Mosquitoes May Have Been Feeding on Homo erectus 1.8 Million Years Ago
Nearly two million years ago, as the first members of the genus Homo expanded into the rainforests of Southeast Asia, they encountered a landscape teeming with primates, predators and insects, including mosquitoes that may have already evolved a preference for their blood.
A new genetic study published in Scientific reports estimates that this transition to human diet occurred between 2.9 and 1.6 million years ago, overlapping with the arrival of early hominids such as Homo erectus in the region around 1.8 million years ago. This means that this group of mosquitoes began targeting humans more than a million years before similar preferences were thought to have evolved in the main African malaria vectors.
How mosquitoes evolved to feed on early hominids
Of approximately 3,500 known species of mosquitoes, only a small fraction strongly prefer to feed on humans. But this preference is what makes some species particularly effective at spreading diseases like malaria. Mosquitoes that constantly seek out human hosts are much more likely to transmit pathogens between people.
The species examined in the new study belong to the Anopheles leucosphyrus group, a group of mosquitoes from Southeast Asia that includes known spreaders of malaria. To understand how their host preference evolved, the researchers sequenced the DNA of 38 mosquitoes representing 11 species. These samples were collected across Southeast Asia between 1992 and 2020.
Using genetic data, mutation rate estimates and computer modeling, the team reconstructed the group’s evolutionary history. Their analysis suggests that the shift to human diet once occurred within this Sundaland group – a prehistoric landmass that once linked parts of the present-day Malay Peninsula, Borneo, Sumatra and Java during periods of lower sea levels.
Before this transition, the ancestors of mosquitoes fed primarily on non-human primates, which were abundant in the region’s rainforests.
Learn more: Cases of mosquito-borne Chikungunya virus increase due to travelers and climate change
When mosquitoes started targeting the first humans
The timing of this operation closely matches estimates regarding the arrival of Homo erectus in Southeast Asia. It also predates the arrival of modern humans in the region, 76,000 to 63,000 years ago.
Together, the results indicate that adaptation to human hosts coincided with early hominid populations rather than modern human societies.
Previous research has shown that changes in mosquitoes’ host preferences involve alterations in genes that control odor detection. Mosquitoes rely heavily on scent to locate their hosts, distinguishing between species based on chemical cues. Moving from tracking primate odors to specialization in humans likely required multiple genetic changes—a process that may have occurred gradually as early hominid populations became established and more predictable food sources became available.
The researchers propose that Homo erectus it would have had to be present in substantial numbers to create constant evolutionary pressure favoring mosquitoes that were better able to detect and feed on humans.
What mosquito DNA reveals about early humans
The implications extend beyond mosquito biology. The researchers say their findings provide independent, non-archaeological evidence supporting the limited fossil record of the early arrival of hominids in Southeast Asia.
The study also highlights how early this adaptation occurred. In Africa, the mosquito lineages that gave rise to the main vectors of malaria, such as Anopheles gambiae And Anopheles coluzzii They are thought to have developed a strong preference for humans around 509,000 to 61,000 years ago, much later than the Southeast Asian shift estimated here.
Since fossils from the earliest phases of hominid expansion into Southeast Asia remain rare, evolutionary changes in other species may offer additional clues about when ancient humans first established themselves in the region. In this case, the mosquito’s DNA preserves evidence that humans became a reliable host for malaria-carrying insects much earlier than previously thought.
Learn more: Mosquitoes can smell when someone has drunk a beer and even prefer the blood of beer drinkers
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