Final answer:
Early humans turned to the sea because of the sea's proximity and the lands' poor soil quality, which drove them towards marine-based food resources and opportunistic trade.
Step-by-step explanation:
The two factors that forced early men to the sea as fishermen and traders were the nearness of the sea and the limited fertility of the land. Due to the challenging terrestrial conditions, such as poor, rocky soil and a lack of large fertile areas like those offered by great rivers, early humans found that the sea offered a more reliable and abundant source of food and materials. The availability of sea life such as fish, shellfish, and seals provided a staple in their diet, while the sea itself became a means for trade and economic opportunity.