat. We knew from previous experiments that chimpanzees could do the cooperation task. In fact, the Ngamba Island chimps were the world champions. What we wanted to know was, could bonobos, who had never done the test before but are famous for their tolerance, cooperate as well as or better than chimpanzees?

The experiment consists of a long red plank with a rope threaded through two metal eyes. Food can either be placed at either end or in the middle of the plank. If both apes pull on the rope together, they can pull the plank towards them and get the food. If only one ape pulls on the rope, it comes unthreaded and the plank doesn’t move.

What we found was that as long as the food was in two separate piles on either end of the plank, the chimps could cooperate fine. But as soon as you put the food in one monopolizable pile in the middle, chimpanzee cooperation falls apart. Even though we know the chimps doing the test were relatively tolerant of each other and had done similar tests many times before, when the food could be monopolised by one chimp, most of the time the other one refused to pull.

However with the bonobos, even though they had never seen the test before, when the food was in one pile they played and had sex to negotiate with each other so that they pulled the ropes together with no problems.

So what we have are chimps who cooperate a lot but aren’t very tolerant, and bonobos who are very tolerant but don’t really cooperate. What probably happened with humans when we split from our common ancestor with chimpanzees and bonobos six million years ago is that we became very tolerant which allowed us to cooperate in ways that had never before been seen before.

So now we’re doing more cooperation experiments. I like testing Kiwit because he always pulls the rope.