Jan 07 2010
“The behavior of bonobos, unfortunately, is much less well known than that of chimps, and further study might reveal a darker side to their natures.” – Paul Ehrlich (19)
Compared to gorillas and chimpanzees, bonobos have some physical proportions that suggest movement toward the human. For example, their skulls are smaller to overall body size.(20) Do bonobos likewise have behavioral traits that suggest movement away from the more ‘barbarian’ ape toward the more ‘civilized’ human? While a number of people have described the bonobo as a relatively egalitarian ape (an early form of the liberal democrat?), many recognize some of the factors, rather than an innate goodness, that contribute to the behavioral differences we describe as more egalitarian.
Frans de Waal, in Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are, says this about the bonobo: “They are better described as tolerant than egalitarian.”(21) In his book about the roots of human egalitarian behavior, USC biological anthropologist Christopher Boehm recognizes that the strength of female coalitions ‘puts a lid on’ the heirarchical strivings of male bonobos.(22) Lacking the strong female coalitions, how would the males behave?
Besides the above question, and pertinent to it, is it possible that our limited understanding of bonobos has misled us? In Human Natures: Genes, Cultures, and the Human Prospect, Ehrlich noted,
“Although bonobos are not as well studied as chimpanzees, we do known that there are also many aggressive interactions among males of that species. Individuals hit, bite, slap, shove, grab, and otherwise abuse one another and use a variety of bluffing and charging displays. Aggression by a dominant male is countered with various submissive reactions by lower-ranking males, including appeasing the aggressor by permitting him to mount.” (23)
Hmm. Maybe bonobos aren’t all that different from chimpanzees. Has the positive been accentuated to a degree that distorts? Besides all the seemingly friendly sex and lack of a preeminent male dominance structure, bonobo males do threaten one another by glaring and gesturing, as they also make submissive signs via hand-extension and prostrations. (24)
Perhaps the observed behavioral differences between chimpanzees and bonobos is not so much about their innate nature as it is about differing environments. Maybe both the chimp and the bonobo are somewhat like Swiss Army knives (less so than humans, of course), and their evident “nature” will change along with local conditions. Two naturally manipulated variables that confront the bonobo, and likely shape its behavior, are likely key to their relatively placid demeanor.
In bonobos, female ovulation is more concealed. (Is this an environmental factor? For the males it is.) Does this fact play a role in an equalizing of the power dynamics between the sexes? Is this one of the reasons why a bonobo alpha female is apparently as dominant as the alpha male? It very well could be. For, as Freud speculated in his theorizing about the centrality of libido to human behavior — for without procreation and the desire for it, this is no human — sex is extremely important to animals. With concealed ovulation comes lesser opportunity and incentive for males to fight over, guard, and “possess” females as a resource when they are visibly fertile.
Yet even with sex relatively crossed out of the equation, bonobos do display hierarchical behaviors. In fact, bonobos display more fighting and dominance behaviors than chimps around food.(25)
Besides reproduction, what resources do primates fight over? Food might be the second most important resource and something worth battling for. Robert Wrangham speculates that a key environmental difference for the bonobo — one that has shaped their behavior in the short and long terms — is the absence of gorillas in bonobo forests. This absence may have made foraging for foliage foods easier and less dangerous. Is this, too, partly responsible for the seeming diminished aggressiveness of male bonobos? But what of the “more fighting” around food mentioned above? Are in-group skirmishes something distinct from out-group aggressiveness?
Wrangham writes, “The idea that selection for reduced male aggressiveness produces bonobo-like features is supported by data on domesticated mammals.”(26) The bonobo male: more puppy-like than the chimpanzee?
Aha! What are humans but upright apes that retain many juvenile characteristics? (It’s called neotony.) Good question. There is one thing I think we can be fairly confident about, however. Neither the chimpanzee nor the bonobo provides a perfect glimpse into our behavioral past.
(19) Ehrlich, P. R., Human Natures: Genes, Cultures, and the Human Prospect, Island Press, Washington, D.C., 2000, p. 210
(20) Wrangham, R. & Pilbeam, D., “African Apes As Time Machines,” in Galdikas, B. M. F., Briggs, N. E., Sheeran, L.K., Shapiro, G. L. & Goodall, J. (Eds.), All Apes Great and Small, Volume I: African Apes, Kluwer Academic / Plenum, New York, 2001, p.13
(21) de Waal, F. Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are, New York, Riverhead Books, 2005, p. 84
(22) Boehm, C., Hierarchy in the Forest: The Evolution of Egalitarian Behavior, Harvard University Press, Cambridge, MA, 1999, p.30
(23) Ehrlich, P. R., 2000, p. 206
(24) King, Barabara, The Dynamic Dance: Nonvocal Communication in African Great Apes, Harvard University Press, Cambridge, MA, 2004, p.163
(25) Boehm, C., Hierarchy in the Forest: The Evolution of Egalitarian Behavior, Harvard University Press, Cambridge, MA, 1999
(26) Wrangham, R. & Pilbeam, D., 2001, p.12