Growing Young

by Marta Zaraska

  Which, by the way, is not a particularly good thing. Research shows that people with an AA variant of an oxytocin receptor gene called rs53576 are less empathic, have more trouble reading feelings from other people’s faces, are judged as less friendly by others, and, if they are mothers, parent their kids with less sensitivity in times of parental conflict. People with the GG genotype, on the flip side, are generally more socially inclined and more attuned to the emotions of others. The GG genotype is the one you are more likely to have, since only 15 percent of people are type AA.

  Scientists say that existence of these different genotypes makes sense from the evolutionary perspective. For our ancestors, safety was in numbers, so evolution favoured those who craved the bond with others, and hence may the GG genotype have survived. On the other hand, the group also needed people who were less upset by being alone, those who might venture far away and explore the environment, such as the carriers of the AA genotype.

  Yet your oxytocin-related genes, no matter whether you are an AA type or GG type, are not the end of the story. They don’t doom you to being more or less social nor do they determine how you will interact with others. Having the AA genotype doesn’t mean you will certainly be a loner, and as a result, live less long. Your environment is important, too, whether it’s your social network—or what gets sprayed up your nose.

  The Elixir of Youth

  On one late afternoon in 2007, several couples entered the unassuming steel-and-concrete buildings of the University of Zurich, and headed for the psychology lab—a scene that would repeat itself many times over the following six months. The men and women, in their twenties, thirties, and forties, were to take part in an experiment on the effects of oxytocin on relationships. First, everyone was asked to chew on a synthetic swab, something that looked like a third of a cigarette, which soaked up saliva. This way the levels of cortisol, the indicator of stress, could be measured. The couples were then given a list of potentially conflict-inducing topics (money, work, parenting, etc.) and asked to pick the two that they considered the most burning in their own relationship. Afterward, everyone was handed a nasal spray that resembled my OxyLuv, and told to puff five times in each nostril. Some people received oxytocin, and some unknowingly got placebo. When the drugs kicked in, it was time to fight. The couples were enclosed alone in a room with just a video camera recording and told to “discuss” the pre-chosen conflict issues. The squabbles began.

  After the “conflict discussion,” as the scientists euphemistically called it, saliva samples were taken repeatedly to measure the changing levels of cortisol. By dinnertime the experiment was over and the couples went home. For the researchers, though, the work was merely beginning. Months down the road, when all the behaviours recorded on video had been analyzed and the cortisol levels charted, the results were announced: the couples who took oxytocin not only had less cortisol in their saliva, they were also less nasty when fighting. Even though the oxytocin-drugged couples threw contemptuous remarks and rolled their eyes at each other just like everyone else did, they made up for such negative behaviours with more eye contact, smiles, and talking openly about feelings. That was crucial: a high ratio of positive to negative interactions is a great predictor of marital stability.

  There are plenty of other studies that show that spraying oxytocin into the nose affects our social skills. It makes us better at reading facial expressions of emotions, such as telling whether someone is sad, tired, or just bored. It makes us more trusting. It can even make husbands stand further away from pretty women, as I’ve mentioned. When men in committed relationships were asked to find a spot at the “most comfortable” distance from a very attractive female experimenter, those who had previously received intranasal sprays of oxytocin opted for a distance of twenty-eight inches (71 cm). Those who only had the placebo preferred to stand considerably closer to the woman—twenty-two inches (56 cm) away, suggesting that without extra oxytocin, they behaved more like montane voles than the prairie ones, with faithfulness less on their minds.

  Oxytocin not only makes us loyal, less quarrelsome, and more empathic, studies also show that it can directly affect our physical health, which would help explain the many links between sociality and longevity. The underlying reason here is this: nature is lazy. It reuses stuff. Just like your favourite mug may be for drinking coffee one day and then for storing pencils another, molecules such as oxytocin have been repeatedly repurposed for various functions over our evolutionary history. First, it was simply regulating water balance to prevent dehydration. Then it was immunity and metabolism. And then other functions were added, such as activating the milk let-down reflex during breastfeeding. From there nature repurposed oxytocin and related hormones for regulating our social behaviours. But it’s all still connected. Changes to the system influence all the uses—just like changes to neural crest cells could both affect friendliness of foxes and create spots on their foreheads. If oxytocin levels surge in your body—say, because a scientist sprayed the neuropeptide into your nostrils—you may suddenly feel more lovey-dovey to the people around you, and your health may be affected, too.

  One of the key roles here is played by the amygdala—the fear centre that was damaged in the reckless SM, whom we met in Chapter 2. The amygdala reacts strongly to oxytocin, which can moderate the activation of the amygdala in response to stressful situations, calming us down. This means that SM, with her damaged amygdala, would likely not benefit much from oxytocin sprays—at least not where fear was concerned. Oxytocin also reduces stress by acting directly on the HPA axis. The very neurons in the brain that kick off the HPA response carry receptors for oxytocin, and if the molecule binds to the receptor, it puts brakes on the activation of the HPA axis and the cortisol release. You feel less stressed—and stay healthy.

