Paternal Words, Maternal Sounds: Asymmetrical Gene–Language Co-evolution in Indo-European Languages

How languages are transmitted across generations has long been a central question in research on human migration and linguistic origins. One long-standing debate concerns whether language inheritance is more strongly associated with maternal or paternal ancestry. The mother tongue hypothesis proposes that languages are primarily transmitted along maternal lines, whereas the father tongue hypothesis argues that languages tend to follow paternal lineages because linguistic patterns often show stronger correlations with the Y chromosome than with mitochondrial DNA. For many years these two perspectives appeared to contradict each other. Research on Indo-European populations, however, suggests that the relationship between language and ancestry is more complex than either hypothesis alone implies.

To clarify this issue, researchers conducted a large-scale quantitative study involving 34 modern Indo-European populations, examining both genetic and linguistic data. The genetic component focused on haplogroups of the Y chromosome and mitochondrial DNA, representing paternal and maternal histories respectively. Rather than relying on traditional language family trees or classification schemes, the study analyzed two distinct linguistic dimensions: lexical systems and phonemic systems. These two components reflect different aspects of language evolution. Lexical data were drawn from a public dataset compiled by Michael Dunn, while phonemic information came from the PHOIBLE database, which catalogues the sound inventories of languages. Because vocabulary and sound systems often follow different evolutionary paths, separating them allows a more detailed investigation of how languages change over time.

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