When researchers at the University of Geneva slid participants into an MRI scanner and played them a series of vocalizations—from humans, chimpanzees, bonobos, and rhesus macaques—they expected to see familiar regions of the brain flare to life only for human voices.
Instead, something far more surprising happened. When people heard the calls of chimpanzees, their brains responded as if they were hearing a close cousin—because, in a sense, they were.
A new peer-reviewed study published in eLife finds that the human brain’s “temporal voice areas,” long believed to be specialized for processing human voices, also respond robustly to the vocalizations of chimpanzees, our closest evolutionary relatives.
The discovery suggests that these neural circuits are not uniquely human after all—and may trace their origins back millions of years before language emerged.
The findings reveal distinct regions within the superior temporal gyrus—an area crucial for decoding speech, music, and emotion—that activate strongly when humans hear chimpanzee calls but not when they hear bonobo or macaque vocalizations.
By disentangling acoustic properties from evolutionary proximity, the research strengthens the idea that human voice-processing circuits evolved atop ancient neural pathways shared with other primates. The findings could reshape scientific understanding of how voice recognition and, ultimately, language emerged in our species.
“Our intention was to verify whether a subregion sensitive specifically to primate vocalisations existed,” co-author and research associate at UNIGE’s Faculty of Psychology and Educational Sciences, Dr. Leonardo Ceravolo, said in a press release. “When participants heard chimpanzee vocalisations, this response was clearly distinct from that triggered by bonobos or macaques.”
For decades, neuroscientists have identified the temporal voice areas (TVA) as the brain’s specialized system for recognizing and interpreting human voices. However, whether these regions evolved uniquely for human speech—or whether they reflect deeper evolutionary roots—has remained open for debate.
To investigate this, the UNIGE research team conducted a species-categorization experiment with 23 participants. Inside the MRI scanner, subjects listened to 72 carefully selected vocalizations: 18 human utterances, 18 chimpanzee calls, 18 bonobo calls, and 18 macaque calls. The animal calls varied widely, ranging from affiliative grunts to distress or threat vocalizations.
Participants then attempted to identify which species each sound came from, but the real goal was to watch how their brains responded.
The MRI scans showed something intriguing. When participants heard chimpanzee vocalizations, the anterior superior temporal gyrus lit up in a pattern strikingly similar to its response to human voices.
However, bonobo and macaque calls did not trigger this specialized neural response.
This contrast is remarkable because bonobos are just as genetically close to humans as chimpanzees. Yet their vocalizations—higher in pitch and more bird-like—fall outside the acoustic range to which human auditory systems are tuned.
Chimpanzee calls, by comparison, share similar frequency ranges with human voices, giving them a dual similarity: evolutionary and acoustic.
To ensure that this neural activation wasn’t simply due to basic acoustic features like pitch or loudness, the researchers built three increasingly sophisticated models.
Each model controlled for different sound parameters—from fundamental frequency to high-dimensional acoustic distance—to isolate the true source of neural differences.
Across all three models, the result was consistent. Only chimpanzee calls reliably produced enhanced activity in the anterior TVA. Even after the scientists regressed out six of the most discriminant acoustic factors—such as vocalization, loudness, intensity, the bandwidth of certain frequencies, and spectral changes—the chimpanzee effect remained.
This suggests that human temporal voice areas are wired to respond to voices—or near-voices—produced by species whose vocal apparatus and acoustic signature resemble our own.
In contrast, bonobo calls, with their unusually high frequencies linked to a shorter larynx, seem acoustically “out of range” for these circuits. Macaque calls, meanwhile, are both phylogenetically and acoustically distant from humans—yet the study did detect small pockets of activation for macaque vocalizations in the mid-superior temporal sulcus when using the most detailed acoustic controls.
This suggests that certain TVA subregions may respond not only to evolutionary closeness but to very specific acoustic features found across primate species.
One of the most intriguing implications of the study is that the modern human brain may retain ancient neural mechanisms originally tuned for recognizing the calls of ancestral primates.
If chimpanzee vocalizations activate human TVA circuits more strongly than bonobo calls, despite both apes being equally related to us genetically, it may hint that the last common ancestor of humans and chimpanzees sounded more like modern chimpanzees than bonobos.
“Our data indeed show that modern human brains remain more sensitive to the acoustic characteristics of the calls of the former [chimpanzees] compared to the latter [bonobos], arguing for more conserved calls between modern chimpanzees and humans,” researchers explain.
This suggests that the neural blueprint for voice recognition, long thought to be uniquely human, may have been shaped by selective pressures predating language itself—pressures related to group living, emotional communication, and social coordination among early hominins.
For scientists studying the evolution of speech, these findings open a new line of inquiry. If the human TVA responds to chimpanzee calls due to shared acoustic features, this system may have originally evolved to process a broader range of primate communication sounds. Only later—through cultural evolution and biological adaptation—might these circuits have become specialized for human speech and language.
“Taken together, our data suggest that phylogeny-driven specific acoustic features appear to be necessary to trigger cross-species activity in the human temporal voice areas,” the researchers write.
In other words, the TVA might not be a uniquely human invention, but an elaboration built upon ancient primate foundations.
While the study is rooted in evolutionary neuroscience, its implications also extend into modern research on auditory processing, social cognition, and even early development.
The researchers note that insights from this work may help inform how voice-recognition abilities emerge early in life, including why infants—and even fetuses—are able to detect and distinguish familiar voices. While the study focuses on adults, the observed sensitivity of certain brain regions to specific acoustic features provides a framework for exploring how these mechanisms develop.
The findings could also inspire new research into how humans perceive emotional cues in nonhuman primates, how neural circuits respond to unfamiliar voice-like sounds, and how disorders of voice or speech perception might arise.
Ultimately, these findings add a fascinating new chapter to our understanding of human auditory cognition. Rather than being uniquely engineered for our own species’ voices, parts of the human brain appear to retain a deep, evolution-shaped sensitivity to the vocal patterns of our primate relatives.
Chimpanzee calls, with their human-like frequency structure, slip neatly into these receptive circuits—even if we don’t consciously recognize them as kin signals.
As neuroscience continues to map the interfaces between evolution, sound, and cognition, the humble grunt of a chimpanzee may prove to be an echo of the ancient soundscape in which our capacity for language first began to take shape.
“Our results support a critical evolutionary continuity between the structure of human and chimpanzee vocalizations, possibly reflecting one of their common ancestors, as opposed to bonobo vocalizations that underwent more recent and critical changes within the last 1-2 million years,” the researchers conclude. “In contrast, the chimpanzee vocal system may be closer to the one of the common ancestors of humans and chimpanzees, as shown by the conserved activation in the human modern brain.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com