Although most of the roughly 3,500 mosquito species don’t feed on human blood, the Aedes aegypti is one of the worst. Its bite infects millions of people – especially young children – with yellow fever, dengue and Zika, causing tens of thousands of deaths each year.
By comparing their genes, the researchers determined that the Aedes aegypti mosquitoes probably evolved from an ancestral species on islands in the southwest Indian Ocean about 7 million years ago.
[Evolutionary biologist John Soghigian] said the Aedes aegypti was traditionally seen as a forest species that had adapted to human settlements, but the new research suggested it first adapted to survive the varied environmental conditions of the islands.
“This is a mosquito that may have already been highly adaptable to diverse habitats when it reached Africa, and so that could explain why [it] became such an important vector and pest to humans,” he said.
The study also found that mosquitoes from the dry Sahel region of Africa – the semi-arid zone between the Sahara desert and wetter regions further south – consistently preferred biting humans… Those two factors indicated the Aedes aegypti had evolved in densely populated areas in a dry region like the Sahel to bite humans – and so some mosquito-borne diseases could increase if the climate became drier and as more people moved to live in cities, [evolutionary biologist Carolyn McBride] said.