Final answer:
The discovery of obsidian at a prehistoric site indicates the existence of trade networks, providing material mined as far as 200 miles away.
Step-by-step explanation:
The discovery of obsidian at a prehistoric site indicates the existence of trade networks, providing material mined as far as 200 miles away. Obsidian could be chipped to create sharp tools and weapons, which were traded for other goods with other towns and villages. Examples of this can be seen in sites like Catal Huyuk and Çatalhöyük, where obsidian tools have been found far from their origins, indicating long-distance trade networks.