Question

Read the passage below:

For decades, urban evolutionary ecologists operated under the assumption that behavioral adaptations in synanthropic songbird species—such as shifts toward higher-frequency vocalizations in response to anthropogenic acoustic clutter—were purely phenotypic plastic responses driven by immediate auditory masking. However, recent genomic analyses of urban populations of Parus major have revealed distinct allele frequency shifts in genes regulating vocal tract morphology and neuromuscular control. Proponents of this micro-evolutionary framework argue that prolonged exposure to low-frequency noise exerts directional selection, favoring genetic variants that encode higher baseline pitch. Critics of the genetic selection model contend that these genomic variations are merely neutral evolutionary drift resulting from population bottlenecks associated with urbanization. Yet, this counterargument overlooks the fact that homologous allele shifts have been documented independently across geographically isolated urban populations facing identical acoustic pressure. Thus, while phenotypic flexibility undoubtedly plays an initial acclimatization role, acoustic pollution acts as a potent agent of evolutionary divergence.

In the context of the passage as a whole, the sentence 'Yet, this counterargument overlooks the fact that homologous allele shifts have been documented independently across geographically isolated urban populations facing identical acoustic pressure' serves primarily to do which of the following?