There is an ancestral language shared by all great ape species, including us. A theory

One of the most important tools our species uses is certainly language, to whose learning we are innately adapted. For a series of advantages which I will not discuss here, but which are obvious, verbal language, based on vocal communication, is the privileged form of communication between human beings; however, it is certainly not the only one, and is often assisted by other forms of non-verbal communication – especially gestural.

This second form of communication is also characteristic of the great anthropomorphic apes: chimpanzees, for example, use hundreds of different gestures for their communication, and are also capable of composing sequences of gestures, the meaning of which depends on the individual gestures making up the sequence.

This ability, as well as in nature, has also been documented in chimpanzees who have been taught human sign language: specimens who are well versed in this form of communication, faced with new facts – such as the observation of a swan in a pond – correctly communicated what they were seeing by combining the signs for water and bird, demonstrating the typical flexibility of use of individual ‘words’ of a language when used in the appropriate combination.

Not only that: recently, it has been discovered that chimpanzees use gestures to communicate in ways that follow certain human linguistic rules. Over the years, linguists have discovered that human language conforms to specific rules regardless of the language in which it is spoken. One of these rules, Zipf’s law of abbreviation, corresponds to the fact that the most frequently used words tend to be short. Another rule is called Menzerath’s law: it states that larger speech structures tend to be separated by shorter segments when spoken.

The researchers found that the rules of human speech apply to chimpanzee use of gestures: the most commonly used gestures tend to be quite short, for example, and longer gestures are interrupted by multiple shorter gestures. This suggests that the basis of the communication systems of the examined non-human primates and humans follow the same basic mathematical principles, which tend to optimize compression as a function of speed of execution.

Given these elements, the question has recently been asked whether it could not exist a common form of sign language common among great apesthat is, whether at least anthropomorphic species are not able to communicate at least partially using gestures, without having previous experience of their meaning.

A recently published work seems to give substance to this hypothesis: humans retain an understanding of the gestures made by other great apes, even if we no longer use them ourselves. It was already known that many gestures used by apes were shared among non-human species, including only distantly related apes such as chimpanzees and orangutans.

In the new work, the researchers tested people’s ability to understand the 10 most common gestures used by chimpanzees and bonobos using an online game. More than 5,500 participants were asked to view 20 short videos of monkey gestures and to select the meaning of the gesture from four possible responses. It was thus discovered that the participants correctly interpreted the meaning of the gestures of chimpanzees and bonobos in a statistically better way than one might expect on the basis of chance, i.e. in over 50 percent of the cases (recall that the possible answers were 4 for each gesture).

The findings suggest that although we no longer use certain gestures, we may have retained an understanding of this ancestral communication system. It is unclear at this time whether our ability to understand specific great ape gestures is inherited or whether humans and other great apes share the ability to interpret meaningful cues due to their general intelligence, physical similarity, and shared social behavior.

Beyond the fact that it is genetically pre-established, the ability to correctly interpret (and use) certain gestures appears in any case to suggest the existence of an evolutionarily ancient gestural vocabulary shared among all species of great apes, including us; it is probable that the same communication system was also shared with other human species with which we have coexisted, thus providing a basis for hypothesizing how interspecific contacts could have occurred, which also led us to hybridization with species such as the Neanderthals, and at the same time the same way between these and the man of Denisova.

It is probable that we all understood a basic sign languagethe same which, for example, allows us today to communicate elementary concepts to those who do not understand our word and which we are able to grasp in the non-verbal communication of the non-human monkey species that still live today.