The world’s greatest yodelers aren’t found in Alpine villages but in Latin American rainforests, where monkeys perform vocal gymnastics that would leave even the most accomplished human singers breathless, according to groundbreaking new research.
Scientists have discovered that certain New World monkeys can yodel across a frequency range more than five times larger than what humans can achieve, with some “ultra-yodels” spanning over three musical octaves in a single call. This remarkable ability stems from special anatomical structures that humans lost during evolution to enable more stable speech.
“These results show how monkeys take advantage of an evolved feature in their larynx – the vocal membrane – which allows for a wider range of calls to be produced, including these ultra-yodels,” explains Dr. Jacob Dunn, Associate Professor in Evolutionary Biology at Anglia Ruskin University in Cambridge, England, who co-led the research.
The study, published in the journal Philosophical Transactions of the Royal Society B, combined field recordings from Bolivian rainforests with laboratory experiments and computer simulations to understand how these extraordinary sounds are produced.
Researchers recorded the calls of several monkey species, including the black and gold howler monkey, tufted capuchin, black-capped squirrel monkey, and Peruvian spider monkey. They discovered that the monkeys produce their distinctive voice breaks by suddenly switching sound production from their vocal folds to thin ribbon-like structures called vocal membranes that sit above the vocal folds in their larynx.
Unlike human yodeling, which typically spans one octave or less, some of the monkey calls recorded showed frequency jumps up to twelve times higher – equivalent to jumping three and a half octaves in a single vocalization. For comparison, that would be like a human singer instantly leaping from a low bass note to well beyond the highest note of a soprano, something physically impossible for human vocal anatomy.
“This is a fascinating example of how nature provides the means of enriching animal vocalisation, despite their lack of language,” said Dr. Christian T. Herbst of the University of Vienna, the study’s lead author. “The production of these intricate vocal patterns is mostly enabled by the way the animals’ larynx is anatomically shaped, and does not require complex neural control generated by the brain.”
To prove their theories about how these sounds are produced, the scientists conducted experiments with excised monkey larynges and created computer simulations that successfully reproduced the unique vocal patterns.
The research revealed that New World monkeys, whose range stretches from Mexico to Argentina, have evolved the largest vocal membranes of all primates. These thin extensions of tissue likely play a crucial role in enriching their vocal repertoire, potentially helping them communicate complex information in their social groups.
Professor Tecumseh Fitch, an expert in human vocal evolution from the University of Vienna and co-author of the study, explained: “Our study shows that vocal membranes extend the monkey’s pitch range, but also destabilize its voice. They may have been lost during human evolution to promote pitch stability in singing and speech.”
This evolutionary trade-off suggests that while humans gained more stable and controlled vocalization for speech, we lost the ability to produce the extreme vocal gymnastics that our primate relatives retained.
The findings provide valuable insights into primate communication and the evolution of human speech. They also suggest that the complex nature of monkey calls might be less about brain complexity and more about clever anatomical adaptations.
“This might be particularly important in primates, which have complex social lives and need to communicate in a variety of different ways,” notes Dr. Dunn. “It’s highly likely this has evolved to enrich the animals’ call repertoire, and is potentially used for attention-grabbing changes, call diversification, or identifying themselves.”
So next time you hear an impressive Alpine yodeler, remember that deep in the rainforests of Latin America, monkeys are performing vocal feats that make human yodeling look like child’s play – all thanks to a tiny piece of tissue that humans lost on our evolutionary journey toward speech.
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