On quiet nights in the forests of eastern Paraguay, songs drift through the air. But none of them are lullabies to comfort crying babies and no one gathers to dance.

That unusual behavior has upended one of the most persistent ideas in anthropology: that music—especially lullabies and dancing—is universal among humans.

After 43 years of immersive research with the Northern Aché, an Indigenous group in eastern Paraguay, anthropologists Manvir Singh and Kim Hill report something startling in Current Biology: the Northern Aché do not dance, and they do not sing to their babies.

The View from the Forest

Kim Hill, a professor at Arizona State University and co-author of the study, first began working with the Aché in 1977. Over 122 months—more than 10 years—he lived among them, sharing meals, trekking with forest bands, and even attending births and funerals. He kept watch in the early hours and sat beside evening campfires. Hill speaks fluent Aché and formed bonds with families over generations.

In all that time, he never anyone singing a lullaby to a baby.

Northern Aché adults do sing—but always when they’re alone. Men tend to chant short, wordless melodies followed by bursts of improvised lyrics, often about hunting or social conflict. Women sing more rarely, often about dead loved ones, their songs weaving between melody and ritual weeping. Children sometimes mimic these songs, but always in solitary play.

Despite countless hours of observation, Hill never saw group music-making, coordinated dancing, or singing directed at infants. And it wasn’t due to lack of opportunity. Hill and his colleagues spent thousands of hours tracking women’s and infants’ activities. Parents soothed babies through speech, smiles, and laughter—but never with song.

Rethinking What’s “Universal”

For decades, researchers believed dance and lullabies were human universals—behaviors found in every society, deeply embedded in our biology. That belief has shaped theories about the origins of music, suggesting it evolved to foster mother-infant bonding or strengthen group cohesion through dance.

But the Aché offer a counternarrative.

“This doesn’t refute the possibility that humans have genetically evolved adaptations for dancing and responding to lullabies,” Singh said. “It does mean, however, that cultural transmission matters much more for maintaining those behaviors than many researchers, including myself, have suspected.”

The absence of these musical behaviors doesn’t appear to be rooted in a lack of capacity or utility. “Aché parents still calm fussy infants,” Singh noted. “They use playful speech, funny faces, smiling and giggling. Given that lullabies have been shown to soothe infants, Aché parents would presumably find them useful.”

OK so… why?

The researchers believe dance and infant-directed song were once part of Aché culture—but were lost. The reasons lie in a history of hardship. The Aché suffered drastic population declines due to disease and displacement in the 20th century. These bottlenecks, combined with relocation to reservations and missionary influence, may have stripped away layers of cultural complexity.

The same forces, Singh and Hill suggest, erased other practices—like fire-making, shamanism, and puberty ceremonies. Today, Northern Aché no longer know how to start fires; they preserve embers instead. Meanwhile, Southern Aché groups—more acculturated—still exhibit dancing and group music-making.

It’s a pattern with precedent. Similar cultural losses have been documented in Tasmania and among other Indigenous South American groups. Populations reduced by disease or violence often lose specialized knowledge, rituals, and arts.

Genetic studies back this up: the Northern Aché show signs of repeated genetic bottlenecks, which likely mirror the erosion of cultural traits over generations.

The findings force a shift in how we think about what’s “natural.” Some human behaviors, like smiling, emerge spontaneously even in isolation. Others, like fire-making—or singing lullabies—require learning and transmission.

That doesn’t mean we’re not biologically prepared for these behaviors—only that they don’t emerge automatically. They depend on community, tradition, and the passing of knowledge from one generation to the next.

And when that chain is broken, the song can fall silent.