One day, two adult males were introduced after a long separation. They both screamed and turned around each other for six minutes without any physical contact. We feared a bloody confrontation (most animals fight when introduced to a relative strangers of the same sex), but Kevin, the younger male, kept stretching out his hand, and flexing his fingers, as if beckoning Vernon to come closer. Occasionally, Kevin shook his hands impatiently. Both males had erections, which they presented to each other with legs apart, in the same way that a male invites a female for sex. It was as if each male wanted contact but did not know whether the other could be trusted. When they finally did rush towards each other, instead of fighting, they embraced frontally with broad grins on their faces, Vernon thrusting his genitals against Kevin’s. They calmed down right away and happily began collecting the raisins
Bonobos have sex in virtually any combination - males with males, females with females, and males with females. Juvenile male bonobos even perform fellatio on each other. About the only sexual pattern you don’t see is incest. But it is the sex between females that makes bonobo society really tick. Female bonobos form very strong alliances with each other, reinforced with frequent genito-genital rubbing (GG rubbing). The upshot is that bonobos are a female dominated society, one of the few such societies in the animal kingdom. That is even more surprising because male bonobos are about 15% larger than females and have sharp canine-like teeth. Individually the male bonobos should be able to dominate the females, but the females form stronger and more cohesive groups which give them the power. Females use that power to control the food. Male bonobos can only get food by begging from the females.
Chimps are notoriously violent and warlike with their neighbors but bonobos are peaceful. Once again this happens because of the use of sex as a social lubricant. It begins with the females. They will inspect each other and engage in GG rubbing with each other. They will also begin to have sex with males from the other group. This paves the way towards both groups peacefully coexisting, at least for the brief periods of time (bonobo males never get along with each other).
Why are bonobos so unique? The entry point to understanding the bonobos is their unique solution to the problem of infanticide. Consider langur monkeys. When a male langur monkey takes over a harem of females he will promptly kill all the infants. At first biologists were stunned by this discovery. They considered it an aberration, a pathology. Biologist had internalized the false idea that evolution works “for the good of the species.” Sarah Blaffer Hrdy had the correct explanation. Infanticide brought the females back into a fertile cycle sooner. That meant that the new alpha male could procreate sooner and ultimately have more offspring. Over time the infanticidal langurs would outbreed the moral langurs who did not commit infanticide. The discovery of infanticide in langur monkeys initially shocked biologist, but it has since been seen in many species including lions, bears, and prairie dogs, and of course, human beings (see Homocide by Daly and Wilson).
Infanticide takes us to one of the most important lessons of sociobiology: males and females have some pretty horrible strategies that they use to maximize their reproductive self-interest at the expense of others. Dominant males who commit infanticide maximize their reproductive fitness at the expense of females and their children. But the bonobo females have an excellent counterstrategy: disguised fertility. The labia and clitoris of female bonobos swell to the size of a smallish soccer ball. Female chimps only have these swellings when they are fertile, but bonobo females have frequent fake swellings even when they are not fertile. These fake swellings, combined with the bonobo’s promiscuous sexuality, disguise the paternity of bonobo infants. Bonobo males do not commit infanticide because they don’t know which offspring are their own.
Chimpanzee females do not disguise their fertile cycles with fake swellings. This means that at any given time there may be only a couple female chimps which are fertile. That creates a competition between the males. The stakes of this competition are sexual access to the fertile females. An alpha male can copulate with the swollen females and driving his weaker rivals away. What are the beta males supposed to do – give up on life? Of course not. Chimps are an intelligent and social species. The beta males can play what Frans de Waal appropriately dubbed ‘chimpanzee politics.’ The beta male chimps do not have to concede defeat; they can team up with other males and depose the existing alpha. The leader of the team becomes the new alpha. But he only reached that position because he relied on teamwork. Without that alliance his reign will be short-lived. That means he has to allow his partner at least some sexual access to females. This dynamic makes male chimpanzees both competitive and cooperative. Male chimpanzees are surprisingly adept at cultivating alliances and rewarding their friends. Machiavelli would be proud.
