I am not ashamed of my grandparents for having been slaves. I am only ashamed of myself for having at one time been ashamed. (1.2)
Speaking from the novel's present (i.e., in the manhole), the narrator acknowledges that he is no longer ashamed of his grandparents' slave background, indicating a desire to fully accept his past.
They were all such a part of that other life that's dead that I can't remember them all. (Time was as I was, but neither that time nor that "I" are any more.) (2.7)
The story the narrator is about to tell is a story regarding a (metaphorical) previous incarnation of himself – it concerns someone the narrator used to be.
I took a bite, finding it as sweet and hot as any I'd ever had, and was overcome with such a surge of homesickness that I turned away to keep my control. I walked along, munching the yam, just as suddenly overcome by an intense feeling of freedom – simply because I was eating while walking along the street. It was exhilarating. I no longer had to worry about who saw me or about what was proper. To hell with all that, and as sweet as the yam actually was, it became like nectar with the thought. If only someone who had known me at school or at home would come along and see me now. How shocked they'd be! I'd push them into a side street and smear their faces with the peel. What a group of people we were, I thought. Why, you could cause us the greatest humiliation simply by confronting us with something we liked. Not all of us, but so many. (13.24)
For the narrator, eating yams in the street is not just eating yams in the street, but an embrace of his past and his heritage. While formerly he never would have eaten yams in public the way other black people did, the narrator experiences a newfound freedom to openly appreciate traditionally black food. (Contrast this to his angry refusal of the pork chops and grits special in the diner.) This passage is a throwback to a famous scene in Marcel Proust's Remembrance of Things Past where the author bites into a Madeleine and is transported to his childhood.
You must realize immediately that much of our work is opposed. Our discipline demands therefore that we talk to no one and that we avoid situations in which information might be given away unwittingly. So you must put aside your past. (14.120)
This demand reflects the Brotherhood's insistence on the sacrifice of individuality.
That was all I needed, I'd made a contact, and it was as though his voice was that of them all. I was wound up, nervous. I might have been anyone, might have been trying to speak in a foreign language. For I couldn't remember the correct words and phrases from the pamphlets. I had to fall back upon tradition and since it was a political meeting, I selected one of the political techniques that I'd heard so often at home: The old down-to-earth, I'm-sick-and-tired-of-the-way-they've-been-treating-us-approach. I couldn't see them so I addressed the microphone and the co-operative voice before me. (16.36)
This further illustrates the difference in political philosophy between the narrator and the Brotherhood. He rejects the Brotherhood's approach to speech-making and is a huge hit when he chooses to use the political traditions with which he grew up. When push comes to shove, when the narrator stands in front of a giant spotlight and a huge crowd, he resorts to lessons from his past.
I looked at the dark band of metal against my fist and dropped it upon the anonymous letter. I neither wanted it nor knew what to do with it; although there was no question of keeping it if for no other reason than that I felt that Brother Tarp's gesture in offering it was of some deeply felt significance which I was compelled to respect. Something, perhaps, like a man passing on to his son his own father's watch, which he accepted not because he wanted the old-fashioned timepiece for itself, but because of the overtones of unstated seriousness and solemnity of the paternal gesture which at once joined him with his ancestors, marked a high point of his present, and promised a concreteness to his nebulous and chaotic future. And now I remembered that if I had returned home instead of coming north my father would have given me my grandfather's old-fashioned Hamilton, with its long, burr-headed winding stem. (18.70)
Not only does this passage indicate Brother Tarp as a father figure, Tarp's gift to the narrator evokes his own past and the traditions of continuity embedded within the passing down of a gift.