Barbara J. King

Friday Animal Blog

Female apes rule! (When it comes to tools)

October 15, 2010

In both my classes this term at William and Mary, we’re discussing evolutionary puzzles. In Evolution of Gender, we’ve been reading scenario after scenario that reconstructs human prehistory in terms of rigid sex roles: males did x, females did y. And guess who—in the majority of models—gets pride of place? Males hunt, males provision their families, males protect their females. The females stay put, eat the food given them, and reproduce. (Tanner and Zilhman’s women-the-gatherer model is an exception.)

Even in Richard Wrangham’s otherwise bright theorizing in Catching Fire published last year, female Homo erectus cook the males’ food and require protection by those males from food thefts (thefts carried out by, you guessed it, other males).

In Introduction to Biological Anthropology, we’ve been grappling with a separate conundrum. Although chimpanzees and bonobos seem equally intelligent, their patterns of tool-using patterns in the wild don’t. The undisputed rocket scientists of ape technology, chimpanzees fish for insects, crack open hard nuts with stone tools, and even spear smaller primates using long sticks. Bonobos do none of these things.

And now along comes an article (online) in the journal Animal Behaviour, written by Thibaud Gruber, Zanna Clay, and Klaus Zuberbuhler at the University of St. Andrews. It offers new information on both these questions. (Alert blog readers, yes, Zuberbuhler again! He’s too primate-prolific for words).

Gruber et al. outline patterns already known to primatologists: Chimpanzees’ tool use involves feeding, as my examples above indicate; bonobos’ tool use has more to do with social situations such as communication and play.

But bonobo tool-using is far less researched than chimpanzees’. Because of this, these scientists studied bonobo tool use at five captive sites: two in the US (San Diego Zoo and San Diego Wild Animal Park); one in the DRC (Lola ya Bonobo sanctuary), and two in the UK (groups at Twycross Zoo). Relying on these data plus data already published, tool-using patterns by wild and captive chimpanzees and wild and captive bonobos were compared.

For 52 tool-using behaviors, direct comparisons across these four categories were possible. The paper is chock-full of great information; to me the most striking findings are:

*Tool use in bonobos can be highly complex, cognitively equivalent to that observed in chimpanzees.

*Wild bonobos, however, stand apart: they use tools in far fewer contexts than either their wild chimpanzee counterparts or chimpanzees and bonobos living in captivity.

Either bonobo foods, then, simply don’t require tools for processing, or primatologists haven’t observed bonobos long enough to have fully recorded their tool repertoire. Gruber et al. decide it’s most likely that all four categories of apes in their study are cognitively capable of tool use, but in wild bonobos, the environment doesn’t select for its expression. (They write “the environment prevents this development,” but that phrase is awkward; it’s not a blocking of tool use so much as a relaxed selection for tool use.)

*Sex matters! Female chimpanzees are known as more accomplished tool users than males. These new data show that female bonobos are “more avid” tool users than males also, and use a larger diversity of tools.

In this regard, Lola ya Bonobo yielded striking results: “Females displayed a larger range of tools or tool-related behaviours during food acquisition and play than males, although both sexes used tools in all contexts apart from one.” This sex bias is no mere artifact of bonobos’ hanging around with humans at the sanctuary, because upon arrival both male and female bonobos are equally exposed to tool-using models.

Perhaps, instead, females of these species “have evolved more sophisticated tool skills owing to the higher nutritional demands of pregnancy and infant care,” as the authors put it. Important too may be the close mother-daughter relationship (close until, in the wild, the daughter transfers out of the community).

Female bonobos are famous for hypersexuality and genital-genital rubbing, and that’s cool. But now they join their chimpanzee sisters in being understood as cognitively savvy tool-users.

And with this enhanced picture from our closest living relatives, it becomes that much harder to put any faith in scenarios of male-provisioned-or-protected, helpless females in human prehistory.

Comments

  1. October 15, 2010 5:49 AM EDT
    Thanks for another fascinating entry, Barbara. The data that you discuss has made me think about how we (meaning scientist studying animals or just average humans interested in our fellow creatures) are often too caught up in pre-conceived ideas and think that an animal species behavioural repertoire is limited, set in stone and there for us to observe (as if on a window display) in its fullness. So, it is wonderful to see new research showing “new” behaviours in bonobos and basically coming to the conclusion that, if they don’t display these behaviours in the wild, is because they don’t need to. This is a good remainder of how flexible, creative and mysterious animals are. And we still have so much to learn from them.
    - Nacho
  2. October 15, 2010 10:52 AM EDT
    For interesting sf speculation on reversal of sexual roles the Chanur novels of C.J. Cherryh are fabulous and fun!
    - Melanie
  3. October 15, 2010 3:54 PM EDT
    I remember you showing us that in class! However, I had no idea that females used tools more avidly than their male counter-parts. Very interesting fact. Thank you for sharing this!
    - Yonsoo
  4. October 15, 2010 4:43 PM EDT
    Nacho, I wish I'd written that phrase about what animals do: "as if in a window display in its fullness..." That's exactly it. When I studied baboons in Kenya years ago, my goal (affected by my supervisers as I was a grad student) was to provide a profile of "the average baboon infant." I'm just stunned now by that kind of thinking in myself- that I could go for a year and work that out, as if there IS an average baboon! Well, we all live and grow. Melanie, thank you, I will put the Chanur novels on my growing list. Yonsoo, hurray!, a current student has written in. Thank you. The reported research is new as of Oct. 8th (just up online) but yes, I'm emphasizing more in my other class, on gender, the patterned primate differences by sex. It's extremely interesting to discover that both bonobos and chimpanzees have sex differences in tool use in the same direction.
    - Barbara J. King
  5. October 18, 2010 11:22 PM EDT
    It is excitng to read that bonobo females are showing such intelligence in comparison to males. I am curious about the reasoning behind these discoveries; whether or not it is nutritionally related or based on the social relationship between mother and daughter, like you state in your blog.

    I am really enjoying you Intro to Biological Anthropology class and hope to take you Primate Behavior course next semester.

    See you in class!
    - Kim M.
  6. October 20, 2010 5:35 AM EDT
    It is definitely interesting to read that female chimps and bonobo were more "avid" tool users. There are many theories similar to male provisioned- helpless female theories and some even claim that females had smaller brain than those of males.
    - Youjin

Selected Works

Nonfiction
Why are animals so irresistible to us? Why do we live with and care so deeply about them? From the famous "art caves" of ice-age Europe, to the ancient villages where animals were first domesticated, to stories of apes, whales, dogs, and cats doing fascinating things today, King weaves together a scenario about the animal-human bond that encompasses our past, present and future.
Can scientists discover a prehistory of religion just as they have traced the evolution of technology, language, and art? What does compassion in chimpanzees, or burial patterns in our human ancestors and Neanderthals, tell us about the origins of religion? In Evolving God, named a Top Ten Religion Book for 2007 by the American Library Association, Barbara King explores these questions.
How do chimpanzees, bonobos, and gorillas-- the African apes -- communicate using body postures and gestures? Using her many years of experience studying these apes, Barbara King answers this question in a book that offers a new perspective on the evolution of language.