Notice that these sentences even make sense when placed in their own paragraph:
It [the photograph] speaks about the more intimate details that first seem invisible but become undeniable through the study of gestures. In the photograph, the most prominent and symbolic of gestures is the use and position of the arms. Edwin's position in the photograph is indicative of him as a person, for he always seems to isolate himself from the spotlight, from being the center of attention. While Edwin stands apart from the other three figures, I stand enclosed and protected. Her [my mother's] grip, which proves more powerful than my father's hold, restrains not only me but also my father.
Obviously, Lee needs support for each of her topic sentences, but notice how the thesis and topic sentences provide a clear summary of the whole essay. As a reader reads the whole essay, then, the thesis and the topic sentences clarify the focus of the entire essay and the focus of each paragraph. They work together to keep Lee's inference and analysis clear and well-organized.