| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Letters to the Editor Bonobo’s bluff I am always delighted to see articles about apes, particularly when they feature the elusive bonobo, and address issues concerning human evolution in the clear and engaging way that Dr. Jablonski has done. However, there are a few points that I feel require further clarification. Jablonski writes “...traits that [bonobos] do not share with common chimps must have evolved in parallel to the human lineage.” This overlooks the more parsimonious explanation that traits shared by humans and bonobos were present in our last mutual ancestor, but the common chimps took a different route after their lineage diverged from that of bonobos. In her discussion of threat displays as a component of aggression avoidance, it seems that Jablonski distinguishes between the prop-enhanced charging bluffs of common chimpanzees and the sexual interactions of bonobos. Interestingly, the photos chosen to illustrate this section include a bonobo displaying with a branch. The bonobo’s bluff, while perhaps less overtly aggressive-seeming than the common chimpanzee’s, can be quite impressive. When a male bonobo drags a fully-leafed, four-meter-long branch across your path in a locomotive rush over the forest floor, he has your full attention. Trust me. The distinctions between bonobo and chimpanzee behavior are often over-emphasized. This may reflect how little we know of bonobo behavior in the wild, compared to their more common cousins. As the range of the bonobo is confined to the borders of the Democratic Republic of Congo, bonobo field observation is incredibly difficult. Between the political instability of their habitat country and the threats of poaching and logging, we may loose these cousins before we ever really get to know them. I hope that you continue to feature work on bonobos and other apes to remind the public of their peril.
Michelle Merrill, Aptos, California Nina Jablonski responds: I was very happy to read Michelle Merrill’s response to “The Three Chimpanzees,” especially the comments she had on aggressive behavior in male bonobos, based on a what sounds like an “up-close-and-personal” encounter in the field. It was unfortunate that the branch-wielding animal depicted in the article was actually a bonobo, not a common chimp (don’t blame the author for this; I didn’t see the photos before publication), but this confirms Merrill’s observations about bonobos packing more of a punch than we often given them credit for. My one point of disagreement with her is her statement that suggests that the aggression-mitigating traits shared by humans and bonobos (but not by common chimps) were shared by “our last mutual ancestor, but the common chimps took a different route after their divergence....” What humans and bonobos share is that both have highly efficicacious means of avoiding and mitigating aggression. These means are very different—bipedal displays leading to habitual bipedalism in the case of humans, tension-reducing sex in the case of bonobos—and they evolved independently. The very point of the article is that in all three chimps, different strategies for reduction of aggression and violence have evolved from a common ancestor which shared the basic “template” of the bipedal threat display. Finally, by way of a small correction, I should also point out that in the figure showing the cladogram of higher primate relationships, the clade on the far left should have been labeled “Old World Monkeys,” not “Old World Apes.” At Your Surface The caption for the photograph on page 28 (Summer 2002) refers to “vertical services.” Are they similar to “vertical surfaces”? California Wild is a great magazine. Lester H. Lange, Capitola, California Editor: In this case, remarkably similar. |