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. 2003 Jul 22;100(15):9079-84.
doi: 10.1073/pnas.1331158100. Epub 2003 Jul 1.

Toward a Phylogenetic Chronology of Ancient Gaulish, Celtic, and Indo-European

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Toward a Phylogenetic Chronology of Ancient Gaulish, Celtic, and Indo-European

Peter Forster et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

Indo-European is the largest and best-documented language family in the world, yet the reconstruction of the Indo-European tree, first proposed in 1863, has remained controversial. Complications may include ascertainment bias when choosing the linguistic data, and disregard for the wave model of 1872 when attempting to reconstruct the tree. Essentially analogous problems were solved in evolutionary genetics by DNA sequencing and phylogenetic network methods, respectively. We now adapt these tools to linguistics, and analyze Indo-European language data, focusing on Celtic and in particular on the ancient Celtic language of Gaul (modern France), by using bilingual Gaulish-Latin inscriptions. Our phylogenetic network reveals an early split of Celtic within Indo-European. Interestingly, the next branching event separates Gaulish (Continental Celtic) from the British (Insular Celtic) languages, with Insular Celtic subsequently splitting into Brythonic (Welsh, Breton) and Goidelic (Irish and Scottish Gaelic). Taken together, the network thus suggests that the Celtic language arrived in the British Isles as a single wave (and then differentiated locally), rather than in the traditional two-wave scenario ("P-Celtic" to Britain and "Q-Celtic" to Ireland). The phylogenetic network furthermore permits the estimation of time in analogy to genetics, and we obtain tentative dates for Indo-European at 8100 BC +/- 1,900 years, and for the arrival of Celtic in Britain at 3200 BC +/- 1,500 years. The phylogenetic method is easily executed by hand and promises to be an informative approach for many problems in historical linguistics.

Figures

Fig. 1.
Fig. 1.
Living and extinct languages referred to in this study.
Fig. 2.
Fig. 2.
Construction of the linguistic network. Thick broken lines indicate splits to be introduced in the following step. Character states az are taken from Table 1. Characters (e.g., SV, cintux) are entered perpendicularly to their links. Parallel links in a reticulation (here, a square or cube) signify the same character. The end result is shown in Fig. 3.
Fig. 3.
Fig. 3.
Phylogenetic network of ancient and modern Indo-European languages. The items are noted in Gaulish, for translations consult Table 1. The asterisked node denotes the putative Indo-European rooting in the network. The network method produced the full network, from which the broken lines have been subsequently removed by hand. The remaining unbroken lines indicate the putative Indo-European tree that we chose for time estimations. As an illustration of how to read the tree, consider Spanish, which differs from Latin by the items “duxtir” (daughter), “luxtodos” (loaded), “-as” (genitive singular feminine suffix), and the phoneme “ps.” In Latin, the state for duxtir is “filia,” which according to the network has mutated to the state “hija” in Spanish, in agreement with etymological considerations. The genitive suffix has mutated from Latin to Spanish by being lost, likewise the phonetic item. The luxtodos item (“oneratus” in Latin and “cargado” in Spanish) on the other hand has mutated by outright replacement.
Fig. 4.
Fig. 4.
Lexeme distance tree extracted from the Indo-European network of Fig. 3. The branch lengths are normalized to AD 2000 for the dead languages, assuming 1 lexeme exchange per 1,350 years on average.

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