  Such receptors for oxytocin are found not only inside our brains but all over our bodies. We have them in our bones, our hearts, even in our guts. It’s hardly surprising, then, that plenty of studies have found links between levels of oxytocin and health. There is evidence that oxytocin has anti-inflammatory properties, that it promotes formation of new neurons in adult brains, that it reduces pain, and that it helps bone growth, potentially preventing osteoporosis. Oxytocin’s effects are so powerful that some researchers have even dubbed it the “elixir of youth.” If Ponce de León were still alive, he might consider his search over.

  A direct proof of oxytocin’s role in both sociality and health comes from voles (yes, those cute rodents again)—a proof that would be hard to obtain in humans for ethical reasons. In one study conducted at Florida State University, female voles were kept in isolation for four weeks. After the animals were released back into their group, the scientists noticed that not only were they more aggressive, their hearts were in far worse shape, too. Yet these effects could be reversed with simple injections of oxytocin.

  Oxytocin may be the most studied neuropeptide linking our social lives with our health, yet it’s certainly not the only one. There is also serotonin—the very hormone which has been discovered to be particularly abundant in the brains of tame Siberian foxes, and which has also contributed to the evolution of our domesticated species.

  Unfaithful Mice and the Benefits of Massage

  In the summer of 2014, the capital of Madagascar, Antananarivo, was hit by a swarm of locusts, consisting of billions of insects, flying in unison like a dark cloud of smoke rising above the houses. Similar plagues have been seen in Egypt, Israel, the American Midwest, and Australia.

  At their most typical, locusts are not social creatures. They are loners. What makes them change into collective animals that may share close space with even ten billion others is the hormone serotonin.

  Serotonin, also known as the “feel-good hormone,” can not only make locusts more sociable—it can make humans more friendly, too. People who have higher levels of serotonin circulating in their systems are more cordial and agreeable. Even your succ
ess in speed dating may be affected by serotonin. When scientists followed over a hundred single Asian-American men who went on speed dates where each of the encounters lasted a mere three minutes, they discovered that those who had one particular variation of serotonin receptor genes had more luck—they were more likely to score a second date than those with another version of the gene.

  While abundant serotonin causes us to be friendly, social isolation makes the levels of the neurotransmitter plummet, which in turn can prompt aggressive behaviours—an effect that has even been observed in lobsters. Serotonin has also been linked to blood pressure, Alzheimer’s disease, pain perception, vascular tone, temperature regulation, and vomiting. In mice, serotonin can help regenerate the liver. In humans, low serotonin is associated with metabolic syndrome, a risk factor for heart disease. It has even been directly connected to longevity—at least in some animals, including mice and worms. One study of Japanese centenarians suggests there may be a link in humans, too. When researchers compared the serotonin transporter genes of those who’ve made it to at least a hundred to those of a younger control group, they discovered significant differences in how frequently one type of allele was present among the oldest people.

  Just like with oxytocin, one way in which serotonin may be affecting our health is through its action on the HPA axis and on the production of the stress hormone cortisol, with more serotonin meaning, in general, less cortisol. In addition, serotonin can interact with oxytocin, each regulating the other’s release, basically creating a feedback loop.

  Another social neuropeptide, vasopressin, also interacts with oxytocin and orchestrates both our social lives and our health. Vasopressin is important for wound healing, kidney function, cardiovascular disease, and other functions. Unlike oxytocin, though, vasopressin seems more relevant to men. Also unlike oxytocin, it appears that more vasopressin circulating in the body is not necessarily better, since it can elevate blood pressure and can make men more aggressive. The likely reason for the hostile attitudes spurred by vasopressin is that the hormone is very much about guarding your loved ones from outside dangers. It can make rat mothers fiercely protective of their babies, and make prairie vole males possessive of their mates. It can also make some animals ditch their loose sexual habits altogether and become monogamous.

  If you took cutesy pictures on greeting cards seriously, you might conclude that mice make particularly devout partners. From Valentine’s Day to birthday cards, drawings of mice in love abound in stationery stores across the world. Yet from a biological perspective, those images are off the mark: in many species of mice, including your typical house mouse, both males and females swap partners left and right.

  But if you would like to turn a mouse monogamous, Romeo-and-Juliet style, there is a way to do it, as long as you know how to insert genes from one species to another. Back in the late 1990s, Larry Young and his colleagues at the Atlanta lab took a vasopressin receptor gene out of prairie voles, those till-death-do-us-part-faithful rodents, and popped it into the genomes of male mice, creating a new type of transgenic animal. The new mice had a similar pattern of vasopressin receptors in their brains to prairie voles, and behaved in quite the prairie vole way as well: they were now more into huddling and grooming their female partners Hallmark-style.

