How Do Languages Change Through Time?

It is now necessary to ask if linguistic analysis can provide chronological data independent of those derived from the archaeological record. The answer is a little ambiguous. Linguists reconstructing the history of a language family can generally only go back in time as far as the proto-language at the base of the phylogeny. The dispersal of this proto-language will represent a punctuation, an erasure of any previous linguistic pattern, although traces of previous patterns can sometimes survive in enclaves or so-called "linguistic isolates." Going beyond the family proto-language level takes us into the level of macrofamilies, with lots of attendant controversy owing to the eroded nature of the record and its inherent ambiguity.

Linguistic analysis, in fact, does not yield time depth easily, as will be seen from a perusal of a recent compilation of papers on this topic (Renfrew et al. 2000). Ancient written languages on a world scale are too rare (and too recent) to be of very much assistance in throwing light on the periods under investigation in this book. Some can give rule of thumb ideas about rates of change, derivable for instance by comparing Coptic with Ancient Egyptian, Romance languages with late classical Latin, or Mandarin with Old Chinese. We can also use the archaeological record quite precisely in island situations where we can be fairly sure that only one population, and that ancestral to the present population, has been in occupation. On these grounds, the Vanuatu languages, for instance, can only have been developing for about 3,000 years, since Vanuatu was first settled then. Maori has closer to 800 years since its arrival in New Zealand. Yet these year counts by themselves do not get us very far in a comparative sense, unless we assume that there is a constant rate, like a mutation rate, by which languages change their vocabularies through time.

Claims for such a regular rate of language change, especially in core vocabulary (common and universal words in all languages, not culturally specific words), have been made by a number of linguists. The most famous is the glottochronological formula developed in the 1950s by Morris Swadesh, which assumes random corevocabulary replacement in any language of 19.5

percent per 1,000 years (this figure being derived from a 200-word list applied to Romance languages). It is not necessary to examine the mathematical foundations of glottochronology here, but most linguists, at least those who do not reject it altogether, regard it as most useful for the past 500-2,500 years. Like radiocarbon dating, the more one goes back in time the less the quantity of datable material that remains. Linguists who use glottochronology and regard it as relatively accurate include Ehret (1998, 2000, 2003) for African language families, Kaufman (1990a) for American families, and Nichols (1998b), who states that it can be used successfully for language history in general after 6000 BP. As Kaufman (1990a: 27-28) states:

The fact remains that when applied as it should be applied, glottochronology seems to agree remarkably well with linguistic inferences arrived at by other means, such as branching models based on shared non-trivial innovations or absolute chronology derived from dated monuments.

Not all linguists agree with this rather enthusiastic perspective. Observations that languages seem to have changed at different rates, some being conservative, some innovative, were made almost from the start. Some linguists pointed to a common and intriguing habit in many tribal societies known as word tabooing, which dictates that a sound that occurs both in an everyday word and in the name of a dead person must no longer be uttered. The everyday word thus has to be changed and so the lexicon as a whole can change quite quickly, at least in theory (e.g., Kahler 1978; Chowning 1985). On another tack, Malcolm Ross (1991; also Blust 1991) suggests that, in a dispersal situation, the stay-at-home languages will tend to be more conservative than the migrating ones owing to social dislocation and founder effects; small migrant groups tend to lose and modify linguistic resources more rapidly than the larger and more stable populations back in the homeland.

Perhaps the strongest critic ofglottochronology as applied to Austronesian languages has been Robert Blust (2000b), who compared a number of modern Malayo-Polynesian languages within the Austronesian family with their reconstructed common ancestor, Proto-Malayo-Polynesian (PMP). Logically, if all languages change their basic vocabularies at a uniform rate, then all daughter-languages derived from a common ancestor should be equally different from that ancestor, given that they have each been descending from it for the same length of time. Blust used a 200-word list and was able to show

that some Malayo-Polynesian languages, especially certain Polynesian languages and Malay, retain a large number of PMP cognates and have thus had conservative histories. Other languages, mostly in western Melanesia, retain very few PMP cognates and are thus innovative. If one applies glottochronology to these innovative languages one comes up with the erroneous conclusion that the entire Austronesian language family originated in Melanesia, a conclusion completely at odds with the mainstream comparative tradition of linguistics that makes a homeland in Taiwan almost certain.

