Neuroscientists wrestle with human language even more than poets or (for example) English majors do. Its ability to enable us to handle abstractions seems a world apart from the grunts, whoops, and squeaks of the animal kingdom that simply express feelings or basic information.

Last year at Big Think, science writer Mo Costandi traced the difference to our “unique human brain structure” :

Speech is unique to humans, but most of the brain structures involved in speech production are also present in Old World monkeys and other nonhuman primates. The ventrolateral prefrontal cortex varies widely between these species, with one subregion being only partly developed in chimps and absent from Old World monkeys. Progressive evolutionary development of this subregion may be linked to the emergence of the improved vocal control needed to produce complex speech. 

“This unique human brain structure may have given us speech,” August 10, 2023

Note the Usage: “May Be Linked”

That’s a bit uncertain. Hardly one of the assured results of evolution studies. 

To complicate the picture, a study published later that year found that chimpanzee vocal development is not much different from that of humans:

New research has found that infant and juvenile chimps demonstrate a similar vocal flexibility, which implies the foundations for speech are rooted in our primate evolutionary heritage.

Lead author, Dr Derry Taylor, from the University of Portsmouth’s Department of Psychology, said: “All living things communicate, but only humans communicate using language. How this came to be is an unsolved mystery within science.

“Until now we didn’t have evidence of vocal functional flexibility in non-human primates early on. This discovery holds profound implications for our understanding of the origins of human language.”

The paper, published in iScience, is one of the first systematic studies of early chimp vocal production and function. University of Portsmouth. “New study reveals similarities between chimpanzee and human language development.”

Science Daily, October 17, 2023 The paper is open access.

As the authors say in their abstract,

All living things communicate yet only humans can be said to communicate using language. How this came to be the case is a fundamental mystery unsolved by contemporary science. Within a human lifetime, language emerges from a complex developmental process. As such, understanding chimpanzee vocal development is essential to understanding the evolutionary roots of language. In human development, language is directly built upon the early capacity for “vocal functional flexibility”—the ability to flexibly express the same vocalizations in different ways to achieve different functions. Primate vocalizations, by contrast, have long been believed to be relatively inflexible regarding both production and function. In this paper, we break new ground by providing evidence for vocal functional flexibility in one of the first systematic studies of early chimpanzee vocal production and function. This finding implies the developmental foundations for language are rooted in our primate evolutionary heritage. 

Derry Taylor, Erik Gustafsson, Guillaume Dezecache, Marina Davila-Ross. Vocal functional flexibility in the grunts of young chimpanzees. iScience, 2023; 26 (10): 107791 DOI: 10.1016/j.isci.2023.107791

Not a Physical Barrier but a Mental One

Despite the claim that “This finding implies the developmental foundations for language are rooted in our primate evolutionary heritage,” essentially, the researchers have demonstrated something quite different. They have found that young chimpanzees could learn human-level languages in principle — in the sense that they could perform the actions physically (“vocal functional flexibility”). But they simply don’t learn such languages.

As a find in evolution studies, this is a strikingly negative one. There is no physical limitation to chimpanzee speech; it is a mental one. Human language is full of abstractions (for example, Tuesday, 75 percent, nationalism, germ theory of disease…).

Chimpanzees learn how to express their feelings and possibly to communicate basic information about say, danger or food. But they apparently cannot get beyond that intellectually. The nature of the barrier has been made clearer by the recent research.

People who care about animals are probably not doing the chimps a favor by pretending that the difference is all something we are doing to them or don’t understand about them. If chimps don’t care about us, it doesn’t matter. But sadly, if we don’t care about them in a realistic way, they could go extinct outside of conservation areas.

We humans are exceptional whether we like it or not and we could at least use that fact for something good.

Cross-posted at Mind Matters News.