Bonobos and the Child-Like Joy of Sharing

   Bonobos retain juvenile traits related
   to tolerance and cooperation.
            Image: Vanessa WoodsHow many times as a kid would your parents tell you to grow up and act your age? It turns out that not acting our age may be the very reason why we're so successful as a species.

Brian Hare and colleagues have just released a video (see below) showing a bonobo juvenile voluntarily helping another individual out of their cage to share a few delicious treats. In their study, to be released March 8 in Current Biology, the Duke researchers wanted to see if bonobos would choose to share with an unrelated individual even if they didn't have to.

Bonobos have long intrigued researchers for their unusual (except for us) propensity to cooperate and share with others, a trait not found to the same degree in our close cousin the chimpanzee.

According to a review of the study in Science Daily:

The test subjects had the opportunity to immediately eat the food or to use a "key" to open a door to an adjacent empty room or a room that had another bonobo in it. The test subjects could easily see into the adjacent rooms, so they know which one was empty and which was occupied.

"We found that the test subjects preferred to voluntarily open the recipient's door to allow them to share highly desirable food that they could have easily eaten alone -- with no signs of aggression, frustration, or change in the speed or rate of sharing across trials," explains Dr. Hare. "This stable sharing pattern was particularly striking since in other, nonsharing contexts, bonobos are averse to food loss and adjust to minimize such losses."

In an earlier study by Hare, Victoria Wobber and Richard Wrangam in last month's edition of Current Biology, it was shown that bonobos may have retained juvenile characteristics related to tolerance that don't exist in chimpanzees. According to the researchers, selection for reduced aggression may have resulted in bonobos retaining a host of traits related to juvenility that are all genetically linked. Higher levels of tolerance, delayed development of social inhibition and a skull that doesn't exhibit as many morphological changes in adulthood could all be related to a similar cluster of genes. In this network approach to evolutionary change, a single selection pressure could inadvertently effect numerous traits at the same time because other genes get pulled along in a case of genetic hitchhiking.

This would explain why adult bonobos, like humans but unlike chimpanzees, resemble their juvenile stage more closely and exhibit some of the most extreme forms of social bonding in mammals (with the eusocial naked mole rats in a totally different category). A lack of inhibition would also be consistent with both bonobos and humans showing some of the most inventive and spontaneous sexual behavior in the natural world.

As Wobber, Hare and Wrangham concluded in their study:

Understanding the evolutionary processes by which ontogenetic changes occurred in bonobos may provide insight into our own species' evolution. Herrmann et al. proposed that the crucial cognitive adaptation of humans relative to other apes is the accelerated development of social skills in infants. Although the genetic changes that produce such developmental shifts are not well understood, if we can determine the process by which the ontogeny of bonobos evolved, inferences can be made regarding analogous evolution in our own species.

Reference:

Wobber, V., Wrangham, R., & Hare, B. (2010). Bonobos Exhibit Delayed Development of Social Behavior and Cognition Relative to Chimpanzees Current Biology, 20 (3), 226-230 DOI: 10.1016/j.cub.2009.11.070