Genetics

One of the more stunning proposals associated with Greenberg's (1987) classification of the native American languages was the notion that further evidence for the three linguistic families identified by Greenberg (Eskimo-Aleut, Na-Dene and the superfamily Amerind) was to be found in the genetic and dental records of the various populations.  Specifically, Greenberg, Turner and Zegura (1986) argued that each language family correlated with a distinct dental morphology and a distinct set of classical genetic markers in three unique clusters.  These three groups were said to have migrated into the Americas thousands of years apart, which accounted for their vast linguistic diversity.  In a recent paper Hunley and Long (2005) used mtDNA sequences to show that the patterns of variation in the genes and languages of the relevant populations disagree, and that a principal argument for the three-migration theory has been taken out of the debate.  In another paper, Nettle and Harriss (2003) argue against Cavalli-Sforza, Menozzi and Piazza's (1988) assertion that congruence can be established between genetic and linguistic distance and between genetic and linguistic evolution.  They argue that such parallelism can be correlated only under highly specific conditions, such as when there have been large-scale demic diffusions followed by relative sedentism in the subsequent period, and not as a matter of routine.  This finding correlates positively with Dixon's punctuated equilibrium model (1997).  Similar cautions about the relationship between genes and languages are being voiced in many quarters (elaborately summarized by Bellwood 2005), all the while keeping the link between the two disciplines a vital one.