A postdoc working with Carter, Karen Bales recently completed work in voles meant to mimic the effect of giving autistic children a few squirts of oxytocin while they were young—and while the animals were young, the treatment worked as expected, making for warmer and fuzzier adolescent prairie voles. But as they aged, their behavior began to deviate from the norms of polite prairie vole society. That is, these same males had a hard time partnering up. Those early doses made them less, not more, social as adults.
Carter told us she thinks those early doses of oxytocin are, in effect, “downregulating”—that is, desensitizing—the normal receptors of those young voles. As they age, then, the receptors are less able to read normal levels of oxytocin.
And this is where her line of logic becomes at once deeply personal and near universal. Despite being the world’s go-to expert on oxytocin, Carter was treated pretty much like any other delivering mother in a hospital in Germany a generation ago. Back then, she told us, it was relatively rare for doctors to inject mothers in labor with the synthetic form of oxytocin, Pitocin—it happened in maybe 10 percent of deliveries. But she was injected.
“This concerns me a great deal, and it concerned me right from the start,” she said. “As a scientist, I wanted to know what I did to my baby by letting the doctor give me that, but I really didn’t have a choice.”
True, the doctors did not give the drug to the baby, but now we know that this same molecule shows up in the brain seconds after a mere mist of it is in the air, and a baby in utero is far more intimately connected to the source. Carter must think about this now, knowing as she does the results that showed up in those prairie voles only when they became adults. A very recent paper correlates an increase in the incidence of autism with receiving Pitocin during delivery. Carter says that Pitocin is routinely administered to delivering mothers in, she estimates, 90 percent of cases, although there are some signs that this practice is waning.
At the same time, the current spate of research has turned up some other drawbacks to this simplistic, medical-model approach to oxytocin and vasopressin—but these are as intriguing as they are cautionary. These findings open a window to some sobering realizations about evolution itself and our ability to comprehend its wisdom. They make us confront violence.
What one tends to remember and report from those early prairie vole experiments is that the neuropeptides in question provoked monogamy, bonding, and solid parenting—true enough. But Carter says it was also true from the beginning that once the adolescent male crossed the line of puberty in a chemical rush, he ceased to be a meek little field mouse. “He becomes a lethal weapon,” she said. “He fights off any and all intruders and will fight to the death at the same time he is the nurturing father and devoted mate.”
In its summary of research on oxytocin, Science magazine reported on a study in Amsterdam headed by Cartsen De Dreu that used a nasal dose of oxytocin and assessed the effects with a standard game that subjects played for money:
Compared with men who got a saline spray, those who sniffed oxytocin behaved more altruistically to members of their own team—but at the same time, they were more likely to preemptively punish competitors.… In a 2011 study in the Proceedings of the National Academy of Sciences, De Dreu’s team found that oxytocin increased favoritism toward subjects’ own ethnic group (native Dutch men) on a series of tasks and thought experiments done on a computer, and in some situations the treated men exhibited more prejudice against other groups (Germans and Middle Easterners, in this case).
This is a double-edged sword.
One goal of oxytocin research has been to promote desirable characteristics like trust, empathy, and loyalty, traits in short supply among us today. Yet we may want to place our assessment of “desirable” in context with a question that Carter put to us: if science could indeed deliver a pill that would make you a paragon of these very traits, would you take it?
And you need not think long to answer in the negative. That distrust of outsiders often leads to violence against those same people, and in evolutionary terms, violence is not necessarily a problem. Violence is useful and therefore adaptive; we need it to survive and always have. Even today, in situations where violence seems to be counteradaptive, it persists because in so many other situations it was critical to survival.
We did not get our first hint of this conclusion from biochemistry or even from evolutionary history. John Ratey has a long history of treating some exceedingly violent people, and a clear theme emerged in his practice, especially in dealing with domestic violence. The blowup and the violence in those situations (and this is not a trivial matter at all; by far, domestic violence is our most widespread form of violence in modern society) often come at a critical and common point: when the victim, the female, takes steps to leave an abusive partner. That threat triggers an irrational rage that quickly explodes—and it took time to see it, but it became clear to John that this explosion was defensive. The partner’s threat to leave was a threat to the home, and the violence—no matter how irrational or misplaced—was a defense of the home.
We are not arguing that this sort of violence is justified or even adaptive. It is, in fact, a failure of the brain’s coping mechanisms when faced with threat. The executive function of the brain in the frontal cortex gets hijacked in these situations, and violence ensues. It is irrational and pathological—but the wiring for it, the tendency, was put in place by evolution as an adaption. It is precisely the same impulse that sorts us into tribes, that causes us to feel best when in the circle of like-minded people we were born into and feel ill at ease when we are among others, maybe Ju/wasi, Masai, Apache, and Sarmatian once, now maybe Christians or Muslims, Republicans or Democrats, immigrants, operagoers, gardeners, bluegrass musicians, or the folks we know at the CrossFit gym. Distrust of outsiders is the flip side of the social bonding that allows us to trust those closest to us.
