Here's why:
* Biological Precursors: Humans have the biological capacity for speech, including vocal cords and a complex brain structure, long before the development of writing systems.
* Complexity of Language: Spoken languages are incredibly complex systems involving grammar, syntax, and nuanced meaning. It's unlikely writing systems emerged before these systems existed.
* Archaeological Evidence: The oldest evidence of spoken language comes from cave paintings and artifacts that suggest symbolic communication, dating back tens of thousands of years. The oldest known writing systems, like cuneiform, only emerged around 3500 BCE.
While spoken language came first, it's important to remember that the development of writing had a profound impact on the evolution of language itself. Writing provided a permanent record of language, allowing for the standardization of grammar and vocabulary, and the transmission of knowledge across generations.