Final answer:
The development of West African societies was profoundly influenced by trade, which facilitated economic growth and the spread of culture. Ironworking technology was independently developed in sub-Saharan Africa and revolutionized agriculture, crucial for societal expansion. Although all factors are intertwined, the spread of ironworking had a direct and significant impact.
Step-by-step explanation:
When examining the factors that were most important for the development of early West African societies, trade emerges as a key element. It was through trade that West Africa connected with other regions. The trade in gold, salt, and slaves not only facilitated economic growth but also helped in the dissemination of culture, religion, and technology. This economic activity led to the establishment of powerful city-states, kingdoms, and empires, which grew wealthy by taxing trade. While geography played a role in where and how societies developed, and the specialization of labor allowed for more efficient production, it was ironworking that revolutionized agriculture by introducing stronger farming tools. The spread of ironworking technology was critical, but it was independent innovation rather than diffusion from outside groups that best explains this phenomenon in sub-Saharan Africa. This technology allowed for more efficient land clearing for agriculture and thus the expansion of Bantu-speaking peoples, who utilized these advancements. However, considering the complexities of early West African development, it's the combination of trade, agricultural advancement through ironworking, and strategic geographical utilization that provided a synergistic effect leading to societal growth. Therefore, while trade played a transformative role, the question could be understood as which single factor stands out, and in light of historical evidence, the spread of ironworking technology appears to have had a profound and direct impact on early West African societies.