The concept of biblical authors using sources (particularly other biblical sources) is disconcerting to some people. This is not an altogether irrational fear, given the way liberals have often misused the idea to set biblical authors against each other, fragment the text to death, and ignore the final literary products of the various books of the Bible. That said, biblical authors did at times use other biblical works as sources, and careful analysis of apparently synoptic passages can be of great text-critical value.
My recent reading in 1 Chronicles 1 brought this consideration to the forefront of my mind, as I consistently found very precise correspondence between the genealogies of 1 Chronicles 1 and Genesis 10, not just in the names used, but even in very specific examples of precise correspondence of wording and syntax in narrative comments that seem to demand literary dependence. A few indicative examples will suffice to show that the Chronicler was using the text of Genesis as his source:
1) וְכ֖וּשׁ יָלַ֣ד אֶת־נִמְר֑וֹד ה֣וּא הֵחֵ֔ל לִהְי֥וֹת גִּבּ֖וֹר בָּאָֽרֶץ׃ "And Cush became the father of Nimrod; he began to be a mighty one in the earth." (1 Chr 1:10 = Gen 10:8)
2) וּכְנַ֗עַן יָלַ֛ד אֶת־צִיד֥וֹן בְּכֹר֖וֹ וְאֶת־חֵֽת׃ "And Canaan begat Zidon his firstborn, and Heth," (1 Chr 1:13 = Gen 10:15)
3) וּלְעֵ֥בֶר יֻלַּ֖ד שְׁנֵ֣י בָנִ֑ים שֵׁ֣ם הָאֶחָ֞ד פֶּ֗לֶג כִּ֤י בְיָמָיו֙ נִפְלְגָ֣ה הָאָ֔רֶץ וְשֵׁ֥ם אָחִ֖יו יָקְטָֽן׃ "To Eber were born two sons: the name of the one was Peleg (for in his days the earth was divided), and his brother's name was Joktan." (1 Chr 1:19 = Gen 10:25).
If the Chronicler was indeed using Genesis as his source, this means that 1 Chronicles 1 can be used as a textual witness to the text of Genesis 10 at points where the latter reproduces the former (while, of course, taking into account the possibility that the Chronicler could have adapted the material to fit the context of his own work). Thus, to the traditional witnesses to Genesis (MT, SP, G, Targums, Vulgate, Syriac, etc.) must be added 1 Chronicles. Admittedly, the text of Chronicles itself has undergone over two millennia of transmission and so must likewise be critiqued before being useful for reconstructing the text of Genesis, but an ancient witness it still is.
This brings us to one example textual problem in 1 Chronicles 1:7 || Genesis 10:4, where one of Yavan's sons (or tribe of descendants) is named variously Dodanim דֹדָנִֽים and Rodanim רוֹדָנִים, where the variants obviously arose from graphic confusion of the very similar first letter ד/ר. And given the literary dependence and content parallels, both obviously refer to the same person, so only one of them can be correct. The textual evidence among the major sources looks as follows:
Dodanim = דֹדָנִֽים MT(Gen 10:4)
Rodanim = רוֹדָנִים MT(1 Chr 1:7) SP (Gen 10:4) G (Ρόδιοι, Gen 10:4 and 1 Chr 1:7)
The majority Masoretic witness is divided in the two places. It is unlikely that the Samaritan Pentateuch and Septuagint would have assimilated the Genesis text to fit the 1 Chronicles reference. Thus many have concluded that the text of Genesis 10:4 originally said Rodanim רֹדָנִים instead of Dodanim דֹדָנִֽים and have emended the text accordingly (e.g., NRSV, NIV, NLT, and also I suspect is correct). Others have chosen Dodanim as the proper name in both cases (e.g., KJV). But many translators have chosen to represent the discordant majority MT readings in both cases, saying in Gen 10:4 that his name is Dodanim and in 1 Chr 1:7 Rodanim (e.g., RSV, NAS, NKJV, ESV, NET Bible). In my view, this latter option is entirely irresponsible and shirks the translators' responsibility to present a critically sound and coherent text. The man's name (or tribe's name) is either Dodanim or Rodanim, and not both, and the Bible translators who maintain the majority MT reading in both cases do a disservice to their readers out of a misguided faithfulness to the (in this case) textually corrupt MT. The church is better served with an accurate text than with a traditional text, and textual criticism, taking into account synoptic passages, can help us get there.