Whether or not Neandertals could speak has been studied for more than five decades—and the question is still being researched because no definitive answer has been given. It is clear that our human relatives were capable of enormously complex cultural achievements. So how was all of that possible without the powerful communication capabilities afforded by speech?

To be sure, Neandertals were equipped with a well-known language gene. But some studies cast doubt on whether Neandertals’ anatomy was suitable for producing the sounds of speech: their larynx was shaped differently than that of modern humans. Still, it was considered likely that our cousin species could produce a wide variety of sounds. Whether those sounds rose to the level of actual speech remains controversial.

A team led by Mercedes Conde-Valverde of the University of Alcalá in Madrid has now approached the problem from a different angle: The researchers tried to find out whether Neandertals could hear complex language content. If they did have that ability, then it might stand to reason that they could have used it to good effect in listening to spoken speech. Conde-Valverde and her collaborators proceeded by examining the acoustics inside a typical Neandertal inner ear. They recently presented their results in the journal Nature Ecology & Evolution.

In chimpanzees and various other human ancestors such as Australopithecus africanus and Paranthropus robustus, the inner ear is not designed to resolve the frequency band of language particularly well. The ears of Homo heidelbergensis from the Middle Paleolithic are also not equipped for hearing languages. And what about Neandertals’ ears?

Conde-Valverde and her team made 3-D scans using computerized tomography to construct digital models of the structures of the inner ears of five Neandertals. They then compared the sound transmissions within the simulated organs with those of the ears of modern humans, older hominins and chimpanzees. This analysis enabled the Spanish researchers to deduce which pitches each ear was best attuned to. The wider the frequency band that can be detected, the more acoustic signals can be contained within it, enabling the transmission of a distinguishable signal in a short interval. The results from this work is clear: the frequency bandwidth of modern human and Neandertal ears do not differ significantly.

Neandertals could therefore hear language just as well as we do—with an acoustic sensorium that is optimally tuned to the frequencies that are particularly relevant for understanding human speech. In contrast to ears of H. heidelbergensis individuals from Spain’s Sima de los Huesos cave, which were analyzed for comparison, Neandertals could hear better at frequencies of four to five kilohertz, an acoustic capacity comparable to that of modern humans. The band of frequencies Neandertals could perceive was also as wide as that of humans.

The recent study provides only a hint of whether Neandertals were able to speak. But if they could do so, then they could hear and distinguish between a similarly wide range of sounds as humans. “Neandertals possessed a communication system that was as complex and efficient as modern human speech,” said Conde-Valverde in a recent press release.

Her team suggests that Neandertals may have used words with more consonants and significantly fewer vowels than we do today. The researchers’ analyses suggest they could hear subtle differences even between three and five kilohertz. At those ranges, they would be able to hear typical speech sounds such as high-frequency consonants, including so-called voiceless plosives, such as “t” and “k” in the English language, and so-called voiceless fricatives, such as English’s “f,” “s” and “th.”

These unvoiced consonant sounds are common in most of our species’ languages. Experts suspect they may be some of the oldest phonemes in human speech. Modern languages also transmit acoustic information in frequency ranges in which so-called formants can be heard, enabling individual vowels to be distinguished at around 2.5 kilohertz. It would be quite unusual if Neandertals could hear consonants better than vowels. By contrast, chimpanzees and many mammals tend to produce vowels in order to communicate.

Also, consonant-centered communication would explain why many earlier studies came to the conclusion that Neandertals had no linguistic talent: scientists had often looked for anatomical features that were optimized to produce vowels.

“This new study supports a growing consensus that vocal communication was a key part of Neandertals’ everyday life,” says Rebecca Wragg Sykes, an honorary fellow at the University of Liverpool in England and author of Kindred: Neanderthal Life, Love, Death and Art, who was not involved in the work. The ability to communicate, in her view, could have been quite sophisticated. “This new research shows Neandertals and early Homo sapiens likely spoke with broadly similar sounds,” she says, “implying that if attempts were made to talk during interbreeding phases, some common understanding of language [or perhaps an interspecies creole] might have been possible.”

This article originally appeared in Spektrum der Wissenschaft and was reproduced with permission.