THE CORE HUMAN TRAIT
We deliberately entered this broader discussion of tribalism and violence through oxytocin because childbirth, nurturing, and bonding lie at the center of the human experience. Early in this book, we outlined the broad markers of human evolution and introduced this key point. Now it is time to revisit it in this new context.
We need only consider the cartoon image of cavemen in modern imagination to begin to understand our long-blinkered perception of the nature of our ancestors: in the cartoons, the caveman always carries a club. This is nothing more than an extension of the Hobbesian notion of nastiness, meanness, brutishness, et cetera, yet the notion is not limited to cartoons. Throughout paleoanthropology, there has been a persistent strain of imagining our species’ development as governed by violence. Much of this has been rooted in the study of bones, skeletal remains that show signs of breaks and stabs and beatings, and so people reading these bones from time to time interpreted this as a sign of constant warfare.
At the same time, our closest living relatives—even the comparably peaceful bonobo, but especially chimpanzees—show plenty of ability when it comes to violence, even warfare, and so this, too, is part of the state of nature. Further, we have seen it emerge in the inquiries of people like Carrier, who began by looking at our body’s adaptation for running but wound up concluding that we are equally adapted for and well suited to punching and throwing spears. Truly, violence is in our bones and muscle. This conclusion will not go away, evident also in the headlines of the day, the confirmation of hatred and carnage in our times and in all times. Indeed, the evolutionary psychologist Steven Pinker has argued that we in fact live in relatively peaceful times, and that the record shows the past has been characterized by stunning degrees of aggression toward one another far worse than today. He argues that a decline in violence is a benefit of civilization and that slowly humanity is learning to put this aside. We can only hope. Yet there are some lessons from evolution that may help us think about this most vexing of human dilemmas.
Pinker’s argument is data-based, and he a
rgues that it holds through all of human history—yet there is good reason to make the distinction that we have throughout this book: that the best evidence for our violent past comes from the past ten thousand years, a time when territory and ownership of land became vital, when farms supported cities, when monarchs could raise armies, and when we developed the tools for mass warfare. Much of the case that hunter-gatherers spent a great deal of time and energy killing one another is circumstantial at best. For instance, one analysis of the bumps and breaks on ancient skeletons—evidence earlier interpreted as resulting from warfare—got another look from researchers who found a close modern analogue to skeletons in this condition, and these were not the skeletons of warriors. The closest match to injuries like these in modern times were in rodeo cowboys, people who mix it up with big unruly animals for sport.
Some distinctions need to be drawn, and saying that primitive life was rough-and-tumble is not the same as saying it was violent.
It may help to be a bit more precise in our definitions. First, we would argue that hunting is not violence. It is killing, true enough. There will be blood. But the brain of the hunter is in a very different mode than the brain of a murderer or warrior. This is pretty clear-cut and demonstrable in measurable phenomena like brain waves. The hunter generally faces no threat that triggers a response of terror or aggression. Just the opposite, as we have seen on so many levels. The hunter is engaged, even empathetic. Indeed, through every bit of knowledge we have of hunting peoples—from the cave paintings in southern France to the rituals of plains bison hunters—comes evidence that these people regarded their prey with respect and awe.
Beyond, there seems to be a good case for separating out defensive violence against predators. Beating off lions and bears is not what we think about today when we discuss violence, yet fighting off predators probably was the form of fighting we knew best in evolutionary times. The threat of predation shaped us, and it had to, particularly the threat to our helpless infants. When we speak of violence as adaptive in evolutionary terms, this is the best example. This is why aggression is the flip side of the bonding powers of oxytocin; it is adaptive not only to cooperate and bond with our fellows but to protect and defend.
Yet none of this gets at aggression against other humans, and it should. Why does aggression persist beyond reasons for it? Why are we so riven with senseless killing and warfare? Is this simply who we are, as Pinker argues, and does this require the cultural evolution of civilization to gradually wear it away, wall it off to a silent corner of our gene pool?
Part of our thinking about human evolution has missed a great deal because we see what we want to see, and the caveman with the club is something of an icon in this regard. We are indeed fascinated by broken bones, spear points, and stacks of mutilated skeletons, yet much has been gained in reexamining the evidence from a different perspective. Put another way, the history of trying to understand human evolution has been beset with all sorts of debates about what defined us, what came first, and what is most important. Big brain? Opposable thumbs and use of tools? Fire? Fishing? In all of this there is an obvious bias toward things men do.
Yet one of the more thoughtful and interesting students of human evolution, the anthropologist Sarah Blaffer Hrdy, has told us much by reexamining the evidence in light of the things women do. In terms of evolution, her approach represents far more than correcting a gender bias. In evolutionary terms, the success of a species is completely dependent on reproduction—whether it goes on, and whether it fields a set of genes for the next generation. As we have said, Homo sapiens are unique in all the animal world, completely without precedent in one regard. No other species must spend as much time and energy rearing and protecting infants as we do. To Hrdy, this is the defining fact of our existence, and the term she uses is “cooperative breeding.” That is, we come together as a species to raise children: “What I want to stress here, however, is that cooperative breeding was the preexisting condition [emphasis hers] that permitted the evolution of these traits in the hominin line. Creatures may not need big brains to evolve cooperative breeding, but hominins needed shared care and provisioning to evolve big brains. Cooperative breeding had to come first.”
