There is no difference between "And the sons of Ham were Cush, Mizraim, Phut, and Canaan" (Genesis 10:6), "And his wife's name was Mehetabele, the daughter of Matred, the daughter of Meizahav" (Genesis 36:39), "And Timna was concubine to..." (Genesis 36:12), and "I am God, your Lord, who brought you out of the land of Egypt" ( Deuteronomy 5:6), and "Hear O Israel, God is our Lord, God is One" (Deuteronomy 6:4).
(translation of this and all ikkarim on my blog taken from R. Mordechai Blumenfeld)
- They are there because it is a feature of ANE (ancient near east) literature. Put into more traditional terms, it is lishna be-dei adam, in common language.
- It is very relevent, but its relevence has yet to be discovered. As far as I know this was the case with the extensive Biblical geography which proved very useful in modern Israel in understanding the land of Israel, in warfare and in industry. Maybe in the future the geneologies will be useful.
- The geneologies and the like are part of shaping a Torah-influenced worldview. We are "Semites". Ancient Mesopatamia, hosted the cradle of civilization, Sumer (Shinar) and so forth. Maybe these lists are there to give Biblical names and markers for things to the world, so that it be influenced by the Bible even more.
- It's a "test of faith" of sorts. It is there in the sense of the idomatic expression "from A to Z", with Z seeming less important, but as in an alphabet, still necessary.
1 doesn't seem adequate, 2 is unproven, 3 is a little compelling to me and 4 makes no sense, but it just came out of my keyboard. ;)
Edit: I thought of a 5th reason. Maybe these lists are a reinforcement of the injunction to "Remember the days of old, Consider the years of ages past" (Deuteronomy 32:7).
A 6th reason which people might posit is that deep sodos are hidden in these lists. That one is really an adjunct of reason 2 though.