「#1871. 言語と人種」 ([2014-06-11-1]) の続編．先の記事では「言語＝人種」という「俗説」に光を当てた．言語と人種を同一視することはできないと主張したわけだが，もっと正確にいえば，両者を「常に」同一視することはできない，というべきだろう．常に同一視する見方に警鐘を鳴らしたのであって，イコール関係が成り立つ場合もあるし，実際には決して少なくないと思われる．少なくないからこそ，一般化され俗説へと発展しやすいのだろう．
　近年の遺伝学や人類学の発展により，ホモ・サピエンスの数万年にわたるヨーロッパなどでの移動の様子がつかめるようになってきたが，それと関係づける形で印欧語の派生や展開を解釈しようという動きも出てきた．このような研究は，上記のような俗説に警鐘を鳴らす陣営からは批判の的となるが，言語と人種をペアで考えてもよい事例をたくさん挙げることにより，この批判をそらそうとしている．
　McMahon and McMahon (19--20) もそのような論客である．一般的にいって，遺伝子と言語の間に相関関係がないと考えるほうが不自然ではないかという議論だ．

. . . since we are talking here about the histories of populations, which consist of people who both carry genes and use languages, it might be more surprising if there were no correlations between genetic and linguistic configurations. The observation of this correlation, like so many others, goes back to Darwin . . . , who suggested that, 'If we possessed a perfect pedigree of mankind, a genealogical arrangement of the races of man would afford the best classification of the various languages now spoken throughout the world'. The norm today is to accept a slight tempering of this hypothesis, such that, 'The correlation between genes and languages cannot be perfect . . .', because both languages and genes can be replaced independently, but, 'Nevertheless . . . remains positive and statistically significant' . . . . This correlation is supported by a range of recent studies. For instance, Barbujani . . . reports that, 'In Europe, for example, . . . several inheritable diseases differ, in their incidence, between geographically close but linguistically distant populations', while Poloni et al. . . . show that a group of individuals fell into four non-overlapping classes on the basis of their genetic characteristics and whether they spoke an Indo-European, Khoisan, Niger-Congo or Afro-Asiatic language. In other words, there is a general and telling statistical correlation between genetic and linguistic features, which reflects interesting and investigable parallelism rather than determinism. Genetic and linguistic commonality now therefore suggests ancestral identity at an earlier stage: as Barbujani . . . observes, 'Population admixture and linguistic assimilation should have weakened the correspondence between patterns of genetic and linguistic diversity. The fact that such patterns are, on the contrary, well correlated at the allele-frequency level . . . suggests that parallel linguistic and allele-frequency change were not the exception, but the rule.

　McMahon and McMahon とて，言語と人種の相関係数が1であるとはまったく述べていない．0というわけはない，そこそこ高い値と考えるのが自然なのではないか，というほどのスタンスだろう．それはそれで間違っていないと思うが，「常に言語＝人種」の俗説たることを押さえた上での上級者向けの議論ととらえる必要があるだろう．

　・ McMahon, April and Robert McMahon. "Finding Families: Quantitative Methods in Language Classification." Transactions of the Philological Society 101 (2003): 7--55.

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