She is saying our cooperation and ability to bond to one another is primal, foundational, the bedrock. In her book Mothers and Others, she hits on the essence of this idea: “Brains require care more than caring requires brains.”
Still, the persistence of violence seems to contradict the importance of bonding, but then humans are nothing if not contradictions. And this contradiction teases out an even more basic issue of evolution—one that today’s evolutionary biologists debate at great length, but which has in recent years produced all sorts of insights into the forces that drive us. Much of evolutionary thought has rested on discussions of individual fitness, with an individual being a discrete unit of genes, and therefore the only unit on which evolution can act. Yet as studies of social animals (ants, termites, prairie voles, and humans) came to the fore, it occurred to thinkers that there was such a thing as group fitness. That is, the degree to which we were able to successfully cooperate and cohere as groups yielded clear advantages to our survival. This raised the idea of group rather than individual selection, a notion still hotly debated. And whether we know it or not, it is still hotly debated every day and every second in each of our brains. That’s because it is sometimes to our advantage to do what is good for us as individuals and other times to do what is best for the group—selfish behavior versus altruistic behavior. Both confer advantages in evolutionary terms, and we are wired to heed both sets of messages.
It’s best at this point to return to the evolutionary biologist E. O. Wilson: “The human condition is an endemic turmoil rooted in the evolution processes that created us. The worst in our nature coexists with the best, and so it will ever be. To scrub it out, if such were possible, would make us less than human.”
9
Central Nerves
How the Body Wires Together Health and Happiness
Let’s go back to the town house near Chapel Hill, North Carolina. Sue Carter’s husband, an intense-looking fellow, had met us at the door, introduced himself in a businesslike way, and retreated so we could talk with Carter. Later, there was a break in our conversation, and he was rummaging around in the kitchen, opening drawer after drawer, searching for the tamper for his espresso machine, a clear case of partner-based misplacement of crucial accessories.
“Sue puts things away, and I look for things,” he announces without preamble. “I’ve decided it’s all about the other person thinking you know exactly what they are doing. The problem is the interpretation of intent and whether the feedback from it modifies behavior.”
It’s not apparent that an espresso tamper merits this depth of analysis, but then this guy is Stephen Porges. His career has been nothing so much as tracing a vital thread, a literal twisting, winding cord that can tie together the ideas we have been tracking in these pages. Carter studies social bonding chemistry and oxytocin. Porges studies the neural structure of social bonding, especially the vagus nerve. Think of it as Carter knowing the software and Porges specializing in the hardware. But this nerve is also where all the topics we’ve been thinking about seem to converge, in signals along the vagus and the central nervous system, in which it is a key player. Remember that when we considered the sweep of evolution and its intention for our well-being, it brought us ultimately to social bonding; the whole business—the brain, exercise, eating, minding, and sleeping—traced in the end to our need to deal with one another, to empathy and altruism. More than any of our other signature traits, these two require the most brain power and allow us to be who we are, the most social of social animals. These are the capstones. And when we parse that out, especially when considering the evolutionary context—our deep history as pieces of meat for predators—then all of this must have something to do with stress, fear, terror, and dealing with these matters in order to sur
vive.
Elizabeth Marshall Thomas, the writer who spent her formative years with African hunter-gatherers, writes a great deal about lions in her account of the San people of the Kalahari. The San people she knew did indeed face lions as predators, as all people have for almost all of time. Yet these people seemed to have a finely wrought and intricate relationship with lions, the animals that owned the night. “Among the people we knew, only lions generated profound respect,” she wrote.
“Respect.” Not “terror,” but “respect.”
Thomas witnessed a number of confrontations between lions and the San people and describes nowhere any reaction that looks the slightest bit like panic. No one ran from lions. No one froze in fear. No one, certainly, engaged in fight. So here it is, the fundamental, raw, tooth-and-bone confrontation with the barest facts of biology, and yet there’s no evidence whatsoever of resorting to the basic biological mechanisms for terror: fight, flight, or freeze. Instead, there is respect.
But there is more in the specifics of what is really going on. Far from fleeing a lion, San people had a “protocol” (Thomas’s word)—and it involved walking. Walking calmly, unhurriedly, and not directly, as fleeing prey might, but obliquely at an angle, away from the lion. At the same time, they spoke to the lion, in well-modulated tones of respect, addressing it as “old lion.”
Richard Manning has had a direct and similar personal experience with a grizzly bear in the wild and observed exactly the same protocol, accepted by bear biologists as the way to deal with these big predators. The protocol is ancient and endures and has much to say about meeting not just predators but the challenges of modern life. Porges thinks he can trace the development of that protocol in the body’s most ancient and tortuous nerve, the vagus nerve—it gets its very name from the same word as “vagabond,” a wanderer, a traveler, a time traveler.
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