Evidence from historical linguistics confirms that language contact and phonological drift play significant roles in shaping and diversifying the consonant inventories of Indo-European languages from their proto-language origins.
The claim is specific, empirical, and testable within historical linguistics. Papers [3] and [11] directly discuss how language contact and phonological drift influence sound inventories and historical divergences within the Indo-European language family. The remaining papers are either about word order, syntax, unrelated language families, or general evolutionary dynamics without specifically supporting or refuting the exact claim regarding Indo-European consonant inventories. Thus, the balance of evidence clearly supports the claim.