Genealogies are important for a number of reasons. They serve a number of functions, it seems. One of them was to establish sociopolitical ties through expressing fictive kinship ties. So, perhaps the most well known example would be with respect to the twelve tribes; you have the birth narratives of the sons of Jacob, who is “Israel” in
The list that appears in Numbers differs from the list that appears in Deuteronomy; and there is another list that appears in Judges 5, which is quite different from the others. Tribes drop in and out; Levi is not in all of the lists; Simeon is not in all of the lists. Ephraim and Manasseh are the sons of Joseph and Joseph is not in any of the lists; and so, they reflect different time periods and different relations among people; that’s one function.
Another function is just establishing social roles. Genealogies are important in Chronicles and probably reflects the period of returning after the exile and rebuilding and so, the establishing and reestablishing of social roles was important, and genealogies played a role in that.
Then there’s the aspect of genealogies that is more a literary framing device. So, it’s an ancient genre; it probably has oral roots. We know genealogies from Mesopotamia, forms from Egypt, from Greece as well. And often these early genealogies connect the divine world with the human over the course of time. And so, this is what seems to appear in Genesis when you have the creation narrative given and then, a statement that this is the genealogies, this is the generation, toledot of the heavens and the earth. And that phrase is repeated, this is the toledot, these are the generations of one thing or another as it becomes more and more specific down to the people of Israel from the most general creation, God, etc.