  In a similar fashion, by manipulating just one single vasopressin-related gene, Young and his colleagues managed to make meadow voles, which are as promiscuous as montane voles, more devoted to monogamy. And although you can’t exactly have your spouse injected with prairie vole monogamy genes, studies do show that vasopressin is also related to marriage quality in humans. A study of Swedish twins revealed that in men, polymorphisms of one vasopressin gene in particular, called AVPR1A, can affect how well spouses get on together—how often they kiss, how much they enjoy common hobbies, and how often thoughts about divorce cross their minds. For those who might be wondering: yes, you can order a genetic test for your future spouse to check his AVPR1A. All you need is a small vial of his blood, which you then send to a lab (for instance one in Temple City, California, provides such services). Whether doing so would be a good idea is another question—it might redefine the word “bridezilla.”

  An easier option for changing levels of vasopressin in human bodies to affect both health and behaviour involves small bottles with spray nozzles. In experiments, squirting vasopressin up people’s noses has been shown to improve sleep and memory and to make women more conciliatory and men better at cooperation (the two genders tend to react differently to vasopressin—and sometimes to oxytocin, too). And just like the OxyLuv that I tested, you can order vasopressin nasal sprays on the internet. A bottle of Vaso-Pro sold on one website out of Hong Kong will set you back $69.99.

  It may be quite tempting to order a container of OxyLuv and Vaso-Pro off the net and start spraying day in, day out. Please don’t do that. Although such silver bullet solutions may be quite appealing, there are plenty of reasons why you shouldn’t try to improve your longevity prospects by drugging yourself—or others—with non–FDA approved products (such sprays are for now only approved for use in lab experiments). We know extremely little about the long-term effects of oxytocin and vasopressin sprays, or their side effects. It’s simply too risky. Luckily, though, you can boost the levels of your social hormones by using far safer measures. Like hugging.

  Good animal moms have oxytocin-loaded kids. When mama rats engage in a lot of skin-to-skin contact with their babies, the little ones have increased concentrations of oxytocin in their blood. Humans are not much different: plenty of studies show that kissing, embracing, and even massaging raises oxytocin levels. What’s more, the more oxytocin circulates in your blood, the more of it will be produced in the bodies of your children. Mothers and fathers who have high oxytocin are more responsive, more sensitive, and warmer toward their kids—hugging and kissing them more often, for example. So if you want your children to have higher levels of oxytocin, don’t just hug them—hug your partner in parenting, too.

  Back in antiquity, the Greek father of Western medicine, Hippocrates, claimed that “rubbing” was an important skill for any good physician to acquire. Contemporary research confirms that massages can boost oxytocin, leading to better health and, presumably, to longer lives. Same goes for other social hormones. Massage therapy can boost serotonin by 28 percent and dopamine by 31 percent. A massage with “a happy ending” works well, too—orgasms are quite good at raising oxytocin levels in the blood.

  To get even more of the health-boosting and life-prolonging benefits of social hormones, don’t just hug and massage your loved ones—do so while gazing deeply into their eyes. In a rather unsurprising finding, the more a mother looks at her baby’s face, the more oxytocin gets pumped into her body. More remarkable was an experiment published in 2015 in the journal Science, which revealed that exchanging long gazes with your family pooch also boosts oxytocin levels—both in the dog and in the owner.

  Simply spending time with others works well on your social hormones. When little mice are allowed to interact with other little mice in their nest, they grow up to have more oxytocin receptors in specific areas of their brains. Although, as far as I know, it hasn’t been yet studied whether more playtime boosts oxytocin in human kids, there is evidence that after hanging out with their friends, adults have more oxytocin in their blood.

  As for serotonin, you may have heard that stuffing yourself with foods abundant in the amino acid tryptophan, such as meat, will give you a serotonin boost, elevate your mood, and prolong your life. In reality, the meat-tryptophan-longevity link is a myth. Although it is correct that in experiments, giving people tryptophan supplements prompts them to produce more serotonin, and in turn makes them less irritable and quarrelsome, because of the way tryptophan is transported into the brain, foods containing tryptophan don’t increase brain serotonin.

  Luckily, you don’t need to worry about your tryptophan intake—getting yo
ur serotonin from friendly back massages is completely safe and far more natural than taking pills. Our hominin ancestors didn’t have access to either OxyLuv or tryptophan supplements—reciprocal grooming worked well enough for them.

  * * *

  The physiological connection between how friendly we are and how long and healthily we live makes perfect sense. After all, we have evolved this way. We have self-domesticated ourselves to be less aggressive and more trusting, more open toward others. As a result, our bodies have changed. Selection for higher levels of social hormones such as serotonin, dopamine, and oxytocin has left us with smaller jaws, flatter faces, and white eye scleras—and made our pink lips a simple reminder of how important social hormones were in the evolution of our species, and how much they can impact our bodies.

  Today, social hormones are still the link between the quality of our friendships and family life on one hand, and our health and longevity on the other. They can explain why good marriage may equal good arteries and why having your best friend over reduces stress.

  But as oxytocin, serotonin, or vasopressin go, we aren’t all wired the same way. Some of us may carry the AA allele of oxytocin receptor gene rs53576 and find it harder to get socially involved. Others may have the version of a vasopressin gene that makes working on a marriage an uphill struggle. But if that’s the case for you, you certainly aren’t doomed. You can still get more of the social hormones and their benefits by simply hanging out with your friends or hugging your family.