Final answer:
The stone heads are significant for their immense size, which reflects the Olmec society's organization and power, and for their individualized portrayal of rulers, demonstrating intricate artistry and personal depiction.
Step-by-step explanation:
The stone heads of the Olmec civilization are remarkable for two main reasons. Firstly, the colossal size and the effort required to transport and carve these massive basalt boulders from distant mountains are indicative of the complex organization and social structure of the Olmec society, emphasizing the power and influence of their rulers. Secondly, the unique facial features and individuality of each head suggest that they were likely intended as realistic portraits of individual rulers, rather than generic or symbolic representations. These factors contribute to the significance of the stone heads as a testament to the artistry, engineering, and hierarchical society of ancient Mesoamerica.