Peeling the Layers

I am picking another layer of skin off the Great Stemma at last. Yolanta Zaluska, in her study of the document, was the first to point out that large chunks of this Late Antique work have been copied from works by Isidore of Seville (c. 560 – 636). She described the longest recension, the Beta, as being fortement interpolé, en grande partie, semble-t-il, à l'aide des Etymologies d'Isidore. She was sketchy about the details, but thanks to full-text databases I have been able to track some of these borrowings down.
(1 It turns out that the Table of Nations material, which Zaluska says goes back to Josephus, is quoted practically verbatim from the 9th book of the Etymologiae. These glosses on the biblical ancestors of Mediterranean and Middle Eastern ethnic groups are uniform in both the Alpha and Beta recensions. (2) The so-called Recapitulatio comes from another book by Isidore, the Chronica Majora, a fact which Zaluska also noticed: On peut se référer par exemple à la Chronique d'Isidore, en part. n° 24, 26, 28, 30, 31a, 32a, 32; la phrase Belus pater Nini qui fecit Babiloniam n'est pas d'Isidore. The latter phrase could perhaps be a paraphrase of Isidore, who does insist that Ninus was the son of Belus. (3) Zaluska does not mention it, but a substantial passage dealing with Babylon's temples of precious stones and gold and the Tower of Babel has also been lifted from the Chronica and inserted into the chronology material of the Beta manuscript: perhaps she missed this. (4) Zaluska also considered the mappamundi in the Roda manuscript (Ro) and the Beta recension came from Isidore: Ro est très intéressant sur ce point car il interrompt le déploiement des tables à cet endroit et recopie autour de la mappemonde les textes des Étymologies d'Isidore qui s'y réfèrent: Orbis de rotunditate...; Asia ex nomine...; Post Asiam Europam...; Libia dicta... (Etym, lib. XIV, cap. II, III, IV et V), nous livrant ainsi la source principale de cette composition. She is perhaps right about this, but we will have to recheck the evidence. I will be looking for more borrowings as I go.
Naturally one should not exclude the possibility that it was Isidore who copied the material from the antecedent Great Stemma. However that seems implausible, since Isidore's material is not only much more comprehensive, but also seems to be drawn from a text-format source, perhaps the works of Jerome.
This analysis is important not only in explaining how the Great Stemma grew by accretion, but also in stripping off the accretions to get a picture of how it looked in the beginning. It is like peeling off the brown layers from an onion to get at the edible white interior.