Did Human Ancestors Ever Use Sign Language Before Developing Spoken Language?
The idea that early human ancestors might have used some form of sign language before developing spoken language is a topic of considerable interest and debate among researchers. While there is no direct evidence of sign language being used by pre-linguistic humans, several points suggest that gestures could have played a significant role in early communication.
Evolutionary Perspective
Many primates, including our closest relatives like chimpanzees and bonobos, use gestures to communicate. This suggests that gestural communication may have been a precursor to spoken language in human evolution. The ability to use gestures to convey meaning likely emerged in an earlier form, providing a foundation for the complexity of language that would follow.
Cognitive Development
The development of complex cognitive skills such as the ability to understand and convey abstract concepts likely predates fully developed spoken language. Early humans might have relied on gestures to communicate these ideas, using manual signals to express abstract thoughts and emotions. Gestures could have been a more efficient and versatile way to communicate before the advent of spoken language.
Archaeological Evidence
Some archaeological findings such as cave paintings and artifacts suggest that early humans engaged in complex social interactions. Gestural communication could have facilitated these interactions before the advent of spoken language. The use of signs and symbols, even in rudimentary forms, could have paved the way for more sophisticated methods of communication as cognitive abilities developed.
Modern Sign Languages
The existence of fully developed sign languages today, such as American Sign Language (ASL) and others, demonstrates that sign language is a complete and effective means of communication. This suggests that if early humans used gestures, they may have developed into more structured forms of sign language over time. The development of sign languages today provides a blueprint for how gestural communication might have evolved into spoken language.
Social Interaction
The social nature of early human communities likely necessitated some form of communication. Gestures could have been a practical solution for coordinating activities, sharing information, and establishing social bonds. The need to communicate effectively in a group environment might have driven the evolution of both sign language and spoken language.
Conclusion
While there is no definitive evidence that human ancestors used sign language in the way we understand it today, it is plausible that gestural communication was an important aspect of their social interactions and may have preceded the development of spoken language. The interplay between sign language and spoken language suggests that these communication methods developed concurrently and independently, each building upon the other to enable the complex social interactions that define human society.
It is essential to recognize that while sign language and spoken language are different canals, they evolved in tandem. The evolution of speech, as we discuss in our article "Seafood Diving Song and Speech," shows that the various elements of human speech evolved at different times and originally had different functions.
Comparative Data: The Evolution of Human Speech
The evolution of speech is a complex process that involves multiple adaptations. Recent work by Nishimura [1-6] suggests that the laryngeal descent, commonly known as the descent of the thyroid cartilage (Adam's apple) relative to the hyoid bone, evolved in a mosaic way in minimally two steps:
Step 1: A descent of the thyroid cartilage (Adam's apple) relative to the hyoid bone is also seen in non-human hominoids (apes). This descent might be associated with the ability to produce louder and/or more varied sounds, which could be related to territories calls observed in apes.
Step 2: A descent of the hyoid bone relative to the palate, which is less obvious in non-human hominoids and is accentuated by the absence of prognathism (a flat, short face) in humans. This second descent may be part of an adaptation to eating seafoods like shellfish, which can be sucked into the mouth and swallowed without chewing even under water.
Comparisons with other animals suggest that:
The first descent might be associated with the production of louder and/or varied sounds.
The second descent might be part of an adaptation to eating seafoods, which could help explain why chimpanzees did not evolve language skills and why human language is a unique phenomenon.
We argue that the origin of human speech is based on different pre-adaptations that were present in human ancestors, such as:
Sound production adaptations related to the descent of the thyroid cartilage, similar to the territorial calls of apes.
Transformation of the oral and dentitional anatomy, including the descent of the hyoid bone, which might be related to reduced biting and chewing.
Diving adaptations leading to voluntary control of the airway entrances and voluntary breath control, which are key to the ability to hold one's breath under water.
Chimpanzee ancestors became frugivores in tropical forests after they split from human ancestors approximately 5 million years ago, while human ancestors became littoral omnivores. This difference in diet might help explain why chimpanzees did not evolve language skills and why human language is a unique phenomenon.
Understanding the evolution of sign language and speech in human ancestors is crucial for comprehending the complex nature of human communication. These early forms of communication likely played a pivotal role in shaping human social structures and cognitive abilities, paving the way for the development of spoken language.