1. Fossil Evidence:
* Brain size: The brains of early Homo sapiens, who lived during the Old Stone Age, were significantly larger than those of their ancestors. This suggests an increase in cognitive capacity, which likely included language abilities.
* Hyoid bone: The hyoid bone, located in the neck, is crucial for speech production. Analysis of hyoid bones from Neanderthals, who lived in the Old Stone Age, indicates they were capable of vocalizing and potentially speaking.
2. Archaeological Evidence:
* Symbolic behavior: Art, tools, and burial practices from the Old Stone Age suggest complex thought processes and the ability to communicate ideas. These actions require a sophisticated system of communication, likely language.
* Complex toolmaking: The development of complex stone tools in the Old Stone Age demands planning, cooperation, and the ability to communicate complex ideas, likely through language.
3. Linguistic Evidence:
* Language universals: All human languages share fundamental features, suggesting a common origin. These universals point to a deep evolutionary history for language.
* Language evolution: The study of how languages change over time shows that languages evolved gradually, with roots stretching back thousands of years.
4. Cognitive Science:
* Brain regions: Studies of brain activity reveal dedicated areas for language processing in the human brain, suggesting an evolutionary predisposition for language.
* Chimpanzee communication: While not language in the same sense as humans, the complex communication systems of chimpanzees show that our primate ancestors likely had some capacity for communication.
5. Comparative Biology:
* Genetic evidence: Studies of genes involved in language production, such as the FOXP2 gene, reveal that language likely evolved in a relatively short period, potentially during the Old Stone Age.
While the exact origins of language remain a mystery, these lines of evidence strongly suggest that it developed during the Old Stone Age, at least in its rudimentary form. It's important to remember that language likely evolved gradually over time, with early forms likely being much simpler than the languages we speak today.