Final answer:
The provided excerpts do not directly mention the main topic of conversation on the store's porch in 'Their Eyes Were Watching God', but the conversations often center around daily life and social dynamics, reflective of African-American culture.
Step-by-step explanation:
In Zora Neale Hurston's novel Their Eyes Were Watching God, the main topic of conversation on the porch of the store isn't explicitly detailed in the provided excerpts. However, Hurston's work often focuses on the life and self-discovery of African-American women in early 20th century America. The protagonist, Janie Crawford's, journey from a dependent young girl to a self-actualized woman is a central theme of the novel. Conversations on the store's porch typically serve as a communal space for discussing the daily lives and social dynamics of the characters in the novel, reflecting the African-American culture and experiences of the time.