Ben Monkaba’s smile stretches from one red sideburn to the other. When I recently spoke to him over Skype, his grin never left his face. He told me about the ups and downs of his childhood and how much he loves performing—as a drummer and vocalist, and also as a professional clown. He was once invited onstage to sing with the Beach Boys at a fair in Massachusetts. “That was a moment I’ll never forget,” he says. “They were really friendly.”
Monkaba, now 33, has been exceptionally sociable all his life. At elementary school, he was known as “the Mayor” for the way he would enthusiastically greet anyone and everyone walking past him, his mother, Terry, tells me. And at social gatherings, he would compulsively compliment everyone on their appearance. “It would be, ‘What a lovely yellow dress you have on.’ Or ‘Is that a new hairdo?’ and ‘I love your nail polish,’” Terry says. Her son was so charming that her friends used to suggest that he work as an emcee for charity events.
Monkaba’s “hyper-sociality” is just one sign of his rare genetic condition. Williams syndrome affects about one person in 10,000, and some who have it are so impulsively affectionate, and so devoid of our typical social inhibitions, that they will hug complete strangers on the street, says Jocelyn Krebs, the president of the Williams Syndrome Association (WSA) and the mother of a boy with the condition. “There is a desperate need for human contact, and they have zero social anxiety about the approach and opening [of a conversation],” she says.
Besides their gregariousness, people with Williams syndrome have a distinctive physical appearance, with delicate features such as a small, upturned nose and a pointed chin. And the condition often comes with a constellation of challenges and health risks, including learning difficulties, poor movement coordination, digestive issues, and life-threatening cardiovascular illness.
Ben has already undergone multiple surgeries as a result of his Williams syndrome, though he tends to downplay his discomfort. “He’s been through so much,” says Terry, who is also a spokesperson for the WSA. “But he just doesn’t go there, you know? His spirit is all about the good stuff.”
Scientists have had a tough time explaining all the diverse symptoms and characteristics associated with Williams syndrome. Recently, however, great strides have been made in understanding the condition’s origins, including the reasons that people with Williams syndrome are so sociable. In an unexpected twist, some evolutionary biologists believe this research could even shed light on the mysterious roots of human altruism.
Cardiologists first identified the basic attributes of Williams syndrome in the 1960s, but it was only in the 1990s that scientists managed to pinpoint the condition’s genetic basis. People with Williams syndrome lack 26 to 28 neighboring genes on the seventh human chromosome. This region includes various genes with diverse functions, from regulating immune function to controlling organ growth and development. One gene codes for a highly flexible protein that is essential for many bodily tissues. A deficit in this protein thickens the artery walls with muscle, leading to lifelong cardiovascular problems.
The loss of another gene, BAZ1B, impairs the migration and survival of what are known as “neural-crest cells” across the body. In an embryo’s early development, these cells usually gather at the head and then move across the body, where they form the basis for many tissues—including the bones and cartilage in the face, the teeth, and the eyes, as well as the heart and the digestive system. A disruption of this process leads to Williams syndrome’s markedly different facial features.
Neural-crest cells also form the adrenal glands, which shape our hormonal responses to stressful events. Some scientists have argued that the reduced migration of neural-crest cells could contribute to reduced fear and aggression—potentially leading to increased social behavior. That would certainly fit with the experiences of many people with Williams syndrome, who find it harder than the average child to comprehend “stranger danger.” “When I was younger, it was hard, because I wanted to go up to every single person and say hi, and I wanted them to be my friend,” Maegen Miller, a 30-year-old woman with Williams syndrome, told me. This theory tallies with various measures of social behavior, which show that people with Williams syndrome tend to be less sensitive to others’ negative emotions and signs of hostility, so that literally everyone can seem approachable.
Ultimately, though, such characteristics probably arise through many different mechanisms. Most people with Williams syndrome are also missing a gene called GTF2I, which contributes to the production of myelin, the fatty sheaths that normally surround our brains’ neural connections. The loss of myelin likely impairs the transmission of electrical signals across the brain, which could help explain some of the cognitive difficulties and the lack of motor coordination associated with the condition.
Researchers at MIT have recently shown that, in addition to the motor problems, the deletion of GTF2I produced more social behavior in laboratory mice. The animals were more likely to approach a second, previously unknown mouse, for instance. Exactly why the myelin loss could influence social behavior is still a mystery, but one of the scientists, Boaz Barak, believes that it might disrupt communication between the amygdala, which processes emotions such as fear, and the frontal cortex, which is important for decision making. This could prevent the typical feelings of suspicion or distrust from inhibiting social interactions.
