Science of Good and Evil

by Michael Shermer

  Figure 27. Comparative Brain Size

  Comparing the brain sizes of humans, primates, dolphins and porpoises, and other mammals reveals that there is a direct relationship between brain weight and body weight—in general, bigger bodies take bigger brains to operate. However, when controlling for body size, there is still a powerful trend showing that humans, primates, dolphins, and porpoises have larger brains for their body weight than all other mammals. In addition to their capacity for symbolic language and their ability to pass the mirror self-recognition test for self-awareness, this is powerful data in support of granting these species basic liberty rights. (From John M. Allman’s Evolving Brains, 1999. Courtesy of John Allman)

  Applying the ask first principle is difficult with nonhuman animals, of course, but as a thought experiment, it is a reasonable means of approximating what an animal might think about what you are contemplating doing to it. (Although I’d bet dollars to doughnuts that if you taught Washoe, Kanzi, Koko, and Chantek the sign for electric shock, and then asked them with sign language if they would like to receive one as part of an experiment, you would very quickly receive an answer.) We cannot ask a chimpanzee how she might feel if we lock her up in a small, cold stainless steel cage for the rest of her life in order to inject her with various human diseases, but we can observe her nonverbal communication, and, for most chimps, it is abundantly clear that they are none too pleased about such arrangements (as in the title of Wise’s first book, Rattling the Cage). In regard to the happiness principle and the liberty principle, as a first step toward a higher moral principle, we should never seek happiness and liberty when it leads to a great ape’s or a great marine mammal’s unhappiness and loss of liberty. For chimpanzees, bonobos, orangutans, and gorillas, this may mean nothing more than the freedom to go hunting and foraging for food in an open natural environment and to be protected from poachers who kill them for the “bush meat” market. For dolphins, this may just mean the liberty to swim in social bands throughout the planet’s oceans, free from tuna fishermen who drown them in their extensive fishing nets. It’s that simple. Don’t kill ‘em. Don’t eat ’em. Don’t wear ’em. Don’t cage ’em. Just let ’em be.

  To many animal rights activists, this proposal will seem cowardly in its timidity. To many anti-animal rights activists, this proposal will seem ridiculous in its grandiosity. It is, I think, the moderation principle in practice. If we adopt the historian’s stock in trade, deep time, I think it is a provisionally moderate moral step up the Bio-Cultural Evolutionary Pyramid, expanding our sentiments to include, first, more people and then more species into our circle of sympathies that will ultimately lead us toward the bioaltruism that will one day save our biosphere and, as a consequence, our species.

  Cicero’s Warning

  For all of humanity it has been a long journey on the evolutionary and historical pathway to where we stand today, on the brink of triumph or disaster, survival or extinction. Which road we take depends on which moral choices we make. Since we have the capacity for both moral and immoral actions, and the freedom to choose, our destiny lies within.

  In the first century B.C., the Roman statesman Cicero remarked, “Although physicians frequently know their patients will die of a given disease, they never tell them so. To warn of an evil is justified only if, along with the warning, there is a way of escape.” As we shall see in the last chapter, there is an escape from our immoral disease.

  8

  RISE ABOVE: TOLERANCE, FREEDOM, AND THE PROSPECTS FOR HUMANITY

  Nature, Mr. Alnutt, is what we were put in this world to rise above.

  —Katharine Hepburn to Humphrey Bogart

  in The African Queen, 1951

  In an episode of the original series of Star Trek, the Enterprise crew encounters an alien civilization playing a war game that is just about to escalate into a full-scale conflict. Captain James T. Kirk tells the alien leaders to “just say no” to war. Though instinctive, war may be resisted. There can be peace.

  ALIEN: There can be no peace. Don’t you see? We’ve admitted it to ourselves. We are a killer species. It’s instinctive. It’s the same with you.

  KIRK: All right, it’s instinctive. But the instinctive can be fought. We are human beings with the blood of a million savage years on our hands, but we can stop it. We can admit that we are killers but we’re not going to kill … today. That’s all it takes—knowing that you’re not going to kill … today. 1

  Are we, by nature, a killer species? The scientific evidence we have surveyed in this book answers in the affirmative. Built into our makeup is the capacity for aggression, violence, and war. Providentially, the scientific evidence also points to a solution. The rise of state societies, and with them the development of codified moral systems—initially through religious organizations and subsequently through secular institutions—have truly “civilized” our species, accentuating the moral and attenuating the immoral sentiments. We have done well, but we can do better. Our moral and immoral natures are in delicate balance. Too many immoralities confront us daily, even in the most civilized of cultures. Homicides and genocides, wars and revolutions, rape and domestic violence make their appearances too frequently on the nightly news. We still retain the power to trigger our own extinction, whether through ecocide with the mass destruction of our environments or through genocide from nuclear, chemical, and biological weapons. If nature put us into this world, how best shall we rise above it? In this final chapter on the prospects for humanity, we shall examine the evidence that our species is on a long evolutionary trajectory toward greater amity toward members of our own group, a long historical path toward more tolerance and inclusivity, and a long political path toward more liberties for more people in more places, whether they are members of our group or not. Out of this analysis arise two recommendations, one on individual tolerance and the other on social and political freedoms.

