For more writing from Discover blogger Carl Zimmer, see his new ebook, Brain Cuttings: Fifteen Journeys Through the Mind.
When Charles Darwin listened to music, he asked himself, what is it for? Philosophers had pondered the mathematical beauty of music for thousands of years, but Darwin wondered about its connection to biology. Humans make music just as beavers build dams and peacocks show off their tail feathers, he reasoned, so music must have evolved. What drove its evolution was hard for him to divine, however. “As neither the enjoyment nor the capacity of producing musical notes are faculties of the least direct use to man in reference to his ordinary habits of life, they must be ranked among the most mysterious with which he is endowed,” Darwin wrote in 1871.
Today a number of scientists are trying to solve that mystery by looking at music right where we experience it: in the brain. They are scanning the activity that music triggers in our neurons and observing how music alters our biochemistry. But far from settling on a single answer, the researchers are in a pitched debate over music. Some argue that it evolved in our ancestors because it allowed them to have more children. Others see it as merely a fortunate accident of a complex brain.
In many ways music appears to be hardwired in us. Anthropologists have yet to discover a single human culture without its own form of music. Children don’t need any formal training to learn how to sing and dance. And music existed long before modern civilization. In 2008 archaeologists in Germany discovered the remains of a 35,000-year-old flute. Music, in other words, is universal, easily learned, and ancient. That’s what you would expect of an instinct that evolved in our distant ancestors.
Darwin himself believed that music evolved as a primordial love song. In other species, males make rhythmic grunts, screeches, and chirps to attract mates. “Musical tones and rhythm were used by the half-human progenitors of man, during the season of courtship, when animals of all kinds are excited by the strongest passions,” he proposed in The Descent of Man. And today, 139 years later, some scientists still sign on to this interpretation.
Dean Falk of the School for Advanced Research in Santa Fe, New Mexico, and Ellen Dissanayake of the University of Washington at Seattle accept the idea that a predisposition to music is hardwired, but they think Darwin misunderstood its primary function. They suggest that music evolved not only to serve love but also to soothe its aftermath. Mothers coo to their babies in a melodious singsong sometimes called motherese, a behavior that is unique to humans. Motherese is much the same in all cultures; its pitches are higher and its tempo slower than adult speech. What’s more, motherese is important for forming bonds between mother and child. Falk and Dissanayake argue that the fundamentals of music first arose because it helped form these bonds; once the elements of music were laid down, adults were able to enjoy it as well.
A third faction holds that music evolved not from any one-on-one experience but as a way to bring groups together. Robin Dunbar, a psychologist at the University of Oxford, is now running experiments to test the idea that music evolved to strengthen the emotional bonds in small groups of hominids.
Dunbar has spent much of his career studying bands of primates. One of the most important things they do to keep the peace is groom one another. Grooming triggers the primate brain’s hypothalamus to release endorphins, neurotransmitters that ease pain and promote a feeling of well-being. Our early ancestors may have engaged in similar behavior. As humans evolved, though, they started congregating in larger groups. By the time the average group size hit about 150, grooming was no longer practical.
Music evolved, Dunbar proposes, because it could do what grooming could no longer do. Large gatherings of people could sing and dance together, strengthening their bonds. In a few studies, researchers have found that listening to music can raise the level of endorphins in the bloodstream, just as grooming can. Recently, Dunbar and his colleagues ran experiments to learn more about music’s soothing effects. If music was important for forging social bonds, then performing music (not just listening to it) might release endorphins too.
Dunbar and his colleagues studied people who played music or danced together in church groups, samba classes, drumming circles, and the like. After the performances, the scientists made an indirect measure of the endorphin levels in the performers’ bodies, putting blood pressure cuffs on people’s arms and inflating them until the subjects complained of pain. (Since endorphins kill pain, a higher pain threshold indicates elevated levels of the compounds.) The researchers then repeated the procedure with employees of a musical instrument store who listened passively to constant background music. People who actively moved their bodies to music—dancers, drummers, and so on—had elevated pain thresholds, but no such effect showed up among those who merely listened.