Mosquitoes are the deadliest animal on the planet, killing hundreds of thousands of people every year by transmitting malaria, dengue fever and a host of other deadly diseases. Understanding how insects first developed a taste for human blood has long fascinated scientists and could help us better fight the spread of mosquito-borne disease. Now, a new study suggests that some mosquitoes’ thirst for human blood may be truly ancient, stretching back as far as 1.8 million years ago—a time when our ancient human ancestor Homo erectus may have flourished.
In the study, published Thursday i Scientific reports, an international team of researchers analyzed DNA from 40 mosquitoes from 11 species of Anopheles leucosphyrus group found in Southeast Asia. What makes this group of mosquito species so special is that some of the species have a strong preference for human blood, while others mostly feast on other primates, such as monkeys, gibbons and orangutans, says Upasana Shyamsunder Singh, postdoctoral fellow at Vanderbilt University and lead author of the study.
The team calculated that the mosquitoes probably developed their “anthropophily” – their taste for human blood – at some point around 2.9 million to 1.6 million years ago. This overlaps with the same period as some researchers believe H. erectus, an early hominin, arrived in the region.
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“The transition to human feeding was much older than we expected, and therefore cannot have been a response to the arrival of anatomically modern humans,” says Catherine Walton, a study co-author and a senior lecturer in Earth and Environmental Sciences at the University of Manchester in England.
For the mosquito to have made a transition from other primates to hominins, ancient people such as e.g H. erectus “must not only have been present in this place and at this time, but abundantly,” she says.
The results are not only relevant to researchers studying human evolution; they are also an important signal for epidemiologists who want to understand mosquito-borne diseases. These insects are still evolving and humans are increasingly entering wild areas – more mosquitoes may continue to adapt to prefer feasting on us over other animals.
“We are effectively creating new selective pressures, and we should expect mosquitoes to respond to these,” says Walton.
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