Such results are of great interest in medicine. Finding new ways to mitigate the effects of the protein deficiency that thickens artery walls, for instance, could radically reduce Williams syndrome’s most serious cardiovascular risks. Still, scientists such as Barak are keen to tread carefully in treating the cognitive and behavioral differences. Barak’s experiments on mice demonstrated that you can reverse some of the brain changes associated with Williams syndrome using a standard antihistamine drug. But the drug also reduced hyper-sociality. Many of the families of people with Williams syndrome would consider that a serious loss.
“There’s this misconception that anyone different from neurotypical is somehow less,” says Cyndra Cole, the mother of 11-year-old Eden. “I cannot tell you how much Eden has taught me that she is certainly not less. In fact, in many ways, I think that she’s more.”
The potential implications do not end with medicine. Some evolutionary biologists hope that these findings could offer some insights into the origins of human cooperation more generally. Other apes, such as chimps, tend to live together in much smaller numbers than humans—and although they can cooperate on activities such as hunts, in-group violence is still far more common than the aggression we see in human societies. Although these differences are widely documented, the evolutionary processes that led to humans’ friendlier and more collaborative disposition have remained a mystery.
According to one prominent hypothesis, endorsed by researchers such as Richard Wrangham of Harvard University, humans “self-domesticated” by eliminating the most aggressive members from the gene pool—either through capital punishment or through sexual selection, in which people started to opt for less violent individuals to be the parents of their children. Over time, the species as a whole became less hostile and more cooperative. This profound change, the theory goes, allowed for agriculture, art, and other forms of culture to flourish.
The idea is supported by the fact that modern humans share some surprising characteristics with many domesticated animals. The taming of animals such as wolves or foxes, for instance, leads to physical characteristics such as smaller bodies, shorter noses, and smaller teeth. That’s exactly what we see in human faces, which are generally less boorish than those of our evolutionary relatives, such as the Neanderthals. Even so, it has been far from clear why selecting for a certain kind of behavior could produce such diverse changes in appearance.
Some clues may lie in those 20-odd genes on chromosome 7. Given the recent research on BAZ1B, for instance, it’s possible that the process of domestication alters the genes controlling neural-crest cells. That could reduce aggression and promote cooperation by reducing the adrenal glands, while also resulting in the more delicate facial features that are common to humans and domesticated animals.
If so, you would expect to see signs that these genes have changed in recent evolutionary history. And that’s exactly what Cedric Boeckx at the University of Barcelona has recently been trying to test. The experiments are a collaboration with Giuseppe Testa and his team at the University of Milan and the European Institute of Oncology. Testa spearheaded the first in vitro models of Williams syndrome with stem cells derived from the skin. Using these tissue samples, the group confirmed the hypothesis that lower levels of BAZ1B resulted in reduced neural-crest migration. The team also examined tissues from people who had duplicated copies of BAZ1B—which, as expected, produced the opposite effect, resulting in greater neural-crest migration.
The next step was to examine the role of neural-crest cells in evolution. The team identified which genes are regulated by BAZ1B, and which might therefore be involved in neural-crest migration. By comparing the modern human genomes with those of our closest relatives, the Neanderthals and the Denisovans, they found signs that BAZ1B and its targets had indeed undergone significant selection in the recent history of Homo sapiens. This included a sweep of specific mutations appearing far more frequently within these areas—just the kind of changes you would expect if certain traits are being preferentially chosen within a population.
Boeckx and Testa recently published their paper as an online preprint that has not yet been peer reviewed. So far, it’s only the first glimmer of evidence that self-domestication altered behavior and appearance through changes to our neural-crest cells. But the research might just be the start. One of the other genes implicated in Williams syndrome, GTF2I, which may also alter neural-crest cell migration and hyper-sociality, has similarly experienced significant changes during recent human evolution, and appears to be altered in other domesticated animals. Further investigations of the condition might provide much more evidence for the self-domestication hypothesis and its consequences for human nature.
It is a profound idea that, at some point in our history, humans began to take their evolution into their own hands, turning us into the uniquely cooperative animals we are today. Williams syndrome may affect just one in thousands of people, but by inspiring this research, its traits might help us understand the social instincts in all of us.
We want to hear what you think about this article. Submit a letter to the editor or write to firstname.lastname@example.org.