  The Domesticated Primate

  UCLA evolutionary biologist Jared Diamond once classified humans as the “third chimpanzee.”2 Genetically we are very similar, and when it comes to high levels of between-group aggression, we also resemble our ape cousins. But in comparing ourselves to other species of great apes, there is hope for humanity. In looking at within-group levels of aggression, it turns out that we are much more like bonobos, who are well known for their peaceful and loving ways. Once classified as “pygmy chimpanzees” because of their diminutive skulls, bonobos are now placed in their own grouping, primarily based on these dramatic behavioral differences from chimpanzees. We are much more peaceful than chimpanzees with our fellow in-group members, and our prodigious sexuality is far more like that of bonobos than chimpanzees. Although humans still exhibit within-group violence—as witnessed on the nightly news—compared to chimpanzees, who almost daily exhibit uncontrolled outbursts of male on male aggression, and male on female violence, statistically we are closer to bonobos than to chimpanzees. Domestic violence among humans, for example, while still at unacceptable levels, is nevertheless significantly less than that seen in chimpanzee families.3

  What are we to make of this contrast between humans as within-group bonobos and humans as between-group chimpanzees? Anthropologist Richard Wrangham proffers a plausible theory that as a result of selection pressures for greater within-group peacefulness, humans and bonobos have gone down a different behavioral evolutionary path than chimpanzees. That difference may be witnessed in morphology. The “pygmy chimpanzee” moniker was given to bonobos because, compared to chimpanzees, their skull, jaws, and teeth are much reduced in size, even while their other body parts are quite similar. It has been observed that when artificially selecting for docility in wild animals, along with far less aggression, breeders also cause a suite of other changes, including and especially a reduction in skull, jaw, and teeth size. This is called pleiotropy, in which a single gene may affect a series of traits. Selecting for one set of traits (for example, nonaggression) may generate other unintended changes (for example,
reduced skull, jaw, and teeth size). The most famous study on selective breeding for domesticity in wild animals was begun in 1959 by the eminent Russian geneticist Dmitri Belyaev at the Institute of Cytology and Genetics in Siberia (and continues today by Lyudmila N. Trut). Silver foxes (Vulpes vulpes) were bred for friendliness toward humans (defined by a series of criteria, from the animal allowing itself to be approached, hand fed, petted, to it actively seeking to establish human contact). In only thirty-five generations (remarkably short on an evolutionary time scale), the researchers were able to produce tail-wagging, hand-licking, peaceful foxes. What they also fashioned were foxes with significantly smaller skulls, jaws, and teeth than their wild ancestors.

  Similar changes can be seen in comparing domesticated dogs to their ancestral wild wolves. Mitochondrial DNA sequence evidence places the ancestor of every dog on earth, including New World dogs, to a single population of Asian wolves active roughly 15,000 years ago. In addition to smaller skulls, jaws, and teeth, domesticated dogs evolved a set of social-cognitive abilities that enable them to read human communicative signals indicating the location of hidden food. These abilities are not shared by their wild forebears nor by any of the other great apes. Specifically, domesticated dogs were able to pick the right container of concealed food when the experimenter looked at, tapped, or pointed to it, whereas wolves, chimpanzees, and other primates are unable to do so. Such nonverbal communication skills are vital for both domesticated dogs and domesticated humans.4 There were additional pleiotropic effects in the foxes. After several generations of breeding, for example, the foxes, like their canine cousins, began exhibiting floppy ears, curly tails, and striking color patches on their fur, including a star-shaped pattern on the face similar to those found in many breeds of dogs.

  What is going on here? The Russian scientists believe that in selecting for docility, they inadvertently selected for paedomorphism, or the retention of juvenile features into adulthood, such as floppy ears (found in wild pups but not in wild adults), the delayed onset of the fear response to unknown stimuli, and lower levels of aggression. It seems that the selection process led to a significant decrease in levels of stress-related hormones such as corticosteroids, which are produced by the adrenal glands during the flight or fight response, as well as a significant increase in levels of serotonin, thought to play a leading role in the inhibition of aggression. Curiously, in selecting only for docility, the Russian scientists were also able to accomplish what no breeder had done before—increase the length of the breeding season.5

  Wrangham suggests that over the past 20,000 years, as humans became more sedentary and their populations grew, there was selection pressure for less within-group aggression, and this effect can be seen in the reduced size of our skulls, jaws, and teeth (compared to our immediate hominid ancestors), our year-round breeding season and more bonobo-like prodigious sexuality, and our paedomorphism (see figure 28). Wrangham also cites research that shows how area 13 in the limbic frontal cortex in humans, believed to mediate the inhibition of aggressive behavior, more closely resembles in size the equivalent area in bonobos’ brains than it does that in chimpanzees’ brains.6

