Human speech might have a long history of at least 25 million years. This perception has dawned after the analysis of a slew of baboon calls that hold clues to the evolution of human speech and extend the building blocks of language to the early non-human primates.
The researchers of the National Center for Scientific Research and Grenoble Alpes University in France analyzed the yaks, barks, and wahoos, and other sounds baboons made. They conducted tests on guinea baboons in captivity and saw them making vowel-like sounds despite the high voice boxes that would have impeded the speech.
The belief so far had been that vowel sounds can only be produced by humans as they have a low vocal box or larynx. The theory around human speech has been that a low larynx is a must to produce a variety of vowel sounds and is the precondition for spoken language.The researchers found that the baboons can produce five distinct sounds of a similar frequency as human vowels.
With baboons being able to produce as many as five vowel sounds in their calls, scientists are now rethinking when human speech started. The study suggests the roots of human speech could go beyond more than 100,000 years, the history of human species, and date back to the primate family tree and a common ancestor.
"This confirms that hominoids can produce contrasting vowel qualities despite a high larynx. It suggests that spoken languages evolved from ancient articulatory skills already present in our last common ancestor with Cercopithecoidea, about 25 [million years ago]," the researchers wrote in their study, which was published in the journal PLOS One on Jan. 11.
Since the study of speech cannot rely on fossil imprints as spoken words have no geological record, the focus of the analysis was on the mouths of from where the sounds are produced.
"[S]peech also engages anatomical traits that might leave fossil clues, as well as overt anatomical, physiological, and behavioral aspects for which parallels can be sought in living primates," said the authors.
By comparing mouths of humans and their close relatives, researchers drew conclusions on traits necessary for the speech in humans and also the physical characteristics that block it.
Breaking The Logjam
Coauthor Thomas Sawallis deemed the findings as equivalent to the breaking of "a serious logjam" in the study of language. The linguist from the University of Alabama noted that language evolution theories were working on the premise that full speech was only available to modern Homo sapiens approximately 70,000 to 100,000 years ago.
Now it appears that "we could have had the beginnings of speech 25 million years ago," he added.
In the first phase of the study, the researchers recorded baboon vocalizations for many months and analyzed the recorded calls to trace formants, or frequencies of sound that had distinct characteristics of vowels.
During the tests with baboons, linguist Louis-Jean Boë recorded the vocalizations of 15 guinea baboons in which three were male and 12 female. Their spontaneous vocalizations included grunts, barks, "wahoos," yaks and copulation calls.
This was followed up by measuring the vocal tracts of baboons to understand how the animals produce different kinds of vowel-like sounds for communicating varied messages, including calls to mate.
"We know that any tube can make something that looks like a vowel. But what is the difference here is that we have five," said Joël Fagot, coauthor and a cognitive scientist at the French National Center for Scientific Research.
However, Fagot noted that "to be able to speak, you need much more than this." For instance, one essential faculty for speech is cognitive ability.
"But clearly they seem capable of at least having some of the building blocks of speech, which is the ability to form vowel-like sounds," Fagot said.
Basically, the production of vowels involves manipulating the vocal tract, which is difficult for animals with a different anatomy, explained Thore Jon Bergman, a biopsychologist at the University of Michigan.
The study is a landmark as it may change scientists' ideas of how human speech evolved.
If the condition that a low larynx was a prerequisite for speech, then the roots of human speech would be limited to when the modern Homo sapiens came about, which was some 100,000 years ago. On the other hand, if the new studies are taken note of and vocal anatomy restraint is overlooked, it is possible that the early blocks of human speech might have taken shape long before that.
The new findings are certain to bolster a recent study by Tecumseh Fitch of the University of Vienna in which an X-ray analysis of macaque vocal anatomy backed by computer models showed that animals can produce human-like speech sounds.