What GVPSNA Got Right (And What Others Get Wrong)

December 14, 2007

Since I have been critical of the use of historical linguistics in Genetic Variation and Population Structure in Native Americans (PLoS Genetics) (GVPSNA), it’s only fair that I point out that they did get one major point very much correct: the contingent nature of the correspondence between genetic relatedness and linguistic relatedness. In Anthropology, this fundamental observation goes at least as far back as Boas, who observed that languages, cultures, and populations each have potentially independent trajectories through time and space. Of course, language, culture, and populations may remain bundled together for periods of time, but this is a fact to be determined by empirical investigation, and cannot be assumed at the outset.

GVPSNA presents a number of intriguing examples of the lack of tidy correspondence between genetic and linguistic relatedness, but let me focus on just one: the fact that the Arawak language-speaking Wayuu are apparently more closely genetic related to the Chibchan language-speaking groups to the west than they are than to the Arawak-speaking Piapoco to the south.

What could this mean? Could this be evidence for Arawak cultural imperialism — an Arawak linguo-cultural takeover — as Max Schmidt’s theory of Arawak expansion proposes? The data presented in GVPSNA are far too spotty to permit us to reach any conclusions (genetic data are only presented for two Arawak languages and five Chibchan languages), but the hints are tantalizing, and the direction for further research is clear.

As it turns out, however, not all geneticists are clear on the loose connection between genetic and linguistic relatedness. Let me take an areally relevant example: a 2005 article in Current Anthropology, by Francisco Mauro Salzano, Mara Helena Hutz, Sabrina Pinto Salamoni, Paula Rohr, and Sidia Maria Callegari-Jacques, entitled Genetic Support for Proposed Patterns of Relationship among Lowland South American Languages (GSPPRLSAL).

The opening paragraph gives a sense of the authors’ perspective:

Comparison of different sets of markers to unravel the past of human populations is an established procedure in both anthropology and genetics. Language characteristics can be easily quantified, and the field of comparative linguistics has a respectable past [citations cut]. Therefore, it is only natural that evolutionary geneticists have turned to linguistics to evaluate the population relationships that they have been obtaining with genetic markers.

Well, I don’t know whether such a move is “natural,” but I suspect anyone who follows this strategy is naïve. Linguistic classification simply cannot tell us anything about the genetic relationships between the populations speaking the languages in questions. GVPSNA, not to mention Boas long before, makes this point quite clearly.

In any event, the goal of the research reported in the paper is to use genetic data to evaluate three different classificatory proposals (due to Greenberg, Loukotka, and Aryon Rodrigues), linking the Arawak, Carib, Gê, and Tupí families:

The testing of the hypotheses concerning language relationship patterns of Greenberg, Loukotka, and Rodrigues was performed using genetic data by means of a method developed by Cavalli-Sforza and Piazza …

And off they go! Data is presented, algorithms are mentioned, and conclusions are drawn. However, just as linguistic classification tells us nothing about genetic relatedness, neither does genetic relatedness of populations tell us anything about linguistic relatedness of the languages the populations speak. (Incidentally, I find it incongruous that a group of Brazilian geneticists, living in a country of mixed African, European, and Native American heritage, in which Portuguese is the dominant language, could, for a moment, imagine that there is any kind of tidy correspondence between genetic and linguistic relatedness.)

And that, really, should be the end of the post. GVPSNA got an important point about the contingent correspondence between genetic and linguistic relatedness right, and, as we can see, this point is not obvious to everyone working at the intersection of genetic and linguistic classification. Kudos to the authors GVPSNA.

But what of the conclusions of GSPPRLSAL? According to the authors:

Rodrigues’s hypothesis was the only one not rejected. Other possible tree arrangements representing the relationships among the language families not considered by the three linguists were identified but are irrelevant to the present inquiry.

But then a little later they summarize their results as follows:

Genetic data support other tree configurations besides those proposed by Greenberg, Loukotka, and Rodrigues. This is not surprising, because different kinds of data may produce somewhat different estimates of the history of the populations. Among the three possibilities proposed by these scholars, that of Rodrigues has the best genetic support.

Hmm. Ok, so, of the three initial proposals, Rodrigues’ fares best, but the genetic data actually supports totally different classifications as well. I fail to understand why “this is not surprising”, or what the comment about “different kinds of data … produc[ing] different estimates of the history of the populations” means. Maybe its my ignorance about genetics speaking, but something smells fishy here.

In any event, it seems to me that if one buys the utility of genetic data in supporting linguistic classification (and there is no good reason to do so in the opinion of most historical linguists, I believe), then the fact that Rodrigues’ proposal is only one of a number of logically possible classifications supported by the genetic data should be a big deal! We don’t even know if Rodrigues’ classification fares better than some of the unmentioned alternatives.

Of course, at the end of the day, none of this really matters, because the genetic data tells us nothing about linguistic classification.

The fact that articles like this and GVPSNA get published in solid journals with major linguistic blunders in them just makes me wonder about the peer review process. Doesn’t it occur to editors that if they are reviewing an article involving linguistic classification that it wouldn’t be a bad idea to get a historical linguist involved?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: