In the previous chapter, we argued that procedural problems inherent in the Gray–Atkinson approach, such as subjective and inconsistent selection of words for Swadesh lists and undiagnosed borrowings, have a significant warping effect on the resulting shapes of its linguistic family trees. In this chapter, we show that such errors also have a major effect on dating the origin and differentiation of the Indo-European family tree. More generally, we address the question of whether the branching patterns– and especially the Proto-Indo-European (PIE) root– can be dated by linguistic means. But before we proceed, we need to clarify what we mean by the timing of PIE or of any node on a family tree: it is the time just before the diversification of the ancestral language began. The ancestors of those Indo-Europeans that we seek to locate in time (and place, as discussed in subsequent chapters) might have spoken (an earlier form of) PIE and might have lived in some other location, but the history and geography of such ancestral groups is irrelevant for resolving the Indo-European debate. Ultimately, the most distant ancestral language of PIE speakers traces back to the cradle of humanity somewhere in Africa, but that too is beside the point.
Contrary to Gray–Atkinson’s claim that (traditional) historical linguists “don’t do dates”, the issue of dating lies at the core of historical linguistics as the very fact of language change implies“before” and “after”, “earlier” and “later” phases. However, most historical linguists remain highly skeptical about the possibility of attaching absolute and precise dates to language divergence events, as indicated by such article titles as “Why Lexicostatistics Doesn’t Work: The ‘Universal Constant’ Hypothesis and the Austronesian Languages” (Blust2000), “On the Uselessness of Glottochronology for the Subgrouping of Tibeto- Burman” (Matisoff2000), and“Why Linguists Don’t Do Dates: Evidence from Indo-European and Australian Languages” (McMahon and McMahon 2006). As Dolgopolsky (2000: 404) summarizes the skeptic’s view:
we cannot help concluding that the lapis philosophorum of glottochronology is unable to transmute the baser metals of lexicostatistical numbers into pure gold of reliable dating. The radiocarbon method of dating is good for atoms, but is not good for culture- bound human languages.
Although scholars working within the Gray–Atkinson approach deem this view “pessimistic” (Gray et al. 2011: 1090), we think a certain degree of skepticism about precise dates is the more realistic position. Advocates of Bayesian dating methods’ contrasting claim is that their approach is more scientific, as science involves getting things partly wrong and then refining the methods until they get things right. We, however, concur with McMahon and McMahon (2006: 159–160) that it is “quite unscientific to persist in attempting to date language splits when we do not have enough information to know whether and how far we are wrong. Any attempts to refine our methods and measurements in those circumstances can be no more than stabs in the dark.” In the following pages, we examine the development of linguistic methods of dating nodes on a family tree, ranging from lexicostatistics and glottochronology to the cutting-edge Bayesian phylogenetic dating methods employed by the Gray–Atkinson approach, highlighting the shortcomings of various techniques. In subsequent chapters (particularlyChapter 8), we turn our attention to the ways in which historical linguists working within the comparative method have been able to establish relative chronologies and, in some cases, absolute dates as well.
The rise and demise of glottochronology
The first attempts to “do dates” (in the Gray–Atkinson sense) in historical linguistics go back to the 1950s when Morris Swadesh developed an approach known as lexicostatistics that in turn gave rise to“glottochronology” (Swadesh
1952,1955).1Lexicostatistical methods infer language trees on the basis of the percentage of shared cognates between languages – the more cognates the languages share, the more closely related they are thought to be. But when it comes to dating the tree, lexicostatistical approaches can only provide relative chronologies, determining which splits happened before or after other splits. Glottochronology extends lexicostatistics by estimating language divergence dates under the assumption of a“glottoclock”, or constant rate of language change (for a more detailed introduction to glottochronology, see Lees1953). Swadesh examined changes in languages for which we have historical docu- mentation covering more than a thousand years: from Latin to the Romance languages, from Ancient Greek to Modern Greek, and from Sanskrit to the modern Indo-Aryan languages. For the Swadesh-200 list, the 1,000-year
1
Although often referred to as the linguistic analog of the“molecular clock” idea in biology, glottochronology was actually developed a full decade before Zuckerkandl and Pauling (1962) introduced the idea of using the divergence of molecular sequences to date biological lineages. Instead, the idea of a constant rate of lexical change must have been inspired by earlier work on radioactive decay.
retention rate (i.e. the expected proportion of cognates remaining after a millennium of separation) was found to be 86 percent; in other words, only 14 words out of 100 would be replaced over such a span of time. This method supposedly allowed Swadesh and his followers not only to measure the degree of relatedness between languages, but also to estimate the absolute date when their common ancestor split into daughter branches. For example, English and Russian share 34 percent of lexemes in the Swadesh-100, which would imply that their common ancestor split into the Germanic and Slavic branches approximately 4,000 years ago.
This apparently simple and elegant method was challenged as early as the 1960s and by now has been all but discredited; Dixon (1997: 49) thus referred to it as “the chimera of glottochronology”. The chief objection, raised first by Bergsland and Vogt (1962), is that languages do not actually evolve at a constant pace. Unlike sub-atomic changes or mutations in genes, which happen at random, changes in language are often precipitated by extra-linguistic, social factors. As a result, lexical replacements in the core vocabulary often happen in waves, and as a result the rate of replacement may differ radically from one language to another and from one period of time to another. Comparing extant languages with their archaic forms, Bergsland and Vogt found consider- able evidence of rate variation between languages. Their classical example involves two modern Scandinavian languages: Icelandic and Norwegian, both descendants of Old Norse, spoken roughly a thousand years ago. Norwegian retained 80 percent of the vocabulary of Old Norse, correctly suggesting an age of approximately 1,000 years. Icelandic, however, has retained over 96 percent of the Old Norse vocabulary, falsely suggesting that it split from Old Norse just over 200 years ago.2 Other similar examples abound. For instance, Blust (2000) documented variation in the rate of basic vocabulary retention ranging from 5 to 50 percent in the approximately 4,000-year period from the emergence of Proto-Malayo-Polynesian to the present. He concludes that these huge differences in retention rates inevitably distort both the trees obtained by lexicostatistics and the dates given to the nodes on the tree by glottochronological analysis. For the Austronesian languages considered by Blust, population size is one of the key factors behind such variation in retention rates. But while population size has been frequently argued to affect rates of change, no agreement has been reached as to whether the pace of
2
The Russian linguist Sergei Starostin proposed distinguishing between“internal replacements” (i.e. when a word is replaced by another word which already existed in the language but had a different meaning; e.g. in Russian the word brjuxo ‘belly’ was replaced by život, which originally meant‘life’) and “external replacements” (i.e. borrowings). Furthermore, he showed that if loanwords are eliminated from the calculations, the rate of change becomes more constant, approximately 5 percent per millennium. The problem, however, is that loanwords can never be perfectly diagnosed and eliminated, as discussed in theprevious chapter.
linguistic change in smaller linguistic groups is faster (Nettle 1999, 2000a,
2000b) or slower (Milroy and Milroy 1985, 1992; see also Bowern 2010). Although population size is less relevant to the Indo-European family, another overarching factor comes into play: language contact. Thus, a more isolated Icelandic retained more of the Old Norse vocabulary than Norwegian did. And as we shall see below, different rates of borrowing, which result in different cognate retention rates, plague the modern Bayesian methods used to date phylogenetic trees as well.
Bayesian phylogenetic methods for dating linguistic trees Since traditional glottochronology, based on the idea of “glottoclock”, has been rejected, new approaches to dating linguistic trees have been developed, based largely on Bayesian methods. One approach, pioneered by Sanderson (2002), is based on the idea of“calibration points” – that is, nodes on the trees that can be constrained to a known date range: relative branch lengths, which are proportional to the number of changes, are converted into time intervals based on the timing of these calibration points. Without relying on a strict clock, this method allows date estimation based on a combination of calibra- tions, branch-length estimates, and the rate-smoothing algorithm that penalizes trees in which the rates vary too much from branch to branch. An alternative approach, the so-called“relaxed phylogenetics” method, developed by Drum- mond et al. (2006), estimates the tree and the dates simultaneously. Bouckaert et al. (2012) use a modified version of this latter method.
