Collaborating with a Princeton-led international team, Professor Kun-Hsien Tsai of National Taiwan University and alumnus Kai-Ti Yu contributed to a Science study that fundamentally rewrites the evolutionary history of the “London Underground mosquito” (Culex pipiens form molestus) and clarifies its role in West Nile virus transmission. Contrasting with the textbook narrative that these pests are recent products of modern urbanization, genomic analysis reveals they evolved to coexist with humans 1,000 to 10,000 years ago in early agricultural societies, likely originating in the Mediterranean. The team’s local investigation further identified distinct genetic divergences between mosquito populations in northern and southern Taiwan, indicating multiple introductions or complex genetic exchanges. These findings underscore significant public health risks, as urban environments foster genetic mixing that increases non-specific biting behaviors and viral spillover potential, prompting calls for integrated evolutionary biology research and strengthened vector surveillance policies.