Elevated vagus nerve activity, then, orients the individual to a life of greater warmth and social connection. Nancy Eisenberg has found that seven-and eight-year-olds with a higher resting vagal tone are more helpful in class, more sympathetic to those in need, more pro-social toward their friends, and experience more positive emotions. College students with higher resting vagal tone are better able to cope with the stresses of college—exam periods, career choices, the vicissitudes of romantic life. Following the loss of a married partner, people with high resting vagal tone recovered more quickly from the depressive symptoms that often accompany bereavement. And on the other end of the continuum, people experiencing severe depression, and its accompanying impoverishment of social connection, have been shown to have low resting vagal tone.
If William James had been a psychophysiologist with a high-tech lab, and had been able to study the vagus nerve, I suspect he would have brought Walt Whitman in—an inspiration to James and a source of his writings on the optimistic and embracing spirit. James observed that Whitman was known by all to be uniformly kind, generous, and upbeat. Had James recruited Whitman as a participant, and hooked him up to electrodes near the heart and to the respiration band around his girth to derive an assessment of Whitman’s baseline vagal tone, I bet he would have found his vagal tone to be stratospherically high, and to soar at each thought of the beauty of our species or the wonders of leaves of grass.
THE SPREAD OF SELFLESS GENES
The great shift in early hominid social organization had to do with the arrival of hypervulnerable, big-brained offspring. The success of getting genes to the next generation hinged in unprecedented ways on getting dependent offspring to the age of viability and reproduction—a hair-raisingly long thirteen or fourteen years. Our vulnerable offspring shifted the reproductive dynamics of females and males toward a pattern of serial monogamy. Our vulnerable offspring’s need for care got fathers into the act—hominid fathers provide more care for offspring than almost all other primates. The vulnerability of our offspring, Sarah Blaffer Hrdy writes in
The profound vulnerability of our big-brained offspring wired into us an instinct to care. It created in us a biologically based capacity for sympathy. It produced a vagus nerve, loaded up with oxytocin receptors, the provenance of feelings of devotion, sacrifice, and trust. It yielded a rich set of signals—empathic sighs, oblique eyebrows, and soothing touch, which trigger vagus nerve response and oxytocin and opioid release in the recipient, giving rise to oceanic feelings of connection. It produced specific cells underneath the surface of the skin that fire in response to the slow, soothing touch of compassion. The selection pressure to take care produced the indescribably beautiful qualities of the offspring themselves, designed, as many have argued, to reset the parents’ nervous systems toward more caretaking settings. When parents look at pictures of their new babies, the orbitofrontal cortex lights up, as does a region called the periaqueductal gray, a bundle of neurons known to coordinate the patterned actions of grooming in primates. So great is the evocative power of the baby that baby-faced cues in adults—big forehead, big eyes, small chin—trigger trust and liking in other adults, and short-circuit the tendency to punish (if you’re on trial, you’re well served by increasing the size of your forehead and eyes).
But evolution did not stop there. So critical was caretaking to the survival of our species that it was selected for in other ways, guaranteeing that the capacity to be kind would be woven into the genetic fabric of this new hominid. A first is through sexual selection, the processes, initially described by Darwin, according to which certain individuals prevail in competitions with their own sex to gain access to mates, thereby gaining reproductive opportunities and increasing the likelihood of passing on their genes to the next generation. What sorts of people prevail in the meat markets, singles bars, speed dating and online dating services, and more run-of-the-mill matchmaking of modern life? Full-lipped women or men with six-pack abs? Actually, Geoffrey Miller has argued, the victory goes to the kind.
Kindness is the most important quality women and men seek in romantic partners.