The proponents of the Bayesian phylogenetic dating methods recognized the dangers of distortion due to both misshapen trees (e.g. because of high levels of borrowing) and mistaken calibration points. Their main response has been to argue that their methods produce tree topologies that are“robust to realistic levels of borrowing in basic vocabulary (0–15%)”, while allowing that their inferences about divergence dates are“slightly less robust and showed a ten- dency to underestimate dates” (Gray et al.2011: 1095). Elsewhere Atkinson and Gray reiterate their contention that“widespread borrowing can bias divergence time estimates by making languages seem more similar (and hence younger) than they really are” (Atkinson and Gray 2006: 92, italics ours). In other words, while conceding that their dating of PIE may be biased by undetected borrowings, they maintain that if it is, PIE must be even older than their model indicates, not younger, as maintained by adherents of the more generally accepted Steppe theory.
However, other studies suggest that dates produced by the Bayesian phylo- genetic dating methods are over- rather than underestimated. Three factors can contribute to making the root of the Indo-European tree look older than it actually is. Thefirst factor, undetected borrowing, along with related procedural
issues, has been shown to distort the shape of the tree inChapter 4. Recent work shows that such difficulties pose major problems for dating the tree as well. For example, McMahon and McMahon (2006) reconsider the study done by Forster and Toth (2003) andfind that the dates calculated by these research- ers for the PIE root (81001900 bce) and for the Celtic split (32001500 bce) deviate significantly from the dates expected from historical evidence, or obtained by other dating methods. This discrepancy is due in part to “an accumulation of minor errors due to borrowing, misclassification, or poor selection of meanings” (McMahon and McMahon2006: 158) – that is, the same problems that distort the shape of the tree, as discussed in theprevious chapter. Crucially, McMahon and McMahon conclude that undetected borrowing results in conclusions in which “the time depth of the family will have been artificially extended, pushing the original split of Celtic earlier than was in fact the case” (2006: 158–159, italics mine).
Going back to the Gray–Atkinson model, languages that are known to be particularly prone to borrowing are consistently erroneously dated as having diverged earlier than they actually did. Examples of this pattern are numerous; we shall limit ourselves to only two of them here. The most glaring blunder concerns Romani: not only is Romani mistakenly taken to have split off from the rest of the Indo-Aryan branch before any other language, as discussed at length inChapter 4, the date of the Romani split is wrong as well. Bouckaert et al. (2012) place it around 1500bce (3,500 years ago); linguistic evidence, however, suggests a much later date of around 1000ce (1,000 years ago).3 As mentioned inChapter 3, a number of grammatical changes that characterize the transition from Middle Indo-Aryan (MIA) to New Indo-Aryan (NIA) languages that happened circa 1000 ce, and which are shared by Romani, show that Romani could not have separated from the other Indo-Aryan lan- guages before that time. One such change, mentioned inChapter 3, is the loss of the neuter gender and the reassignment of the formerly neuter nouns to either masculine or feminine gender. This change encompassed Romani as well, which has only two genders, masculine and feminine (Matras2002: 72). Crucially, almost all of the formerly neuter nouns in Romani were reassigned to the same gender as their cognates in other NIA languages, such as Hindi. For instance, the neuter agni‘fire’ in MIA became the feminine āga ‘fire’ in Hindi and the likewise feminine jag in Romani. Given that there are several dozen formerly neuter nouns in Romani that had been reassigned to the same gender as in Hindi, the probability of the same change happening independ- ently in the two languages is virtually nil. The most likely explanation of these parallel changes is that Romani was spoken in India at the turn of the second
3 As mentioned earlier, the newly substituted version of the Supplementary Materials places the
millennium, with the loss of the neuter gender and the reassignment of formerly neuter nouns to masculine or feminine genders occurring before the language split off from the rest of the Indo-Aryan family. Thus, the Romani exodus must be dated to around 1000ce.
A potential problem with using the gender system to date the Roma exodus from India is the fact that not all MIA languages have lost the neuter gender. Marathi and Oriya, for example, have retained the three-way gender system. It is notable that both Marathi and Oriya are spoken at the southern edge of the Indo-Aryan realm. Further south, many of the Dravidian languages, such as Kannada and Tamil, have three-way gender systems. That the number of genders in a language may result from linguistic contact with neighboring languages is evident from the fact that Kolami, a Dravidian language spoken farther north and surrounded by Indo-Aryan languages, has a two-way gender system.
