Why did humans start making music? Some say it was a sort of mating call. Others suggest we used rhythm and loud noise to scare off predators. But a new study found songs from all over the world share many common features, like rhythm and pitch, lending some validity to another theory: music developed as a way to bring communities together.

"It may be a little bit of a no-brainer, but for a long time, I think, people had this idea of music being an individual expression," says Pat Savage, a PhD student from the Tokyo University of the Arts and the lead author of the new study. "But throughout the world, it’s almost always in groups and seems to almost always be about bonding these groups together."

Using the Garland Encyclopedia of World Music, an online repository for global music research, Savage listened to and scrutinized 304 very different songs from nine regions: Africa, South America, east Asia, south Asia, southeast Asia, the Middle East, Europe, and Oceania. He classified each song based on 32 musical features, including the number of beats, the kind of singing voice, and even the sex of the performers. This had to be done manually. "Technology has a long way to go," Savage says. "It’s not anywhere near as good as human ear."

Savage identified 18 features that are predominant throughout the world’s songs. These include discrete pitches (where each note is expressed individually, rather than sliding from one note to another) and equally timed beats.

Listen to an example: a Palestinian line dance called "Sahjih" contains all of these features. And on the other end of the spectrum, here’s a song from Papua New Guinea that is an extreme outlier because it has no discrete pitch or timed beat.

Male performers tend to dominate throughout the world, the research showed, reflecting the restrictions on women in many cultures. "We don’t think this is biological or wired into our genes that women can’t make music," Savage explains. "Certainly women are great at making music when they’re allowed to. It’s a cultural thing."

Savage also found 10 features that appear together. "These individual features themselves are not always there, but when they are, they appear in tandem," he says. For example, dance doesn’t appear frequently, but when it does, it’s almost always accompanied by simple repetitive phrases, percussion, a regular beat, and group performance.

"The results show that the most common features seen in music around the world relate to things that allow people to coordinate their actions," says co-author Thomas Currie, of the University of Exeter, "and suggest that the main function of music is to bring people together and bond social groups. It can be a kind of social glue."