Arguments for early sign language:
* Pre-language communication: It's widely believed that humans developed spoken language gradually. Before language evolved, early humans likely relied on gestures, facial expressions, and other nonverbal cues to communicate.
* Primate communication: Many primate species, our closest evolutionary relatives, use complex sign language systems. Observing these primates provides insight into the potential capabilities of early humans.
* Brain structure: Research suggests that the areas of the brain responsible for language and sign language are similar. This implies a shared evolutionary history and potential for both forms of communication.
* Visual communication in early humans: Early humans lived in environments where sounds could be easily obscured by foliage or noise. Visual communication may have been a more reliable way to convey messages.
* Cave art and symbols: Early cave paintings and symbols, like those found at Lascaux and Chauvet, suggest the development of visual communication and symbolic thought.
Arguments against early sign language:
* Lack of direct evidence: As mentioned, there is no direct evidence of early sign language use. It's difficult to definitively prove something from thousands of years ago.
* Limited evidence from fossil records: While fossil evidence can shed light on physical capabilities, it doesn't offer much information about early language or communication systems.
* Focus on spoken language: Much of the research on early human communication has focused on the development of spoken language, leading to a bias against other potential communication systems.
Conclusion:
While we cannot definitively say whether early humans used sign language, the arguments presented suggest that it is a plausible scenario. It's important to continue exploring this possibility through research and analysis of available evidence, like primate behavior, brain structure, and early art.
The study of human communication is ongoing, and new discoveries may shed more light on the role of sign language in the evolution of human communication.