But fortunately for historical linguists, Romani exhibits a number of other phonological and morphological properties that characterize it as a NIA language (Matras 2002).4 These include such grammatical developments as the loss of the elaborate nominal case endings present in Old and Middle Indo-Aryan and their reduction to a simple opposition between nominative and oblique. For example, the word‘boy’ in Romani has only two forms: the nominative raklo and the oblique rakles-, comparable to the Hindi la
_rkā and la
_rke-, respectively. Other case-like meanings are expressed by former post- positions, repurposed as clitics, and attaching to the oblique form (some of these clitics have been subsequently grammaticalized into suffixes in Romani). Another development shared by Romani with other NIA languages is the simplification of certain consonant clusters, as in MIA sappa ‘snake’ > Romani sap, and MIA ratta‘blood’ > Romani rat. Finally, Romani shares with its NIA brethren such as Hindi the disappearance of the MIA past tense conjugation and the substitution of the past participle, still visible in some dialects of Romani. The past participle shows agreement in gender, as in ov gelo ‘he went’ vs. oj geli ‘she went’. These forms are comparable to the Hindi vo gayā ‘he went’ vs. vo gayī ‘she went’. These shared patterns indicate that an earlier form of Romani was part of the Indo-Aryan dialect continuum during the transition period to the NIA phase, which took place in medieval times, perhaps as early as the eighth or ninth centuryce or as late as the tenth century ce (for further details, see Matras 2010: 32–33). However, it is absolutely certain from this grammatical evidence that Romani did not split off from the rest of the Indo-Aryan tree as early as 1500bce (3,500 years ago) or even 500 bce (2,500 years ago).
4
We thank Yaron Matras for a most helpful discussion of Romani.
Russian, another language known for its relatively high level of borrowing, is also given an erroneously early differentiation date. According to the Gray– Atkinson model, Russian split off from the rest of the East Slavic tree (which erroneously includes Polish in the Gray–Atkinson model, as discussed in
Chapter 4) approximately 1,000 years ago (this date did not change in the newly substituted set of results). However, as Sussex and Cubberley (2006: 80) put it,“the East Slavs were culturally, religiously and linguistically coher- ent” at least “until the sacking of Kiev by the Tartars in 1240”. Geopolitically, circa 1000ce, we can differentiate East Slavic principalities, such as Polotsk Principality in what is now Belarus, Volynia Principality in today’s Ukraine, and Rostov-Suzdal’ Principality in what was to become northern Russia. Some of these principalities, however, span the modern Russia–Ukraine border: for example, Chernigov Principality centered around the city of Chernigov in what is now Ukraine but also included lands around Kursk, which are now Russia. The three peoples, Russians, Ukrainians, and Byelorussians, emerged as linguistically, culturally, and geopolitically distinct groupings centuries later. Linguistically, Russian emerged as a distinct language from Belarusian and Ukrainian chiefly as a result of two historical developments that postdate the timing of the Russian split in the Gray–Atkinson model by about 400 years. The first development was the gradual absorption of what is now Belarus and Ukraine into the Grand Duchy of Lithuania and later the Kingdom of Poland, a process that began in 1386. The second set of events that set Russian on a different course vis-a-vis Belarusian and Ukrainian was the incorporation into the Russian state of the Novgorod Republic, which extended from the Baltic Sea to the northern Ural Mountains, where a distinct- ive dialect of (Old) Russian had developed. The Russian annexation of Novgorod began in 1478 with a series of wars between the Grand Duchy of Moscow and the Novgorod Republic. In subsequent years, a large part of the republic’s population was resettled elsewhere, and peasants from Moscovy were transplanted to the Novgorod lands. As a result, elements from the Novgorod dialect were incorporated into Russian (but not into the vernaculars of the Lithuanian Rus’), as discussed by Andrey Zaliznyak.5 For example, recall fromChapter 4(discussion surroundingTable 4.2) that the dialect of Old Novgorod did not undergo the so-called Second Slavic Palatalization, retaining the original /k, g, x/ in place of the innovative /ts, z, s/ in roots such as kѣl- ‘whole’ and xѣr- ‘gray’. Nor did the Second Slavic Palatalization apply in Old Novgorod across morpheme boundaries, in locative case forms of nouns such