In the book, The Evolution of Calpurnia Tate, what is one quote that shows an important role in the story's development?

From the text:

"He extracted a book covered in rich green morocco leather handsomely tipped with gold. He polished it with his sleeve, although I could see no dust on it. Ceremoniously, he bowed and offered it to me. I looked at it. The Origin of the Species. Here, in my own house. I received it in both my hands. He smiled. Thus began my relationship with Granddaddy."