  Figure 28. The Paedomorphic Primate

  Paedomorphy is the retention of juvenile features into adulthood. Humans, like bonobos and domesticated dogs and foxes, show paedomorphy of the skull, jaw, and teeth. This illustration shows the growth of a chimpanzee skull (left) from juvenile (top) to adult (bottom), compared to the growth of a human skull (right), from juvenile (top) to adult (bottom). The chimpanzee skull matures very differently than the human skull. We are the paedomorphic primate. (From John M. Allman, Evolving Brains, 1999. Courtesy of John M. Allman)

  An additional test of this hypothesis is to compare serotonin levels in humans with those in chimpanzees and bonobos. The prediction is that human serotonin levels should more closely match those in bonobos. This comparison has never been made, but as Robert Sapolsky, a Stanford University biologist who studies aggression in primates, told me: “Overall, the literature shows that low levels of serotonin, or serotonin breakdown products in the cerebral spinal fluid, is a predictor of aggression, impulsivity, disinhibition, and so on. It probably has much to do with indirectly inhibitory roles that serotonin plays in the frontal cortex.” Paul Zak, an expert on the effects of oxytocin on cooperation and the control of aggression, agreed with Sapolsky’s assessment, and added: “Oxytocin (OT) is a feel-good hormone and we find that it guides subjects’ decisions even when they are unable to articulate why they are acting in a trusting or trustworthy matter. I think the same ‘sense’ of right and wrong in moral dilemmas may utilize OT.” As for the difference between chimpanzees and bonobos, Zak suggested that “there is evidence that serotonin (5HT) increases the release of OT. I would speculate that bonobos have higher OT (due to the frequency of sexual activity and touching) and therefore generally higher 5HT and less aggression (though I have not seen such a study done).” He also noted that in his lab they have been studying what he called oxytocin’s “ugly cousin,” “the neuroactive hormone arginine vasopressin (AVP), which is strongly related to reactive aggression in mammals, including humans.” Where does all this happen in the brain? Sapolsky suggested that the inhibition of aggression is ultimately controlled by the frontal cortex, of which we have plenty, chimps have some, and the baboons he studies on the Serengeti Plain of Africa have very little. “Baboons are far less disciplined than chimps, and when you map their brain anatomy you notice that they don’t have a whole lot of frontal cortical function. Even though there are tremendous individual differences among the baboons, they’re still at this neurological disadvantage, compared to the apes, and thus they typically blow it at just the right time. They could be scheming these incredible coalitions, but at the last moment, one decides to slash his partner in the ass instead of the guy they’re going after, just because he can get away with it for three seconds. Their whole world is three seconds long.” To the extent that morality is linked to impulse control and the delay of gratification, if there is a moral module in the brain, it is either in the frontal cortex or directly linked to it and is heavily mediated by brain chemistry and experience. Zak noted, for example, that in mice that are predisposed to have high levels of oxytocin, if they are deprived of maternal nurturing, “a large proportion of brain areas with OT receptors atrophy.”7

  These data fit well with the theory on the evolution of the moral sentiments presented in the first half of this book. The increased size of our brains, particularly the frontal cortex, gave humans a cognitive advantage over other primates that allowed us to better control our impulsive emotions and delay gratification, as well as form social coalitions and plan strategies. Between-group competition (with other hominid and primate groups) for limited resources led to the selection for such immoral sentiments as competitiveness and selfishness, but at the same time it led to within-group cooperation and selflessness that enhanced the fitness level of individual members of the group. The result is within-group amity and between-group enmity (figure 29).8

  This evolutionary scenario bodes well for our species. Even though the behavioral potential for between-group violence exists in our primate brains, we also harbor the seeds of peaceful coexistence. We cannot increase the size of our frontal cortex. However, we can learn to be moral. (Children do it—the frontal cortex is not fully developed until well into the teenage years, which is why children are, in a manner of speaking, premoral animals, why teens seem so impulsive, and why parents discipline their children in an attempt to shape a moral sense into them.) We can also practice being moral. If making love makes more oxytocin, and more oxytocin means less aggression, then there very well may be a neurological correlate to the cliché, “make love, not war” (figures 30 and 31). We can also learn to think differently about ourselves—perceiving the entire human population as a single group, for example, would eliminate between-group aggression. Although recent history is not encouraging, the long-term tre
nd over the past half millennium has been toward greater inclusiveness and more liberties, for more people, in more places. There are two ways to reinforce the continuation of this positive trend: (1) individual action to accentuate tolerance and attenuate intolerance of individual differences between people; (2) political action to expand whom we tolerate, both legally and morally, to be members of our in-group.

  Figure 29. The Domesticated Primates

  An orangutan, bonobo, gorilla, and human are pictured. In measures of between-group violence, humans are more like aggressive and territorial chimpanzees. In measures of within-group violence, humans are more like peaceful and loving bonobos. Between-group competition for limited resources led to the selection for within-group cooperation and selflessness and between-group competitiveness and selfishness. (From Adolph Schultz, The Life of Primates, 1969. Courtesy of Orion Publishing Group, Inc.)