The main reasons for this puzzling situation seem to be that Austronesianspeaking societies in western Melanesia formed small social groups in which language differences were emphasized as social markers, and many were in intensive contact with speakers of completely unrelated Papuan languages and borrowed frequently from them (Capell 1969; Dutton 1994, 1995; Dutton and Tryon 1994; Ross 2001). The Polynesian and Malay languages existed in linguistically less diverse environments and were spoken by larger and more cohesive groups. The implications of all this are that lexicostatistics documents variation in retention rate, not true phylogeny.

So where does this leave glottochronology? Obviously, languages that have had histories similar to those of the Romance languages might have had similar rates of change, and this seems to be true of Polynesian languages and Malay. Melanesian languages have not had such histories, and once one domino falls it tends to wobble the rest. For deeply prehistoric societies we cannot easily know what the precise linguistic environment might have been, so we can never really know if a given glottochronological date is right or wrong. Nevertheless, in the next chapter I will refer to glottochronological dates in some instances since, en masse, they do seem to show some overall correlation with archaeologial dates for the beginnings of agriculture, at least as far as the major language families with agriculturalist proto-languages are concerned (Bellwood 2000c). There may not be precision here in all circumstances but there is a trend, in the sense that Afroasiatic, Sino-Tibetan, and Uto-Aztecan, to give three examples from many, have glottochronological time depths which tend to agree quite well with the time depths for agriculture in the likely homeland areas. We return to the details later.

Macrofamilies, and more on the time factor

Although language families are recognized as genetic groups by linguists, it is very difficult to reconstruct much deeper genetic groups comprising several families, even though comparative linguistic principles remain the same regardless of whether one is working within or beyond the individual family (Hegedus 1989; Michalove et al. 1998). This very characteristic of language families, that they cohere within but not convincingly without, supports the view of rapid punctuational origins during which earlier linguistic landscapes were erased by dispersal (Dixon 1997; Aikhenvald and Dixon 2001:9). In addition, language families are not only discrete, but they also appear to have fairly limited time depths, as discussed above. According to Johanna Nichols (1998b), they can only retain genetic identity for about 6,000 to 10,000 years. But I would ask if this is a real statistical limit, or an epiphenomenon of the fact that virtually all major language families have for some reason radiated fairly explosively within precisely this time period, prior to which time such radiations tended hardly to occur. The mere fact that reconstruction at the macrofamily level leads to so much acrimonious and inconclusive debate, when logically it should not do so if language family evolution has always been even and regular, supports the idea of relatively recent starburst-like episodes of language family dispersal from homeland regions. In such cases, any foundation relationships that might exist between different families will be rake-like and always ambiguous.

The answers to the confrontations that divide linguists at this deep level of reconstruction are unlikely to come from within linguistics itself. Multidisciplinary observations, especially from the archaeological record, can perhaps provide some essential help. For instance, Colin Renfrew and I were suggesting over a decade ago that many language families originated in and spread from a small number of specific regions where agriculture began early in the Holocene (Bellwood 1989; Renfrew 1991). This is because farming is a more efficient driver of language family dispersal in previously inhabited landscapes than hunting and gathering (allowing, of course, that hunters can spread far and rapidly if there is virtual prior depopulation). These agriculturalist language families, on geographical grounds, might share

homeland relationships of a macrofamily nature, even if clear demonstration of such will always be highly elusive.

Thus, language inter-family relationships, even if only reflecting early borrowing and propinquity of homeland rather than true common ancestry, could have firm foundations in historical events. Before trying to reconstruct such events, however, it is necessary to consider in more detail how languages replace and influence each other through time and space.