Wednesday, February 10

Those childish bonobos

Developmental delay may explain behavior of easygoing bonobo apes

ScienceDaily (2010-01-29) -- New research suggests that evolutionary changes in cognitive development underlie the extensive social and behavioral differences that exist between two closely related species of great apes. The study enhances our understanding of our two closest living relatives, chimpanzees and the lesser-known bonobos, and may provide key insight into human evolution. ... > read full article

For years, I was not particular gungho about developmental psychology. Developmental neurobiology has some pretty neat genetics in it, like Robo, but you're still talking about just one gene in just one part of the brain during just one part of the organism's lifespan. Also these genes have been observed in fruit flies, not Bongo Jones at the San Diego chimp enclosure.

Anyway. Developmental psych becomes much more interesting when you consider the mental capacities that develop during childhood, most notably theory of mind. Apes have incomplete theories of mind, and some would say that an eight year old child mimics the behavior of an adult chimp quite effectively. Children happen to be easier to study because there are more of them, they can usually communicate verbally, and you potentially have access to the complete development of the human theory of mind, which might just replicate our extinct ancestors' development of this theory of mind. While not always true, "ontogeny recapitulates phylogeny" remains a powerful principle.

What do these findings mean for primatology? If bonobos are more "juvenile" it could mean a less developed theory of mind, among many things. There is already some evidence to suggest this is the case. While the three chimpanzees (human, bonobo, chimp) are more closely related to each other than other apes, there remain limitations on how accurately we can assess relatedness. This might mean that chimps are significantly more related to us than we are to bonobos, or it could be an example of convergent evolution.

I was pleased to see this research is supervised by both Richard Wrangham and Brian Hare. I'm a big fan of both their work. The studies were performed in sanctuaries in Congo, not zoos, which I have been lead to believe (by Gottfried Hohmann), leads to better results. Hohmann mostly does impressively challenging work with free ranging bonobos in Congo, but he mostly studies behavioral ecology, not cognition.

In conclusion, please note that the "blog copy" function of ScienceDaily doesn't work on either Firefox or Chrome. So of course I used ... Opera.


  1. Humans and chimps diverged 5-7 million years ago. Chimps and bonobos split only 1.5-2 million years ago. While these times may be somewhat tricky to estimate, there is little doubt the chimp/bonobo lineage divereged from humans well before the pan genus differentiated itself into two species. In fact, the divergence is sufficiently recent that we can identify with reasonable certainty the geographic feature responsible for separating common chimpanzee and bonobo populations: the Congo river.

  2. Ah, my language on who could be more closely related to who was a bit unclear - I've fixed it now.

    And yeah, the congo river dealie is pretty neat.