Peter and Rosemary Grant are British evolutionary biologists at Princeton University known for their landmark study of the finches of the Galápagos. Initially, Peter led the study and Rosemary handled logistics, but they now maintain an equal research partnership. In life and throughout the text, they function as a unit, as a colleague explains: “The world will take much of what they do as Peter. Yet they really do something that transcends either one of them” (119). Because The Beak of the Finch anchors its expansive exploration of evolution in the narrative of their work, Peter and Rosemary act as twin protagonists in a tale of discovery that at times feels like an adventure novel.

Weiner characterizes the pair in different moments as brave adventurers on a desert island, devoted shepherds of their birds, and imaginative theorists buried in their data. However, the Grants’ development as individuals does not drive the storytelling, and the text does not hinge on their personal transformation. Beyond being used to engage the reader in the content, they function more as guides, as Weiner often elucidates complex concepts for the reader in the Grants’ cheerful voices.