According to Bill Arnold, “the genealogies of Genesis have three functions. First, by means of a process known as “divergence,” each paragraph of ancient Israel is the father of other children who are not part of the Israelite ancestry and who become the ancestors of other people groups in the ancient world. Through such a process of differentiation, Genesis explains how Israel related to the other populations of the ancient world. Second, Israel’s lineage itself is traced through a straight line from Adam to Jacob in a process known as “invergence,” in which only one son continues the Israelite ancestry. This lineal descent gives way to twelve subunits in a single generation with the children of Jacob (Gen. 29:31–30:24, counting Dinah, the birth of Benjamin is recorded in 35:16–21), and from that point forward a third process, known as “segmentation,” becomes primary. With the children of Jacob, the genealogies of Genesis focus on the branches of the ancestral family, all considered within the covenant blessing of Israel’s ancestry. Thus, the book traces through this system of genealogies a line of descent for all humanity through twenty-five generations from Adam to the children of Jacob, creating a literary framework or skeleton for the entire book."
Bill T. Arnold, “The Genesis Narratives,” in Ancient Israel’s History: An Introduction to Issues and Sources, Bill T. Arnold and Richard S. Hess, eds. (Grand Rapids: Baker, 2014), 32-33.