The Full Spectrum

Let’s talk for a moment about the special status that humans have in the natural world — or rather, the special status that we often accord ourselves.   Though most people no longer think of the world in terms of Aristotle’s scala naturae, we still have a tendency to consider ourselves unique, separate from and far more advanced than the rest of the animal kingdom.  And it’s true that humans do lots of things that other animals don’t: we  build cities, we fly airplanes, we write books (and blogs) and create works of representational art.  As a species, our accomplishments are substantial.

But if there’s one thing that modern ethological research has demonstrated, it’s that many of our abilities and behaviors can be found at least to some extent in other species, especially in the primate family.  Since Jane Goodall’s early observations of tool use among wild chimpanzees at Gombe Stream National Park led her academic adviser, paleoanthropologist Louis Leakey, to comment that “now we must redefine tool, redefine man, or accept chimpanzees as human,” several once-vaunted hallmarks of humanity have been eliminated from the list of defining characteristics that separate Homo sapiens from other species.  Primatologists have provided evidence that chimps hunt, participate in campaigns of organized aggression toward neighbors, maneuver for status in Machiavellian ways, and reconcile following conflict.  Research on language use by great apes similarly suggests that in many cases the difference between humans and our closest relatives is one of degree rather than kind.

The existence of this behavioral spectrum  has been illustrated yet again in the new issue of the journal Current Biology, in which anthropologists Richard Wrangham and Sonya Kahlenberg report that young chimpanzees in Kibale National Park in Uganda carry and play with sticks in a manner similar to children with dolls.

chimpanzee-stick-doll

A female chimpanzee holds a “stick doll” between her leg and body. (Sonya Kahlenberg)

Examples of play among juvenile animals are not new.  But it is intriguing that these researchers identified a sex-based bias in their data: as in humans, female chimpanzees were more likely to carry stick dolls.  Does this mean that young females are simply practicing for the future by imitating the mothering behaviors they observe within a group?  Or might it suggest innate psychological differences between young male and female chimpanzees?  In either case, how do these data pertain to studies of sex/gender differences in humans? Nature/Nurture debaters, start your engines!!

Whatever the long-term implications of this new study, it serves to illustrate that the more we learn about the behavior of other animals, especially apes, the less reason we have to consider ourselves wholly separate from them.  Of course, this isn’t to say that you should expect to see orangutans in Indonesia building treehouse cities anytime soon.  But try not to be too taken aback the next time you read a story about a wild animal doing something “surprisingly” human-like.
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To read more about play-related sex differences in non-human primates, click here.  And don’t forget to subscribe to The Tinkering Primate if you want to get emails about new posts.  Just click the “Yes Please” button underneath the chimpanzee on the site banner.

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3 responses to “The Full Spectrum

  1. Best post yet.

  2. Fascinating! I wonder what this says about the fact that I carry around a stick doll too…

  3. Have they come to a decision yet? Are chimpanzees human? I think that makes the most sense. Redefinitions are so bothersome.

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