The key point that makes chimpanzee politics possible is that it is relatively easy to monitor the small number of females who are fertile because they have visible swellings. Bonobo females have fake swellings which disguise fertility. That one seemingly innocent difference undermines the foundation of the male-dominated society. It is relatively easy for the alpha chimps to control sexual access to the one or two females who happen to be swollen at a given time. It is much more difficult to control sexual access to females if four or five are swollen at a time. Despite the alpha’s best efforts, his rivals will manage to copulate fairly regularly.
Think of it in terms of risk and reward. The risks of fighting a struggle for dominance remain as high as ever. Male chimps are frequently killed playing chimpanzee politics. But the rewards are much lower because alpha males won’t be able to control sexual access to females to the same degree. The desire to achieve sexual dominance is what drives the alliances between the chimpanzee males. Bonobo males don’t have the ability to do this, which means that they do not have the same degree of social skills as chimpanzee males. On the other hand, bonobo females are extremely adept at forming alliances. They fill the power vacuum quite easily.
Alliances let bonobo females take control over both the food sources and their own sexuality. Although bonobos are promiscuous they do have favorites and sometimes refuse the advances of unwelcome males (we’ll have more to say about this later). So does female dominance mean that we are trading in one problem for another? Not necessarily. Female dominance is much more egalitarian. Bonobo females can only have one offspring every four or five years. They cannot do much to maximize their reproductive fitness above this baseline. That in turn means that female bonobos do not have an incentive to make the despotic power plays that you see in the male-dominated chimpanzee world.
That does not let female bonobos off the hook. They still have their power plays. Female dominance basically boils down to two things. The first is securing a larger share of the groups food supply for her offspring. This is an aspect of the “big mothers” theory. In cooperative species the high status females can take an unfair share of the group’s resources for her own offspring. Mature female bonobos who have years of grooming and GG-rubbing with the other females are embedded into dense social networks. They use that power to benefit their offspring. The second tactic is to use their social status to enhance the reproductive opportunities of their sons. Bonobo females form lifelong attachment to their sons and these males derive much of their social rank through their mothers. The sons of high ranking females get more food and more sexual access to females than the offspring of low ranking females. Even though bonobo males will never dominate their group like their chimpanzee counterparts, they do manage to keeper the low status males away from females. De Waal explains (The Forgotten Ape, p.117,120).
There is a sharp decline in sexual involvement during a male’s adolescence due to the tendency of dominant males to occupy the core of the traveling parties, where the females are. Only when they enter adulthood and rise in rank do males regain access to receptive females. Not that male bonobos are egalitarian with respect to sexual privileges. In contrast to its peaceable image, the species conforms to the general patterns in the animal kingdom of male competition for females. Bonobo males may compete less fiercely than chimpanzee males, but a recent report from Wamba leaves no doubt that dominant males mate more often than others. Since the two top-ranking males in any traveling party generally do most of the mating, it is assumed that they suppress the sexual activity of other males.
Despite all its bohemian appeal, bonobos do not have a good social arrangement for modern societies based on providing children intensive cognitive stimulation and rich emotional support. All non-monogamous society suffer from the same fatal flaw: sperm are cheaper than eggs. That means females have no incentive to choose sexual partners based on warmth, gentleness, or ability to be a good provider for their offspring. Instead they are free to choose to fittest, most dominant alpha male. Similarly, males have no incentive to cultivate these sensitive qualities. Instead they will try to develop their sexual dominance (or “game” as modern humans tend to put it) as much as possible. The second problem is that once we have that developing sexual dominance takes precedence over becoming a good provider for the family and investing time and energy into their children.
So what do the bonobos teach us? Ultimately they teach us to appreciate the human way. Our way of doing things – monogamy and abstinence – is more restrictive and takes more discipline. But it also leads to greater cooperation between males and more involved fathers who invest more heavily into their offspring. De Waal explains (Our Inner Ape, p.125)
The dilemma of how to engender cooperation among sexual competitors was solved in a single stroke with the establishment of the nuclear family. The arrangement offered almost every male a chance at reproduction, hence incentives to contribute to the common good. We should look at the human pair-bond, therefore, as the key to the incredible level of cooperation that marks our species. The family, and the social mores surrounding it, allowed us to take male bonding to a new level, unheard of in other primates. …
What makes the bonobos so appealing to us is that they have no need for any separation of these domains: they happily mix the social with the sexual. We may envy these primates for their “liberty,” but out success as a species is intimately tied to the abandonment of the bonobo lifestyle and to a tighter control over sexual expressions.
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